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168
CHAPTER – IV
NANO COPPER FERRITE: A REUSABLE
CATALYST FOR THE SYNTHESIS OF β, γ-
UNSATURATED KETONES
169
Nano Copper ferrite: A reusable catalyst for the synthesis of β, γ-
Unsaturated Ketones
SECTION A: LITERATURE REVIEW
Catalysts have the remarkable property of facilitating chemical reactions
repeatedly without being consumed. Enzymes, which catalyze all aspects of cell
metabolism, are the supreme master of this art. We have used them from earlier times
for leaving bread, curdling cheese and brewing beer.
Heterogeneous catalysis plays a key role in generating the feed stock for
making the synthetic materials that we use every day, from fuels to fertilizers. New
experimental techniques have brought fresh insights into this form of catalysis, and it
now seems that there are more similarities between enzymes and heterogeneous
catalysts that initially meet the eyes.
An extensive application of heterogeneous catalysis in synthetic chemistry
can help to achieve new selective reactions to lower formation of waste and finally
render more attractive synthetic process for both environment and economic point of
view. Wender1a has described heterogeneous catalytic synthesis as “ideal synthesis” in
accordance the above.
Among the first reactions performed under heterogeneous catalysis are the
hydrogenation and, in general, the redox processes which are extensively applied in
synthetic organic chemistry. Acid - Base heterogeneous catalysis was successively
developed by exploiting the physicochemical properties of zeolities,1b clays 1c and
metal oxides.1d
Introduction to Ferrites:
The organic- Inorganic hybrid materials possess interesting functions through
the amalgamation of important properties from both components.2-5 Magnetic nano
composites possess unique physical and chemical properties compared to their bulk
counterparts due to their nano dimensions. The fast development of mobile
communication and information technology, small, inexpensive high performance
electronics devices are in high demand6. Recently, the rapid development of surface
mounting devises (SMD) using multilayer chip inductors (MLC1), which utilize
alternating coats of ferrite and electrical paste followed by co-firring.
170
Nickel ferrite nano crystals7 with octahedral structures were synthesized using
EDTA- assisted hydrothermal method under mild conditions. XRD and FTIR analyses
were used for composition and structure investigation. XRD analysis revealed a pure
ferrite phase with high crystallinity. Morphological investigations by SEM showed
octahedral nano crystals with an average size of 40 nm. The FT-IR spectrum showed υ1
and υ2 fundamental bands, corresponding to octahedral and tetrahedral sites in the
ferrite structure. Recently, it was observed that photo catalysts consist of nano
composites are efficient in utilizing visible light photons,8-12 and also observed that
such nano composite showed unprecedented high activity for photo catalytic oxidation
of water under visible light.
Jang J.S. et.al,13 describe the synthesis of Zinc ferrite(ZnFe2O4), Viz. an n-type
photo catalyst with spinel crystal structure and characterize the optical properties of
the nano crystalline zinc ferrite by using UV –Visible diffuse reflectance spectroscopy
and X-ray diffraction. Also, the photo catalytic and the photo electrochemical
performances of the material for photo current generation and CO2 production from
photo oxidation of iso propyl alcohol under visible light irradiation were investigated.
Among the nano scale inorganic materials, magnetic metal oxides and their
composites with polymers are of particular interest for their applications in various
areas like quantum computing,14 information storage media,15 sensors,16
electromagnetic wave absorption,17 modulation,18 refrigeration,19 magnetic resonance
images.20
In polymeric composites, the polymer plays the role of reducing the
aggregation of particles and imposes the upper limit on the size of inorganic particles.
The recent growth in nano materials as building blocks for general synthetic approach
to control the size and shape of inorganic nano particles. A new wet chemical method
has been reported 21, which is suitable for the direct synthesis of nano sized inorganic
oxides 22-24 in a copolymer matrix. D.R. Sharma et. al,25 reported the synthesis of a
series of nano composites of Ni-Zn ferrites in the copolymer matrix of aniline
formaldehyde and observed an interesting phase transformation including the
formation of metallic phase on pyrolysis of these materials at different temperatures
using XRD, Infrared and Mossbauer spectroscopy and transmission electron
microscopy(TEM). The spinel ferrite phase in these samples persists on heating
171
temperature to 5000C. The samples heated at 7000C, under ambient conditions, have
shown very interesting phase changes resulting the formation of Ni-Fe alloy due to the
polymer pyrolysis assisted partial reduction of spinel ferrite. Further, on heating the
sample at 7000C under Nitrogen environment results in the formation pure metallic
phase.
Liu. et al. 26 reported the high sensitivity of Cadmium ferrite(CdFe2O4) to
ethanol vapor, Reddy et. al.27 investigated Nickel ferrite(NiFe2O4) as sensor to detect
Cl2 air. Chen et al 28 revealed that Magnesium ferrite (MgFe2O4) and Cadmium
ferrite(CdFe2O4) are sensitive and selective LPG and acetylene (C2 H2).
Y. Atassi et al.29 prepared Mg-Cu-Zn ferrite through a wet synthetic method by
a self-combustion reaction directly from citrate-precursor. The synthesized powders
were sintered at 7500C for 2 hours. XRD patterns and FTIR spectra confirmed the
formation of single phase Mg-Cu-Zn ferrite after combustion. This is the first time that,
Mg-Cu-Zn ferrite is sintered at such a low temperature. The sintered process increased
the crystalinity of the solid and domain sizes. Tania Jahanbin et al 30 presented nano
crystalline nickel Zinc Ferrite (Ni0.8Zn0.2Fe2O4) has been synthesized by co-precipitation
technique. The dried powder has passed into the toroid and pellet forms, then
sintering them at sintering temperatures of 11000, 12000 and 13000C. The samples were
characterized employing X-ray diffraction, initial permeability and relative loss factor.
The initial permeability values were in the range of 10-17 due to the small particle size.
The relative loss factor was in the order 10-3 –10 -5 in the frequency range of 1 MHz to 1
GHz.
The materials of choice for many microwave applications are cubic ferrites, of
the cubic spinel ferrites two classes of materials are significant; The Mn-Zn and the Ni-
Zn ferrite materials. Mn-Zn ferrite is typically limited to frequencies <500 KHz owing
to their relatively low resistivities (0.02-20. –m) ; Ni-Zn ferrite materials have very large
resistivites (101-107 –m), high neel temperatures above 5000C and tunable magnetic
inductions making them potential candidates for much higher frequency (1-300 MHz)
applications.31 N. Rezhescu et al,32 presented some spinel ferrites, MFe204 (M=Cu,Cd
and Zn), having sub-micron grain sizes (0.1-0.7μm) were prepared by sol-gel-self
combustion and their sensing properties to reducing gases were investigated. By gas
sensitivity measurements it was found that copper ferrite(CuFe2O4) has a good
172
sensitivity to reducing gases at optimum working temperature of 3000C. Better
sensitivity to LPG of copper ferrite (CuFe2O4) cannot be explained by morphology
changes. Zinc ferrite (ZnFe2O4) having the highest porosity and largest surface area, is
sensitive to ethanol only.
The palladium catalyzed coupling reaction between aryl halide and olefins
often known as the Heck Reaction33 has become an important C-C coupling reaction in
modern organic synthesis due to the broad availability of substrates. (Aryl -Iodides, -
bromides, -Chlorides) and the tolerance to the wide range of functional groups.
In recent years, much attention has given to overcome the problems on
homogeneous ‘Pd’ catalysts, by employing many heterogeneous Pd systems,34 such as
Pd supported on different supports like carbon,35 mesoporous silica,36 zeolites,37
metaloxides,38 clays,39 polymer,40 diatomic,41 ionic liquids,42 and surface modified
nickel ferrite43. Ferrite is a family of oxide that plays an important role in the field of
heterogeneous catalyst and proved to be a suitable support44. Nickel ferrite with an
inverse spinel structure showed ferromagnetism and therefore it can be easily
separated from reaction mixture by employing an external magnetic field.
Sanjay R Borhade et al,45 presented the palladium supported on Nickel ferrite
found to be highly active catalyst for the Heck olefination of aryl iodides and activated
aryl bromides providing an excellent yield under aerobic condition & in shorter
reaction time and presented in Scheme-1.
X +
R
RPd-Nickel Ferrite
TEA , DMF
1300
X= I, Br, Cl. R= COOEt, Ph, COOH, CONH2 etc.
Scheme -1
1,2,3-Triazoles were synthesized in water using magnetically recoverable
heterogeneous Cu catalyst via one-pot multi component reaction using MW irradiation
was reported by R. S. Varma et al46(Scheme-2). The advantages of this protocol are easy
recovery of the catalyst using an external magnet, efficient recycling, and the high
stability of the catalyst renders the protocol economic and sustainable.
173
Ph
Br
+ Ph + NaN3
nano-FGT-Cu Catalyst
MW,120oC,10 min
NN
N
PhPh
Scheme -2
Y. V. D. Nageswar47 and his co-workers reported that a simple and efficient
procedure for the synthesis of diaryl selenides employing copper ferrite nanoparticle
catalyzed reaction of aryl iodides/aryl bromides with diphenyl diselenide in the
presence of base and solvent at 120 °C. The copper ferrite nanoparticles were
magnetically separated, recycled, and reused up to three cycles. This was presented in
Scheme-3
Ph I + PhSeSePhCuFe2O4 nanoparticles
KOH, DMSO, N2, 120 oC, 18hPh
SePh
Scheme -3
M.L.Kantham et al 48 presented magnetically recoverable and reusable copper
ferrite nanoparticles for asymmetric hydrosilylation of several ketones and represented
in Scheme-4. The copper ferrite nanoparticles were magnetically separated, and the
efficiency of the catalyst remains almost unaltered up to three cycles.
O
Br
CuFe2O4 nano particlesPMHS, BINAP
toulene, rt, 12h Br
OH
Scheme -4
An efficient three-component coupling of aldehydes, amines and alkynes has
been developed to prepare propargylamines in nearly quantitative yields using
magnetically separable copper ferrite nanoparticles as catalyst which was reported by
174
M.L.Kantam49.The advantage of this reaction is, it does not require any co-catalyst. It
was presented in Scheme-5
Ph ONH
Ph
++CuFe2O4
toulene, 80oC, 4hN
Ph
Ph
Scheme -5
The effectiveness of magnetic CuFe2O4 powder as adsorbent/catalyst for the
removal of azo-dye Acid Red B (ARB) from water by adsorption and subsequent
catalytic combustion was studied by R. Wu and co-workers 50. Magnetic
CuFe2O4 powder showed excellent adsorption properties towards ARB at pH<5.5, and
it could be conveniently recovered by magnetic separation technology after
adsorption(Scheme-6).
SO3Na
OH
NN
SO3Na
CuFe2O4
water, pH<5.5,
150 -300oC
SO2 + CO2 + nitrate
Scheme-6
Previous methods for the allylatioin of carbonyl compounds:
β, γ – Unsaturated Ketones are versatile synthons in the synthesis of natural
products51. In general acylation of olefins produces β, γ – unsaturated ketones, but α,
β– unsaturated ketones may also be generated52 . The synthesis is complicated by a
tendency towards prototropic rearrangement producing conjugated α, β– unsaturated
ketones53.
Y. Ishino et al54 reported that treatment of acid chlorides with allyl chlorides in
the presence of zinc dust and a catalytic amount of chlorotrimethylsilane (TMSCl) in
THF brought about highly facile and effective coupling to give the corresponding gem-
bisallylation products, 4-hydroxy-penta-1,6-dienes, in good to excellent yields. These
reactions are assumed to proceed through allylzinc intermediates generated in situ.It
was represented in Scheme 7.
175
Ph Cl
O
+Cl Zn, Me3SiCl
THF,50 o, 3h
Ph
HO
Scheme 7
Indium-mediated allylation of α-chlorocarbonyl compounds with various allyl
bromides in aqueous media gave the corresponding homoallylic chlorohydrins, which
could be transformed into the corresponding epoxides in the presence of a base was
described by J.A.Shin and co-workers55 presented in Scheme 8 . These reactions were
strongly dependent upon both the substituents at the carbon bearing chlorine and the
allyl bromides used.
Ph
O
ClBr+
PhCl
OH O Ph
In
aq.THF
DBU
THF , rt
Scheme-8
Y.-M. Zhang et al56 presnted that ytterbium can react with allyl bromide
smoothly in the presence of methyliodide to form allylytterbium bromide(Scheme 9),
which further reacts with diselenides, aldehydes and ketones to afford allylselenides
and homoallylic alcohols respectively in good yields under mild and neutral
conditions.
Br
Yb, MeI
THF, 0o
YbBr
(i) PhSePh,THF
15o, 30 min
(ii) HCl
SePh
(i) PhCHO,THF,25o,1h
(ii) HCl OH
Ph
Scheme- 9
T. H. Chan et al57 reported that commercial antimony can be used directly for
the allylation of carbonyl compounds in aqueous media in the presence of fluoride
salts.(Scheme 10)
176
Br + PhCHOaq. KF, Sb
20o, 16hPh
OH
Scheme 10
Regio- and diastereoselective carbonyl allylations of 1-halobut-2-enes with
tin(II) halides are described by Y. Masuyama et al58. In this reation, Tin(II)bromide in a
dichloromethane−water biphasic system is an effective reagent for unusual α-
regioselective carbonyl allylation of 1-bromobut-2-ene to produce 1-substituted pent-3-
en-1-ols (Scheme 11). The addition of tetrabutylammonium bromide (TBABr) to the
biphasic system produces 1-substituted 2-methylbut-3-en-1-ols via usual γ-addition
which is opposite to the α-addition without TBABr. The γ-addition to aromatic
aldehydes exhibits anti-diastereoselectivity, while that to aliphatic aldehydes is not
diastereoselective.
Br + PhCHO
A) SnBr2, CH2Cl2
H20, 25oC, 24 hrs
or
B) SnBr2, Bu4NBr
CH2Cl2, H2O, 25oC,24 hrs
Ph
OH
+ Ph
OH
Scheme 11
H.Suzuki et al59 reproted that in the presence of allyl halide, aromatic aldehydes
readily underwent a Barbier-type allylation when milled together with bismath shot to
afford the corresponding homoallyl alcohols in good yield (Scheme 12). In contrast to
the failure in solution reaction, aromatic ketones also underwent allylic carbonyl
addition under solvent-free conditions to give the expected tertiary homoallyl alcohols
in moderate to good yield
Br + PhCHOBi shot
ball mill,1.5 hPh
OH
Scheme 12
Tin-mediated allylation of aldehydes or ketones in distilled water gives rise to
the corresponding homoallyl alcohols in high yield without assistance such as heat,
supersonic and acidic media was reported by Z.Y.Wang and his co workers60 (Scheme
13).
177
Br + PhCHOSn, H2O
rt, 13hPh
OH
Scheme 13
A highly efficient electroallylation of carbonyl compounds in aqueous
electrolyte in a divided cellwith a catalytic amount of zinc consumption was reported
by J.-M. Huang et al61 (Scheme 14).
Br + PhCHO
Zn Cathode/Pt anode
NH4Cl-THF,LiClO4
H2O, 30 mA,rtPh
OH
Scheme 14
M. D. Preite et al 62 repoted that a new protocol, amenable to be used in large-
scale preparations, using an economical form of indium metal and mild warming is
reported for the Barbier allylation of aldehydes and ketones with allyl bromide in N,N-
dimethylformamide (Scheme 15).
CHOBr+
In
DMF, 40 -50oC, 2h
OH
Scheme 15
Jagir S. Sandhu et al63 described a new and efficient method for the preparation
of β,γ-unsaturated ketones has been achieved by a simple reaction of an acid chloride
with allyl and crotyl bromide and cadmium powder in absolute tetrahydrofuran
(Scheme 16)
R Cl
O
BrR1+
Cd, THF
R
O
R1
Scheme 16
An efficient procedure for the preparation of β,γ-unsaturated ketones has been
developed by a simple reaction of an acid chloride with allyl bromide and commercial
zinc dust in ether was reported by B.C. Ranu et al64 (Scheme 17) .
178
Br1.Zn , ether
2. RCOClR
O
Scheme 17
A mild and efficient method for the preparation of β,γ unsaturated ketones by
a simple reaction on acid chloride with allyl, crotyl, prenyl bromide and indium in
DMF was described by J.S. Yadav et al65 (Scheme 18).
R Cl
O
R2
R1
Br
, In
DMF / H2O
R
O
R1 R2
Scheme 18
A series of allyl ketones were synthesized from the mixture of zinc, nitrile and
allyl bromide in the presence of AlCl3 via Barbier-type reaction condition was
reported by Li-Shin Lin et al66 (Scheme 19). When crotyl bromide was used for the
allylation, only the γ-adduct was produced via the SE2′ pathway under the reaction
condition.
R CN +Br Zn/AlCl3 (4eq./0.4eq.),THF
2M HCl (5mL/ eq.)R
O
Scheme 19
Vernal J. Bryan et al67 reported that Indium mediated coupling of allylic
bromide with acyloyl-imidazoles or pyrazoles in aqueous media gives the
corresponding tertiary alcohols or ketones in good yield (Scheme 20). The reaction
provides a facile regioselective synthesis of β,γ-unsaturated ketones and its usefulness
is demonstrated by the synthesis of the monoterpene artemesia ketone.
N N
O
Ph + BrR1
In
H2ON NR
R1
O In
R
O
R1
Scheme 20
179
Yoshiro Masuyama and his coworkers68 reported that Carbonyl allylations by
allylic chlorides either with tin(IV) iodide and tetrabutylammonium iodide (TBAI) in
dichloromethane or with tin(IV) iodide and sodium iodide in 1,3-
dimethylimidazolidin-2-one at room temperature produced the corresponding
homoallylic alcohols (Scheme 21). The carbonyl allylations probably proceeded via the
reduction of tin(IV) iodide to tri iodostannate(II) species with iodide sources such as
TBAI and NaI, which led to the construction of a tin(IV)-catalytic cycle based on
regeneration of tin(IV) iodide via the transmetalation of homoallyloxytriiodotin to
homoallyloxytrimethylsilane with iodotrimethylsilane.
SnI4MI
-I2reduction
M+SnI3
Cl
-MClSnI
R
OH
RCHO
R
OSnI3H3O+
StoichiometrticMe3SiI
transmetalationcatalytic
SnI4+R
OSiMe3
R
OH
MI -I2, reduction
Scheme 21
Richard C. Larock et al69 reported that allylic mercuric iodides undergo
efficient acylation with allylic rearrangement upon reaction with acyl chlorides and
aluminium chloride to provide a convenient synthesis of allylic ketones (Scheme 22).
Artemisia ketone was prepared in two steps by this approach.
H2C=C(CH3)CH2HgI + n-C3H7COCl
AlCl3/ CH2Cl2
0oC, 10 minn-C3H7COCH2C(Cl)(CH3)2
Scheme 22
Allylations of N-benzyl and N-methyl cyclic imides were accomplished
successfully under mild Barbier type conditions using zinc metal, allyl bromide and
catalytic amount of PbBr2 was described by Sung Hoon Kim and his co-workers70
(Scheme 23). Subsequent coupling reactions with some carbon nucleophiles afforded
1,2- and 1,4-addition products in moderate to high yields.
180
Y
N
YO
OR1
R1 = CH3,CH2Ph
Y-Y: CH2-CH2,C6H4
+ BrZn
PbBr2 cat
Y
N
Y
O
OH
R1
Carbon nucleophileAlkylated product
Scheme 23
Huanfeng Jiang et al71 reported the regioselective synthesis of β, γ-unsaturated
ketones from terminal alkynes is achieved by cooperative action of tris(acetonitrile)
pentamethyl cyclopentadiene rutheni hexafluorophosphate [Cp*Ru(MeCN)3+ PF6-]
and para-toluenesulfonic acid catalysts (Scheme 24).
R + H2O
Cp* Ru(MeCN)3 + PF6- (4 mol%)
p-TSA H2O (15 mol %), dioxane, r.t
RR
O
Scheme 24
Teruaki Mukaiyama et al72 reported that various Π- allylnickel halides were
found to react with 2-pyridyl carboxylates to give β, γ- unsaturated ketones chemo
specifically in good yields (Scheme 25).
R X+
Ni(cod)2
toulene R
+NiX
X
Ni
R
+N
R'CO2
DMF R' R
O
R'R
O
+
Scheme 25
Minoru Uemura et al73 reported that reaction of acid chlorides with lithium
pentamethyl cyclopentadienide afforded the corresponding pentamethyl
cyclopentadienyl ketones in high yield. These ketones were treated with an
allylaluminum reagent to form the corresponding 3-butenyl alcohols. Removal of
pentamethyl cyclopentadiene upon heating or treatment with a catalytic amount of
trichloroacetic acid yields the corresponding β, γ -unsaturated ketones in good yields
(Scheme 26).
Ar Cl
O Cp*Li
Ar Cp*
O
Ar
OH
Cp*THF, 0oC
30 min
AlMe2
THF, -20oC1hr
toulene
reflux Ar
O
Scheme 26
Yoshiro Masuyama et al74 presented that carbonyl allylations by allylic
chlorides either with tin(IV) iodide and tetrabutylammonium iodide (TBAI) in
181
dichloromethane or with tin(IV) iodide and sodium iodide in 1,3-
dimethylimidazolidin-2-one at room temperature produced the corresponding
homoallylic alcohols (Scheme 27). The carbonyl allylations probably proceeded via the
reduction of tin(IV) iodide to triiodostannate(II) species with iodide sources such as
TBAI and NaI, which led to the construction of a tin(IV)-catalytic cycle based on
regeneration of tin(IV) iodide via the transmetalation of homoallyloxytriiodotin to
homoallyloxytrimethylsilane with iodotrimethylsilane.
R H
O
+ ClSnI4, TABI
CH2Cl2, r.tR
OH
Scheme 27
Z. Wang et al reported75 a novel mediation system, Zn-InCl3(cat.)/NH4Cl was
employed in the Barbier–type allylation (Scheme 28). As a result, the allylation with
allyl chloride in water took place smoothly under mild conditions. Various aldehydes
and even ketones could be employed to afford the corresponding alcohols in high
yields.
R1
O
R2
+R3 Cl
Zn-InCl3
sat.NH4Cl R1
OH
R2R3
Scheme 28
Akio Baba et al 76 reported that allylation of acid chlorides was achieved by
allyltributyltin in presence of catalytic amount of dibutyltin di chloride (Scheme 29).
Bu3Sn + R Cl
OBu2SnCl2
Additive
R
O
+ Bu3SnCl
Scheme 29
Samarium(II)-induced77 coupling of acid chlorides with allylic halides gave
diallylated tertiary alcohols. Monoallylated allylic ketones could not be obtained.
Cl + R Cl
OR
OH
SmI2
THF
Scheme 30
182
SECTION-B: PRESENT WORK
Introduction
Despite the advantages of homogeneous metal catalysts, difficulties in
recovering the catalyst from the reaction mixture severely inhibit their use in industry.
Heterogeneous catalysis results in easy separation and recycling of catalyst. Recent
reports reveal that magnetic nanoparticles are efficient catalysts and they can be easily
separated from reaction mixture 78. The high surface area to volume ratio of metal
oxide nanoparticle is mainly responsible for their catalytic performance79. Copper
ferrite nano material is one such reusable catalyst which shows profound catalytic
activity in organic synthesis80.
Thus it is clearly evident that the need for the development of new and flexible
protocols is required in such a way that they should be more economic and
environmentally benign. Here in, we report nano copper ferrite as a reusable catalyst,
for the allylation of acid chlorides with shorter reaction times (than reported) in good
to moderate yields. The general synthetic Scheme is presented in Scheme-I & II.
183
1a-j 3a-j
= Copper ferrite nano particle.
R = (a)C6H5,
(b) 2-ClC6H4
(c) 2-Br,5-F,C6H3
(d) 2-Br,5-F,C6H3,
(e) Furanyl
(f) 5-Phenyl,3-Methyl,4-Isoxazolyl,
(g) 5-(2,5-dichloro)Phenyl,3-Methyl,4Isoxazolyl,
(h) (CH3)3C-,(i)C11H23-(j)C15H31-,
Scheme-I: Synthesis of β, γ-unsaturated ketone using Allyl Bromide.
2a – d 4a – d
= Copper ferrite nano particle
R = (a) C6H5,
(b) 2-ClC6H4,
(c) Furanyl,
(d) – CH (CH3)2
Scheme-II: Synthesis of β, γ-unsaturated ketone employing Cinnamyl Chlorides
184
Preparation of the nano catalyst:
The catalyst is synthesized by citrate gel precursor method81. Copper (II)
nitrate and iron (III) nitrate are taken in stoichiometric proportions and minimum
amount of deionized water is added to produce clear cationic solution. Citric acid
solution is then prepared in stoichiometric ratio. Aqueous solutions with 1:1 molar
ratio of metal ion solutions are mixed and citric acid is added in equimolar ratio to the
above mixed metal ion solution. pH is adjusted to 7 by adding ammonia solution. The
aqueous mixture is kept for stirring to form a highly viscous gel. The gel is then
heated gradually up to 90oC to evolve reddish brown gases and become dried gel
which is finally treated at 350oC for 1 hr to observe whether the dry gel burnt out in
self-propagating manner to form loose powder. The finely powdered particles are
calcinated at 600oC. The powder is then characterized.
Characterization of the catalyst:
XRD studies were carried out to the synthesized nano ferrite and XRD spectrum
is presented in Fig 4.1. From the XRD data it is observed that the copper ferrites are
spinal crystals. From the XRD data, size of the copper ferrite particles is calculated by
using sheerer formulae & particle size is found to be 20 nm. This shows that the
synthesized powder has nano size crystalline. The scanning electron microscope
studies are carried out on the copper ferrite sample at 600oC, and it is presented in Fig
4.2. The TEM image was recorded and presented in Fig 4.3. The lump size with
irregular morphology is observed and it is found at 400 µm at 600oC. From the above
study we observed it possess less number of pores with smaller lump size, resulting
fine grained microstructure with respect to ferrites.
Fig 4.1: XRD Spectrum of CuFe2O4 at 600oC
185
Fig 4.2: SEM image CuFe2O4 Fig 4.3: TEM image of CuFe2O4
Results & Discussions:
In a typical experiment, allylhalide and acid chloride are mixed in presence of
catalytic amount of copper nano ferrite in stoichiometric portions using
tetrahydrofuran as solvent and stirred at room temperature. The completion of the
reaction is monitored by thin layer chromatographic technique (n-hexane and ethyl
acetate as elute). In our initials efforts to optimise the reaction condition, we screened
various solvents like tetrahydrofuran, diethylether, dichloromethane and acetonitrile
for this reaction. We found the reaction was efficient in tetrahydrofuran compared to
the other solvents tested. The results are listed in Table 1. From Table 1 it is clearly
evident that a significant decrease in yields and longer reaction times are noted for the
solvents other than THF, whereas in the presence of tetrahydrofuran the yields are
promising and shorter reaction times are noted.
Table-1: Allylation of acid chlorides under different solvent systems
S.No Catalyst Solvent Time(hrs
)
Yield*
1 CuFe2O4 THF 1.5 95
2 CuFe2O4 (C2H5)2O 3.5 78
3 CuFe2O4 Dichloromethane 6 63
4 CuFe2O4 MeCN 12 Trace
*Isolated yields
186
After completion of the reaction, the catalyst is recovered by magnetization
and washed with diethyl ether and the recovered catalyst is reused for few more
cycles. During washing with the solvent, it is clearly evident that there is no leaching
of catalyst and is confirmed by performing the reaction with the filtrate. Atomic
absorption spectroscopy is employed to determine the copper content of copper ferrite
nano particles and it is found to be 27.3%. The leaching of metal after three cycles is
found to be 0.156%. From our investigations, we observe that nano catalyst shows
excellent to good reactivity with promising yields even for the next three cycles in the
same reaction. Since, there is no observable loss in the yield percentage; the further
reusability of nano catalyst is regretted. The results are listed in table-2.
Table-2: Reusability of nano catalyst
a: Catalyst recovered by membrane filtration and washed with diethyl ether and then
by distilled water
b: yields compared to isolated products
It is noticed that in some reactions the catalyst needs co-catalysts/additives.
Some reactions need the acidic /basic workup to get the product. But here in with the
present nano sized copper ferrite catalyst; there is no need of additives, ligands, co-
catalysts and no need of activation for its reusability. The notable advantages of this
method are (i) lesser reaction times and (ii) reusable than the earlier reported methods.
The results are tabulated in Table 3.
S.No Catalyst Recoverya (%) Yeildb(%)
1 -------- 95
2 97 89
3 86 82
4 80 78
187
Table-3: Reaction times by different catalysts for the allylation of acid chlorides
* Reaction times related to the synthesis of allyl phenyl ketone.
Synthesis of β, γ-unsaturated ketone from allylbromide (3a):
In a typical procedure, allyl bromide (1 mmol) in absolute THF (5ml) is added
to a stirring suspension of copper nano ferrite (10 mol %) and stirring is continued for
30 min at room temperature. Benzoyl Chloride (1 mmol) is then added in THF (10 ml)
to the reaction mixture and then the reaction is continued for a certain period of time
as required for completion (monitored by TLC). The reaction mixture is then filtered
to separate the catalyst and the filtrate was quenched with a few drops of water and
the product is extracted with dichloromethane and the solvent is removed under
reduced pressure. Further purification is attained by column chromatography, a color
less crystalline compound is formed and recrystallized from ethanol. The pure
compound is then characterized by spectroscopic techniques.
The allyl bromide & cinnamyl chloride reacted with a wide variety of 10 acid
chlorides under the above optimized conditions and the results are summarized in
table 4. From the table 4 it is observed that when the reaction proceeded with aliphatic
long chain acid chlorides, the formation of allyl ketone was not found. It appears that
neither electronic effects nor steric effects are important factors in acylation of allyl
halides by nano catalyst. All the acylation reactions proceed with allylic
rearrangement, 82 so that the double bond was removed from the conjugation. The
mechanism, in which electrophillic attack of nano ferrite occurs at the γ carbon atom of
allylic moiety, generated insitu, will react with the acyl halides results the title
compounds. The formation of stable allyl ketone is confirmed by IR & NMR spectral
studies. In 1HNMR spectra, the chemical shift at δ 4.01-5.39, as doublet of doublet,
S.No Catalyst Time*(hrs)
1 Ni(Cod)2 [72] 15
2 Zn [64] 3
3 Cd [63] 3
4 In [65] 3
5 BuSnCl2+Additive [76] 2
6 CuFe2O4 1.5
188
confirms the presence of formation of stable olefinic bond. This indicates allylation
takes place at carbonyl carbon without any prototropic rearrangement. From 13CNMR
data the chemical shift for carbonyl carbon is observed at 162-175 ppm and 132.5-143.92
ppm corresponds to the β carbon and chemical shift at 105.07-111.82 ppm for the γ
carbon. This indicates the tolerance to the double bond.
4.1. Synthesis of allylketones from Cinnamyl chloride:
The results with allyl bromide encouraged us to extend the reaction with cinnamyl
chloride. The synthetic route is presented in Scheme-II. The reaction is done under
above said optimized conditions. The results are listed in Table 4.
Spectral Characterization of 1-(2-chloro phenyl) but-3-en-1-one (table4 entry 2) 3b:
In the IR spectrum the peaks at 1715, 1680, 3071, 776 cm-1 represents the
carbonyl group, alkenyl group, =C-H stretching and C- Cl stretchings respectively. In
1HNMR spectrum (Fig 4.4), the chemical shift at δ 3.33 -3.50 (as a broad singlet)
assigned for CH2 protons, a multiplet at δ 4.76-5.11 for the CH proton, a doublet of
doublet at δ 4.23 for the =CH2 protons and aromatic protons appeared at δ 7.42 -7.93
confirms the formation of compound. In 13 C NMR (Fig 4.5) chemical shifts at δ 166.64,
132.30, 131.70, 131.38, 130.73, 126.96, 119.67, 37.40 were in accordance with the
structure.
Spectral Characterization of 1-(5-methyl-3-phenyisoxazol-4-yl) but-3-en-1-one (table
4 entry 6) 3f:
After completion of the reaction, the crude product was characterized by
advanced spectroscopic techniques. The IR spectrum of compound 3f was presented
in Fig 4.6. From the figure, the peaks at 1719, 1599, 3108, 1678 & 1058 cm-1 corresponds
to carbonyl group, stretching of C=C of allyl group , =C-H group stretching , C=N
stretching of isoxazole moity and C-O-N group respectively . In 1HNMR spectrum
(Fig 4.7) chemical shift at δ 8.18-8.22 represents the aromatic protons, a doublet at δ
3.67 corresponds to the CH2 protons attached to the carbonyl group, a characteristic
multiplet observed at δ 6.29 for the allyl proton (=CH), a doublet of doublet at δ 4.96-
5.04 for the end methylene protons, and a singlet at δ 2.49 for the methyl proton. From
the 13CNMR spectrum (Fig 4.8) chemical shifts at δ 174.9, 162.16, 160.53, 132.88, 131.09,
129.15, 128.38, 126.87, 109.92, 42.30, 12.82 confirms the formation of compound.
189
Fig 4.4 1H NMR spectrum of 1-(2-chloro phenyl) but-3-en-1-one (3b)
190
Fig 4.5 13C NMR spectrum of 1-(2-chloro phenyl) but-3-en-1-one (3b)
191
Fig 4.6 IR spectrum of 1-(5-methyl-3-phenyisoxazol-4-yl) but-3-en-1-one 3f
192
Fig 4.7 1H NMR spectrum of 1-(5-methyl-3-phenyisoxazol-4-yl) but-3-en-1-one 3f
193
Fig 4.8 13C NMR spectrum of 1-(5-methyl-3-phenyisoxazol-4-yl) but-3-en-1-one 3f
194
Table-4: Synthesis of allyl ketones Using copper ferrite nano particles
S.NO R - COCl PRODUCT TIME(hrs)
1
2
3
4
5
6
7
8
10
Cl
Br
F
Br
MeO
O
N
O
C6H5
N
O
C6H3(2,5-Cl)
C(CH3)3
H23C11
C15H31
O
1.5 95
1a3a
OCl
O
Br
F
O
Br
MeO
O
O
N
O
C6H5O
N
O
(Cl-5,2)C6H3O
C(CH3)3
O
ALLYL HALIDE
9
1b 3b
1c3c
1d 3d
1e 3e
1f3f
1g3g
1h 3h
1i
NR
1j
NR
Br
2.3 86
2.0 84
3.081
2.575
3.0 82
3.580
3.075
YIELD(%)
195
11
12
13
Cl
O
O
2a 4a
2b
Cl
OCl
O
O
(CH3)2CH(H3C)2HC
O
2.0 81
2.5 80
2.5 75
3.0 7214
4b
2c
4c
2d4d
*Yields compared to isolated products and characterized by IR &NMR studies
compared with authentic samples
NR: No Reaction
196
Conclusions
In conclusion, we report here for the first time an efficient protocol in the
synthesis of β, γ-unsaturated ketones using copper ferrite nano material. The notable
advantages are inexpensive, heterogeneous reusable catalyst; mild reaction conditions,
high yields of products, shorter reaction times, no isomerization during the reaction
and easy workup.
This work was published in “Journal of Chemical Sciences” Vol. 124, No. 3, May
2012, pp. 639–645.
197
Spectral characterization of selected Compounds:
1-phenyl but-3-en-1-one (table 4 entry 1)3a:83
O
IR (υmax, KBr Pellet in cm- 1): 1701, 1669, 3009 ; 1HNMR
(90MHz, CDCl3/TMS): 7.25-8.4 (ArH,m), 3.89(2H, d),
5.82- 6.09(1H, m), 5.09-5.39(2H, dd); 13 C NMR (22.5MHz,
CDCl3/TMS) δ171.94, 133.77, 130.2, 129.4, 128.41,105.07,
42.28.
1-(2-chloro phenyl) but-3-en-1-one (table4 entry 2) 3b :
O
Cl
IR (υmax, KBr Pellet in cm- 1): 1715,1680, 3071, 776; 1HNMR
(90MHz, CDCl3/TMS) : δ 7.42-7.93 (ArH, m), 3.33 (2H,
d),4.76-5.11 (1H, m), 4.23(2H,dd); 13CNMR(22.5MHz,
CDCl3/TMS): δ 166.64, 132.30, 131.70, 131.38, 130.73,
126.96, 119.67, 37.40
1-(furan-2-yl) but-3-en-1-one (table 4 entry 5) 3e:
O O
IR (υmax, KBr Pellet in cm- 1): 1717, 1648, 3127, 1077;
1HNMR (90MHz, CDCl3/TMS) :δ7.53 - 7.33 & 6.78(3H, m) ,
3.6(2H, d), 6.57-6.55(1H, m), 4.365.22 (2H, dd);
13CNMR(22.5MHz,CDCl3/TMS):δ178.28, 162.32, 147.19,
143.92,119.39,112.21,111.82, 27.67.
1-(5-methyl-3-phenyisoxazol-4-yl) but-3-en-1-one (table 4 entry 6) 3f :
N
O
O
CH3
IR(υmax, KBr Pellet in cm- 1): 1719, 1599, 3108 , 1678, 1058 ;
1HNMR (90MHz, CDCl3 /TMS) : 8.18-8.22 (ArH, m), 3.67
(2H, d), 6.29 (1H, m), 4.96-5.04 (2H, dd), 2.49 (3H, s);
13CNMR (22.5MHz, DMSO / TMS) : 174.9, 162.16,
160.53, 132.88, 131.09, 129.15, 128.38, 126.87, 109.92,
42.30, 12.82.
198
1-(3-(2,6-dichlorophenyl)-5-methylisoxzol-4-yl)but-3-en-1-one (table 4 entry 7) 3g:
N
O
O
ClCl
CH3
IR(υmax, KBr Pellet in cm- 1): 1712, 1637, 3060, 1645, 1069,
717; 1HNMR (90MHz,CDCl3/TMS): 7.78-8.34 (ArH, m),
3.97 (2H, d), 6.48 (1H, m), 4.23-4.54 (2H, dd), 2.57 (3H, s) ;
13CNMR (22.5MHz, CDCl3 /TMS ) : 175.74, 162.12,
158.67, 134.65, 131.97, 128.10, 109.93, 42.29, 12.80.
1, 4-Diphnyl-but-- 3- en-1 one (table 4 entry 11)4a 84:
O
IR (υmax, KBr Pellet in cm- 1): 1450,1598,1679,3062 ;
1HNMR (90MHz, CDCl3/TMS): 3.89(2H, br S), 5.82-
6.09(1H, m), 5.09-5.39(1H, dd), 7.25-8.4(ArH,m); 13 C
NMR (22.5MHz, CDCl3/TMS): δ171.94, 133.77,
130.2,129.4, 128.41,105.07, 42.28
1-(2-Chloro phenyl)-4-phenyl-but-3-en-1-one (table 4 entry 12)4b:
O
Cl
IR (υmax, CHCl3 in cm- 1): 725,1249,1443,1593,1724,3020 ;
1HNMR (90MHz, CDCl3/TMS): 3.53(2H, br S), 6.33-
6.53(1H, m), 5.11(1H, d/d) ,7.32-7.83(ArH,m); 13 C NMR
(22.5MHz, CDCl3/TMS): 165.00,132.98,132.87, 132.01,
130.84, 130.51, 130.00, 129.4, 128.00, 127.13, 126.18,
125.54, 44.87.
1-Furan-2yl-4-phenyl-but-3en-1-one (table 4 entry 13)4c:
OO
IR (υmax, CHCl3 in cm- 1): 1014, 1116, 1473, 1581, 1701,
2877, 3016 ; 1HNMR (90MHz, CDCl3/TMS): 3.85(2H,br
S) , 6.08 (1H,m), 6.26-6.41(1H,dd),6.53-6.71(3H,m),7.31-
7.67(ArH, m); 13 C NMR (22.5 MHz, CDCl3 /TMS) :
160.34,146.09, 144.07, 135.41,133.51,1238.08, 126.16,
124.38, 118.91, 111.16, 44.87
199
2-Methyl-6-phenyl-hex-5-en-3-one (table 4 entry 14)4d:
O
H3C
H3C
IR (υmax, CHCl3 in cm- 1): 1438,1593,1724,3020 ; 1HNMR
(90MHz, CDCl3/TMS): 1.13-1.21 (6H,d),2.13-2.55 (1H,m),
3.85(2H,br S), 6.16 (1H, m), 6.26-6.41(1H,dd), 6.26-6.54
(1H,dd), 6.54-6.71(ArH, m), 7.30-7.38(ArH, m); 13CNMR
(22.5MHz, CDCl3/TMS) : 181.64, 135.63,133.81, 128.33,
127.94, 126.39, 125.00, 124.3, 45.07, 31.98, 23.18, 21.75,
18.47.
200
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