Robert Knowles PCET - RenaudResearchGrouprenaud.dcb.unibe.ch/topic-review/topic-review-2016/tr...2016/06/30 · 9 Concerted PCET/Effective Bond Strengths H. Yayla, R. Knowles, Synlett

Topic Review

Chemistry of Robert Knowles - PCET

Samuel RiederDCBUniversität Bern

30th June 2016

2

Overview

- Robert R. Knowles

- Proton Coupled Electron Transfer (PCET)

- Ketyl-Olefin Cyclization

- Conjugate Amination

- Olefin Carboamination

- Olefin Hydroamination

3

Robert R. Knowles

2003 B.S. in Chemistry, College of William andMary, Williamsburg, Virginia

2008 Ph.D. in Chemistry, David MacMillan, Caltech, Pasadena, California

08-11 NIH Postdoc, Eric Jacobsen, Harvard University, Cambridge, Massachusetts

11-pres. Assistant Professor, Princeton University, Princeton, New Jersey

Research Interest- Radical- and Photochemistry- Exploring the synthetic application of proton-coupled electron transfer (PCET)

http://chemists.princeton.edu/knowles/

4

Proton-Coupled Electron Transfer (PCET)Introduction

J. M. Mayer, Annu. Rev. Phys. Chem. 2004, 55, 363–390J. J. Warren, T. A. Tronic, J. M. Mayer, Chem. Rev. 2010, 110, 6961–7001.

- Electron transfer (ET) and Proton transfer (PT) most fundamental processes in chemistry

- PCET: Both processes in one concerted step- Concerted: absence of intermediate but does not imply synchronous

transfer- “Simplest“ PCET reaction is hydrogen-atom transfer (HAT)

X H YHAT

+ X YH+

- Former Definition: PCET concerted e–/H+ transfer ≠ HAT

- Distinction between PCET and ET/PT or PT/ET difficult to make

X H YPCET

+ XB + B H Y+ +

H+

e–

5

Proton-Coupled Electron Transfer (PCET)Introduction; Mechanism

- Kinetic advantage of PCET- Thermochemical bias- Circumvention of high energy

intermediates formed in elementary ET or PT

- Concerted vs stepwise e–/H+ Transfer

J. J. Warren, T. A. Tronic, J. M. Mayer, Chem. Rev. 2010, 110, 6961–7001S. Y. Reece, D. G. Nocera, Annu. Rev. Biochem. 2009, 78, 673–699.

X H Y+

X Y+ X YH H+

ET

ET

X H Y+

PTPTPCET

6

Proton-Coupled Electron Transfer (PCET)Introduction; Examples

S. Fukuzumi, K. Ishikawa, K. Hironaka, T. Tanaka, J. Chem. Soc. Perkin Trans. II 1987, 751–760. V. W. Manner, A. G. Dipasquale, J. M. Mayer, J. Am. Chem. Soc. 2008, 130, 7210–7211

- Reduction of dioxygen to water

O2 4e– 4H+ 2H2O++

- TEMPOH and Ru(III) (Ru and COOH distance ~ 11 Å)

FeIIMe

Me

O

O

2H+ FeIIIMe

Me

OH

OH

++ +2 2

- Reduction of quinone with ferrocene and HClO4

RuIIIN

NN N

O

OO

O

O

O NOH

RuIIN

NN N

O

OO

O

OH

ONO

+ +

7

Proton-Coupled Electron Transfer (PCET)Different Pathways; Thermochemistry of PCET Reagent

S. Y. Reece, D. G. Nocera, Annu. Rev. Biochem. 2009, 78, 673–699

- Unidirectional and bidirectional PCET

- In nature

A

X

HB

protontransfer

electrontransfer

PCETA

X

HB

- Photosystem II (H2O à O2), alcohol dehydrogenase, ribonucleotide reductase, cytochorome P450

8

Proton-Coupled Electron Transfer (PCET)Thermochemistry of PCET Reagent; BDFE (X–H)

- Thermochemical square for PCET reagent

X–

X

X H

X H

BDFE

pKa(XH)

pKa(XH)

E0(X–/X•)E0(XH/XH)

- BDFE (bond dissociation free energy) ≠ BDE (bond dissociation enthalpy)

- Three independant parameters- ∆pKa upon oxidation = ∆E0 upon

deprotonation (Hess‘ law)

∆𝐺°$% =– 𝑅𝑇𝑙𝑛 𝐾. =– 1.37𝑘𝑐𝑎𝑙𝑚𝑜𝑙–8 𝑝𝐾.

∆𝐺°:% =– 𝐹𝐸° =– 23.06𝑘𝑐𝑎𝑙𝑚𝑜𝑙–8𝑉–8 𝐸°

𝑩𝑫𝑭𝑬𝒔𝒐𝒍 𝑿–𝑯 = 𝟏.𝟑𝟕𝒑𝑲𝒂 + 𝟐𝟑.𝟎𝟔𝑬° + 𝑪𝑮,𝒔𝒐𝒍

- pKa and E° from adjacent sides of the square scheme

S. Y. Reece, D. G. Nocera, Annu. Rev. Biochem. 2009, 78, 673–699F. G. Bordwell, J. P. Cheng, J. A. Harrelson, J. Am. Chem. Soc. 1988, 110, 1229–1231.

9

Concerted PCET/Effective Bond Strengths

H. Yayla, R. Knowles, Synlett 2014, 25, 2819–2826.

- Feasibility of HAT process is function of BDFE differential between two bonds undergoing exchange

- Addition of H• to organic π-systems à nascent bond very weak due to destabilisation by adjacent unpaired electron

Me Me

O

Me Me

O HO–H BDFE

~ 16 kcal/molLnMm H LnMm–1+ +

LnMm HC–H BDFE

~ 33 kcal/mol HLnMm–1+ +

LnMm HN–H BDFE

~ 28 kcal/molLnMm–1+ +

Me H

N Et

Me H

N EtH

- Requires HAT from comparably weak bond in H-atom donor

10

Concerted PCET/Effective Bond Strengths”Design” of a H-atom donor

H. Yayla, R. Knowles, Synlett 2014, 25, 2819–2826.

- To weaken scissile X–H bond in H-atom donor- 1. Increase Brønsted acidity- 2. Conjugate base more reducing- 3. Combination

- Making X–H more acidic à loss of reducing ability (Interdependence)- These compensatory effects confine H-atom donor classes to narrow

range of BDFE values

- Multisite PCET reactions (no bond homolysis for “HAT”)- Independent variation- Broader Range of BDFE values- Enable HAT reactivity of wide range of common organic functional groups

11

Catalytic Ketyl-Olefin Cyclization (JACS)Ru-photocatalyst, (RO)2PO2H

K. T. Tarantino, P. Liu, R. R. Knowles, J. Am. Chem. Soc. 2013, 135, 10022–10025.

Ar

OCO2Me

redox catalystBrønsted acid catalyst

stoichiometric reductant OO

H

Ar

Ar

OCO2Me

H

- Idea; Why PCET?- Many organic functionalities exhibit large ∆pKa upon 1e– oxidation- Favourable PT enabling redox reagents with potentials far less energetic- Concerted activation à attractive for photoredox catalysis

- Many X• (from X–H) still inaccessible (high BDFE)- Potential unattainable or ET transfer event too slow for catalyst*

12

Catalytic Ketyl-Olefin CyclizationResearch Design

- Typical ketone almost inert to all but the most strongly reducing photocatalysts (E1/2red = –2.48 V vs Fc for acetophenone)

- Weakly basic à small concentration of oxocarbenium ions- Acid/reductant pair thermodynamically equivalent to BDFE to ketyl O–H

Ph

O

Me

XH

Mn

PT

ET

Keq (PCET)Ph

O

Me

HX

Mn+1

O–H BDFE ~ 26 kcal/mol

Mn X H Mn X H

Mn+1 X– H•"BDFE"

pKa

E° E°C

“𝐵𝐷𝐹𝐸“ = 1.37𝑝𝐾.(𝐻𝑋)+ 23.06𝐸°(𝑀_) + 𝐶a,bcd

- O–H BDFE calculated with CBS-QB3- ‘BDFE’(pair) ~ O–H(ketyl) à reaction kinetically feasible?


13

Catalytic Ketyl-Olefin CyclizationCatalytic Cycle

H XRuI(bpy)2

RuII(bpy)2

HEH

HEH+•ET

hν

H XRuI(bpy)2

O PhCO2Me

HO PhCO2Me X–

RuII(bpy)2

OHPhMeO2C

RuII(bpy)2

X–

NH

CO2EtEtO2C

MeMe

H H

NH

CO2EtEtO2C

MeMe

H

RuII(bpy)2

X–

OHPhMeO2C

N

CO2EtEtO2C

MeMeH RuI(bpy)2

X–

N

CO2EtEtO2C

MeMe

hν ET C–C bondformation

PT PCET

HAT

HEH


14

Catalytic Ketyl-Olefin CyclizationCondition Optimization; Catalyst Pairs

Ph

OCO2Me

redox cat. (2 mol%)acid cat. (5 mol%)HEH (1.5 equiv.)

THF [0.05], visible hν, rt, 4 h OO

H

PhHO

H

Ph

MeO2C+

1 2 3


15

Catalytic Ketyl-Olefin CyclizationScope

- Selectivity improved when BT instead of HEH- C–C bond formation may be reversible- Diastereoselctivity determined by rates of HAT step

NH

SPh

BT

O

O

HPh

73% (11:1)X

O

O

HPh

X= O, 87% (4.8:1)X= NTs, 80% (3.4:1)

O

O

O

H

Z= OMe, 78% (12:1)Z= Me, 86% (6:1)

Z

O

O

H

O

O

H

68%

MeO

82% (16:1)

Me

n= 1, 96% (2:1)n= 2, 78% (1.2:1)

n

Ph


16

Catalytic Ketyl-Olefin CyclizationMechanistic Investigation

- Fluorescence quenching techniques (acetophenone (AP))- Stern-Volmer Analysis (AP alone does not quench Ir*(ppy)3)- Addition of (PhO)2PO2H à decrease of fluorescence- (PhO)2PO2H alone does not quench Ir*(ppy)3

- Quenching: First order dependance on each component- KIE 1.22 ± 0.02 (PhO)2PO2H/(PhO)2PO2D➔ Preclusion of direct e–-transfer in quenching (ET/PT)

- Rate law consistent with either stepwise (PT/ET) or concerted mechanism- Discount former à large pKa difference between phosphoric acid (~ 13)

and protonated ketone (~ –0.1)- KPT > 106 too slow to be competitive with decay of Ir(III)* (5.3 x 105 s–1)- Discount PT/ET à concerted (–1.9 kcal/mol)

K. T. Tarantino, P. Liu, R. R. Knowles, J. Am. Chem. Soc. 2013, 135, 10022–10025.H. Yayla, R. Knowles, Synlett 2014, 25, 2819–2826.

17

Asymmetric Aza-Pinacol Cyclization (JACS)Synthesis of Vicinal Amino Alcohols

L. J. Rono, H. G. Yay la, D. Y. Wang, M. F. Armstrong, R. R. Knowles, J. Am. Chem. Soc. 2013, 135, 17735–17738.

Ar

ON

photoredox catalystchiral acid catalyst

stoichiometric reductantR

OHAr HN R

HNAr

O

R

H O PO

RO ORPCET

- Proton in H-bond expected to shift from acid to ketyl during course of ET- H-bond interface remains intact- Chiral phosphate should render reaction enantioselctive

Ph

ON

Ir(ppy)2(dtbpy)PF6 (5 mol%)acid cat. (10 mol%)HEH (1.5 equiv.)

1,4-dioxane [0.05], rt 3 hNMe2

OHAr HN NMe2

18

Asymmetric Aza-Pinacol CyclizationCatalytic Cycle


H OP(O)(OR)2IrII(ppy)2(dtbpy)

NH

CO2EtEtO2C

MeMe

H H

NH

CO2EtEtO2C

MeMe

H

N

CO2EtEtO2C

MeMeH

N

CO2EtEtO2C

MeMe

hν ET C–C bondformation

PT PCET

HAT

HEH

HN

PhO

R

H O PO

RO OR

HN

PhO

NMe2

IrIII(ppy)2(dtbpy)

HN

PhO

NMe2

H O PO

RO OR

IrIII(ppy)2(dtbpy)

HNH

PhO

NMe2

H

–OP(O)(OR)2

IrIII(ppy)2(dtbpy)

IrII(ppy)2(dtbpy)

–OP(O)(OR)2

HEH

HEH+•ET

hν

IrII(ppy)2(dtbpy)

IrIII(ppy)2(dtbpy)

19

Asymmetric Aza-Pinacol CyclizationOptimizing Conditions


- No trans diastereoisomerobserved in any case

- In case of no acid, a 3:1 mixture was obtained (cis:trans)

- In absence of photocatalystno starting material was consumed

20

Asymmetric Aza-Pinacol CyclizationScope


- Significant structural and eletcronical variations of Ar well tolerated- ortho-, meta-, and para-substitution, heterocycles

NHNMe2HOZ

Z= H; 83% (93% ee)Z= Me; 81% (95% ee)

Z= OMe; 86% (94% ee)Z= Br; 77% (95% ee)

Z= CF3; 58% (90% ee)

NHNMe2HOZ

YZ= H; Y= Me; 63% (94% ee)Z= Me; Y= H; 78% (90% ee)

NHNMe2HO

MeMe

78% (90% ee)O

NHNMe2HO

85% (83% ee)

NHNMe2HO

96% (94% ee)

O

ONHNMe2HO

53% (82% ee)

O

NHNMe2HO

69% (85% ee)

S

Br NHNMe2HO

71% (77% ee)

21

Asymmetric Aza-Pinacol CyclizationMechanistic Investigation


- KIE = 1, with HEH and 4,4-d2-HEH (independent experiments)➔ inconsistent with rate-limiting HAT➔ C–C bond formation is turnover-limiting and enantioselectivity-determining- Linear relationship between ee (catalyst) and ee (product)➔ Only one molecule of acid in key C–C bond forming step- Position of proton (DFT Evaluation)

22

Conjugate Amination (JACS)Soft Homolysis of Strong N–H bonds

K. T. Tarantino, D. C. Miller, T. A. Callon, R. R. Knowles, J. Am. Chem. Soc. 2015, 137, 6440–6443.

- Coordination of redox-active metal-centres decreases ligand homolyticbond strengths

N

P(t-Bu)2

P(t-Bu)2

CoI

H

Cl

BDFEC–H 50 kcal/mol

TiIIICl

OH

H

BDFEO–H 49 kcal/mol

- Complexation for bond weakening of strong X–H bond for “soft” HAT

R1N

RO

X

OR2

H

Mn

ET

PT

PCET

R1N

RO

X

OR2

Mn

H

23

Conjugate AminationModel reaction

K. T. Tarantino, D. C. Miller, T. A. Callon, R. R. Knowles, J. Am. Chem. Soc. 2015, 137, 6440–6443K.-W. Huang, R. M. Waymouth, J. Am. Chem. Soc. 2002, 124, 8200–8201.

N

O

X

Cp*2Ti(III)Cl (1 mol%)TEMPO (1 mol%)

CO2MeN

XO

H

Ar CO2Me

Ar H

N

O

XAr CO2Me

Ti(IV)(Cp*)2Cl

TEMPO H

- Direct formation of closed-shell organometallic intermediate (no radical)- Metalated Nu under neutral conditions- Combinations à Pair cooperative activation, but no reaction- TEMPO as model H-abstractor (handling, E1/2red = –1.95 V vs Fc)- Cp2Ti(III)Cl à bond weakening ability known- Reaction together à strong complex (not with Cp*2Ti(III)Cl)

24

Conjugate AminationCatalytic Cycle

K. T. Tarantino, D. C. Miller, T. A. Callon, R. R. Knowles, J. Am. Chem. Soc. 2015, 137, 6440–6443

TEMPO

PCET

ET coordination

Cp*2Ti(III)Cl NH

O

OPh CO2Me

NH

O

OPh CO2Me

Ti(III)Cl(Cp*)2

TEMPO

N

O

OPh CO2Me

Ti(IV)Cl(Cp*)2

TEMPO–H

C–N bondformation

MeO

O Ti(IV)Cl(Cp*)2

ON

O

Ph

PT

TEMPO–H

MeO

O

ON

O

Ph

Ti(IV)Cl(Cp*)2

TEMPO–

25

Conjugate AminationOptimization; Scope


- Unsbustituted and nonosubstituted titanocenes cabable of forming strong complexes with TEMPO were not catalytically active à Cp*2Ti(III)Cl

- Good results in MeCN or DMF, poor in aromatic, etheral or chlorinated solvents

- Other nitroxyl radical suitable as well (AZADO)

X

NOCO2Me

Ph

X= CH2; 87%X= O; 94%

X

NOC(O)CH3

Ph

X= O; 95%X= S; 69%

X= NH; 96%

O

N 22

11

O33

CO2Me

Ph

1-Me; 92% (trans, dr 10:1)2-Me; 88%

3-Me; 98% (2,3-anti dr >20:1)

X

NOCO2Me

Ar

X= O; Ar= PMP; 96%X= N; Ar= Ph-4-CF3; 97%X= O; Ar= Ph-3-Cl; 96%

X= O; Ar= 3-benzodioxol; 95%

NO CO2Me

Ar

86%

NO

Ph

O

O

94%

26

Conjugate AminationCalculations


27

Conjugate AminationMechanistic Investigation


- First order dependancies on eachcomponent (carbamate, TEMPO, and Ti(III))

- KIE of 7±1 of N–H and N–D (individual reactions)

➔ Rate limiting N–H abstraction byTEMPO

28

Alkene Carboamination (JACS)Oxidative PCET

G. J. Choi, R. R. Knowles, J. Am. Chem. Soc. 2015, 137, 9226–9229.

- Generation of amidyl radical with non-coordinating redox active metal

N

OIr(III) redox cat.cat. phosphate baseolefin acceptor

R2NO

H

Ar R2

ArR1 R3

R1visible hν

- Catalyst pair unable to react with each other or the substrate individually

N

OAr R2

R1PCET

NO

R

ArMn

ET

PCETH B NO

R

ArMn–1 BH

PT

29

Alkene CarboaminationCatalytic Cycle


Mn

ET C–N bondformation

PT PCET

B

hνN

O

H

Ph Me

Me

N

OPh Me

MeBH

Mn–1

R2NO

Ph

R1

BH

Mn–1

CO2Me

R2NO

Ph

R1

CO2MeBH

Mn–1

R2NO

Ph

R1

CO2MeMn

BH

R2NO

Ph

R1

CO2Me

H

C–C bondformation

30

Alkene CarboaminationOptimization


photocatalyst (3 mol%)Bønsted base (25 mol%)methyl acrylate (3.0 equiv.)

CH2Cl2 [0.4], blue LEDs, rt, 12 h

31

Alkene CarboaminationScope (Selection); Olefin-, Aryl-, Acceptor-Variations


XN

O Ph

CO2Me

X= CH2; 95%X= O; 87%

X= NMe; 63%X= S; 72%

O

NO

PhMe

CO2Me

82% (dr 6:1)

O

O

O

NO

O

Ph

CO2Me

63% (dr >20:1)

XN

O

CO2Me

X= OMe; 78%X= CN; 94%X= F; 86%

X= OCF3; 70%

X

XN

O Ph

EWG

O

H

OCN N

94% 50% 78% 76%

X

NOPh

CO2Me

80%

32

Alkene CarboaminationMechanistic Investigation

G. J. Choi, R. R. Knowles, J. Am. Chem. Soc. 2015, 137, 9226–9229L. Q. Nguyen, R. R. Knowles, ACS Catalysis 2016, 6, 2894–2903.

- Luminescence quenching à Stern-Volmer analysis, N-phenyl-acetamide(NPA) does not quench Ir(III)*

- Solution containing NPA and phosphate à decrease emission efficiency- Rate law (quenching) à first order dependence (both components)- KIE = 1.15 ± 0.04 (independent experiments, N–H vs N–D)➔ Discard ET/PT➔ Either PT/ET or PCET- Stepwise pathway ruled out (thermodynamics à pKa difference (~ 20))➔ Not kinetically competitive with luminescent decay of Ir(III)* (τ = 2.3 µs)➔ Rate law and KIE consistent with PCET

33

Alkene Hydroamination (JACS)PCET Activation of Amide

D. C. Miller, G . J. Choi, H. S. Orbe, R. R. Knowles, J. Am. Chem. Soc. 2015, 137, 13492–13495.

- Current methods for amidyl-based hydroamination à

Prefunctionalization, stoichiometric strong oxidant- Redox-neutral conditions have potential to increase value/atom

economy of these methods

N

OIr(III) redox cat.cat. phosphate baseH-atom donor cat.

R2NO

H

Ar R2

Ar HR1

R1visible hν

N

OAr R2

R1PCET

34

Alkene HydroaminationReaction Design


- Combination redox cat/phosphate base from carboamination➔ Selective cleavage of N-H bond in presence of H-atom donor

Ir(III)+

(BuO)2PO2 NH

OPh

N

OPh

Ir(II)(BuO)2PO2H

N

OPh

N

O

Ph

H Ir(II)(BuO)2PO2H

Ir(II)(BuO)2PO2H R R H

PCET

C–N bondformationHAT

ET/PT

H-atomdonorcatalyst

35

Alkene HydroaminationOptimization; H-Atom Donor


N

OIr(dF(CF3)ppy)2(bpy)PF6 (2 mol%)(BuO)2PO2NBu4 (20 mol%)H-atom donor (10 mol%) N

O

H

PhPh

H

CH2Cl2 [0.3], blue LEDs, rt 20 h

R R

RR

- Reduction à allylic position- Thiophenol most efficient- Thiols known for multisite

PCET activation- N–H BDFE ~ 99 kcal/mol vs S–

H BDFE ~ 79 kcal/mol- Raises questions about origin

of selectivity

36

Alkene HydroaminationScope


- Accomodation of a variety of di-, tri-, and tetrasubstituted olefins- Styrenyl acceptor (30 mol% thiophenol)- Steric hindrance adjacent to C–N bond formation tolerated- Carbamates, thiocarbamtes- Reactions largely insensitive to olefin geometry- Synthesis of a number of bicyclic systems- Unprotected O–H well tolerated- Both, electron-rich and –deficient anilides cyclized smoothly- Reaction proved insensitive to ortho substitution- Method currently does not accommodate intermolecular coupling or

formation of larger rings with high efficiency➔ Back electron transfer from amidyl radical is kinetically favored

37

Alkene HydroaminationScope


NOPh

HMe

MeMe

89%

N

OO

Ph H

81%

PhNO

Ph

H

85%

N

XO

Ph H

X= O; 89%X= NMe; 90%

X= S; 73%

N

OO

Ph H

88% (dr >20:1)

N

OO

Ph

H

86%

N

OO

Ph H

92% (dr >20:1)

Me

Me

MeOH

NO

Ph

H

68% (dr >20:1)

N

O

HMe

para-Me; 93%meta-Me; 88%ortho-Me; 87%

N

O

H

X

X= OMe; 87%X= CN; 80%X= F; 88%

X= OCF3; 91%

N

O

H

82%

NO

O

HN

88%

N

O

H

O

PhCO2Me

TBSOMe

OC

O

87% (dr 5:1)

38

Alkene HydroaminationMechanistic Investigation


- Two substrates for PCET (∆∆G° ~ 20 kcal) with driving force for thiol- Luminescence quenching experiments à thiol and acetanilide (AA) do not

affect emission intensity of Ir(III)*- Solution with base and either thiol or AA à efficient quenching- Fixed [thiol] and [base], variation of AA à first order dependence on AA- Fixed [AA] and [base], variation of thiolà no additional quenching above

background➔ PCET of amide not only feasible but dominant- DFT calculations: amide-phosphate bond more stable by 5.2 kcal/mol than

thiophenol-phosphate complex➔ Significantly higher concentration of amide-phosphate complex in

solution

39

Conclusion

- Novel protocol for catalytic ketyl radical chemistry- First catalytic protocol for enatioselective aza-pinacol cyclizations- Catalyst identification using Mayers’s effectice bond-strength formalism

“BDFE“ = 1.37pKk(HX) + 23.06E°(Mo) + Cq,rst- Conjugate amination protocol catalyzed by Cp*2Ti(III)Cl and TEMPO- Novel PCET-based protocol for alkene carboamination- Direct homolytic activation of strong N–H bonds- Alkene hydroamination protocol mediated by three distinct catalysts –

photocatalyst, Brønsted base, thiol H-atom donor- Multisite PCET activation of strong amide N–H bond in presence of a much

weaker S–H bond

Thank you for your attention

40

Back-up SlideFluorescence Quenching Techniques

- Different methods- Excited state reactions - Complex formation- Energy transfer - Collisional quenching

- Stern-Volmer Analysis- Allows to explore the kinetics of a photophysical intermolecular

deactivation process

Q AA* Q*+ + Q AA* Q+ +

𝐼vw

𝐼v= 1 + 𝑘x𝜏w[𝑄]

If0: intensity/rate without quencher QIf: intensity/rate with quencher Qkq: Quencher rate coefficientτ0: lifetime of emissive excited state of A[Q]: concentration of quencher Q

41

Back-up SlideCalculation; Constant C

L. Q. Nguyen, R. R. Knowles, ACS Catalysis 2016, 6, 2894–2903.

42

Back-up SlideHess’ Law; Calculation

- Hess's law states that the change of enthalpy in a chemical reaction (i.e. the heat of reaction at constant pressure) is independent of the pathway between the initial and final states

- BDE vs BDFE

∆𝐻 = ∆𝑈 + ∆𝑃𝑉H: EnthaplyU: EnergyP: PressureV: Volume

- ∆H = ∆U if ∆P = 0

- Discussions: ∆U instead of ∆H

43

Back-up SlideCalculation

F. G. Bordwell, J. P. Cheng, J. A. Harrelson, J. Am. Chem. Soc. 1988, 110, 1229–1231.

44

Back-up SlideCurrent Methods for Amidyl-Based Hydroamination

L. Q. Nguyen, R. R. Knowles, ACS Catalysis 2016, 6, 2894–2903.

45

Back-up SlideHAT pairs

D. C. Miller, K. T. Tarantino, R. R. Knowles, Top. Curr. Chem. (Z) 2016, 374, 30.

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Robert Knowles PCET - RenaudResearchGrouprenaud.dcb.unibe.ch/topic-review/topic-review-2016/tr...2016/06/30 · 9 Concerted PCET/Effective Bond Strengths H. Yayla, R. Knowles, Synlett