P. Molina, A. Tarraga, M. J. del Bafio, A. Espinosa 223

Notiz/Note

Unexpected Triphenylphosphane-Promoted Conversion of 2-Azido-3-vinyl-1,4- naphthoquinones into 2-Amino-3-acyl-l,4-naphthoquinones Pedro Mobax, Albert0 Thrraga, Maria Jod del Baiio, and Arturo Espinosa

Departamento de Quimica Organica, Facultad de Quimica, Universidad de Murcia, Campus de Espinardo, E-30071 Murcia, Spain

Received September 9, 1993

Key Words: 1 ,CNaphthoquinones I Phosphanes

An unusual behavior of several 2-azido-3-vinyl-l,4-naphtho- quinones 1 towards triphenylphosphane leading both to chain oxidation is described.

azido group reduction and unsaturated carbon-carbon side

Recently, we have reported['] that iminophosphoranes derived from anilines, bearing an unsaturated chain in the ortho position, are valuable building blocks for the preparation of a wide variety of a-carbolines and quinindolines. As a further extension of this work, it was of interest to prepare iminophosphoranes of type 2, in which the benzene ring has been replaced by a naphthoquinone one. To this end, a number of 2-azido-3-vinyl-1 ,4-naphthoquinones 1 were prepared by a previously described procedure[2].

Although the reaction of alkyl and aryl azides with tertiary phos- phanes (Staudinger reaction) has been widely used in the prep- aration of iminopho~phoranes[~], the reaction of 2-azido- 1 ,Cnaph- thoquinones with trivalent phosphorus compounds has not been studied to the same extent. It has only been described[4] that 2,3- bis(azid0)- 1 ,Cnaphthoquinone reacts with triphenylphosphane to give a mixture of the corresponding bis(imino)phosphorane and the iminophosphorane derived from 2-aminonaphtho[2,3-dtria- zole-4,9-dione. The formation of the latter compound is explained by the initial addition of the phosphane to one of the azido groups producing a phosphazene which promotes the decomposition of the second azido group with concomitant formation of the triazole ring. A related mechanism has been proposed for the reaction of aryl azides bearing an unsaturated functionality in the ortho pos- ition (e.g. o-azidobenzaldimines and o-azidobenzaldehyde) with tertiary phosphanes to give iminophosphoranes derived from 2- amino-3-acylamino-2H-indazole instead of the expected arylimino- phosphorane~[~J.

When equimolar amounts of triphenylphosphane were added to a solution of azide l a in CH2C12 cooled to -3O"C, a deep blue to violet color developed and after the reaction mixture had been al- lowed to warm up to room temp., the 2-amino-3-acyl- l ,Cnaphtho- quinone 3a was isolated in moderate yield after column chromatog- raphy as the only reaction product, instead of the expected imino- phosphorane 2. Reaction of the related 2-azido- 1,4-naphthoqui- nones lb-d also resulted in the formation of the 1,4- naphthoquinone derivatives 3b-d, and no other identifiable prod- uct could be detected under extremely dry chromatographic con- ditions. Similar results were also achieved by using other P(II1) reagents, e.g. tributyl- or tri(o-tolyl)phosphane, triethyl phosphite

py N=PPh3 2

I

1

or ethyldiphenylphosphane, and no reaction was observed upon treatment of l c with 1,2,S-triphenylphosphole in refluxing dry CH2C12 for 3 h. However, when the reaction was carried out at room temp., a complex mixture was obtained in which the corre- sponding 2-amino-3-acyl-1 ,Cnaphthoquinone 3 was not detected.

The structures 3 were established on the basis of their microana- lytical and spectral data. In the 'H-NMR spectra the methylene protons in the a position to the carbonyl group appear near 6 = 3, whereas in the I3C-NMR spectra the corresponding carbon atoms resonate in the range 6 = 37.71-45.88. Mass spectra show the expected molecular ion peaks in moderate to high intensity.

It is worth noting that this simple reaction, which overall involves loss of nitrogen and hydration, affects both substituents on the quinone ring: the azido function is reduced to the amino group and the unsaturated carbon-carbon side chain is converted into an acyl group. No similar transformations have been previously re- ported to the best of our knowledge.

We gratefully acknowledge the financial support of the Direccion General de Investigacidn Cientifica y Tkcnica (project number PB89-0436).

Liebigs Ann. Chem. 1994,223-224 0 VCH Verlagsgesellschaft mbH, D-69451 Weinheim, 1994 0170-2041/94/0202-0223 $10.00+.25/0

224 P. Molina, A. Tirraga, M. J. del Baiio, A. Espinosa

Experimental Melting points (not corrected): Kofler hot-stage apparatus. -

Elemental analyses: Eager 200 instrument. - IR: Nicolet FT-5DX spectrophotometer; Nujol emulsions in NaCl plates. - 'H and 13C NMR: Varian Unity 300; 'H (299.95 MHz) and I3C NMR (75.43 MHz) in 6 values relative to internal TMS; CDC13 solutions; signal assignment by DEPT-135 spectra, and for compound 3c I3C gated decoupled, COSY-45 and 'H-I3C 2D heteronuclear correlation experiments were also carried out. - MS: Hewlett-Packard 5993 C spectrometer; by electron impact at an ionizing voltage of 70 eV. - Column chromatography: Silica gel 60 (Merck) as stationary phase; columns of 4.5 cm diameter and 70 cm height.

General Procedure: A solution of triphenylphosphane (0.35 g, 1.33 mmol) in CH2ClZ (20 ml) was added to a cooled solution (-30°C) of the corresponding azidonaphthoquinone 1 (1.33 mmol) in the same solvent (20 ml) under argon. After being stirred for 6 h at this temp., the reaction mixture was allowed to warm up to room temp. and then stirred for 12 h. The solvent was evaporated in vacuo and the residue subjected to chromatography (eluant: CH2Cl2/AcOEt, 9: 1) to give 3, which was further purified for ana- lytical purposes by recrystallization from CH2C12/hexane.

2-Amino-3-propionyl-I,4-naphthoquinone (3a) (0.137 g; 45%), ob- tained as brown prisms with m.p. 137-138°C. - IR: 5 = 3360 (NH), 3258 (NH), 1688 (CO), 1622, 1595, 1578, 1308, 1291, 1184, 737, 727, 706, 690 cm-'. - 'H NMR: 6 = 10.62 (br. s, 2H, NHz), 8.16 (dd, 3J = 7.5 Hz, 4J = 1.1 Hz, l H , 5-H), 8.01 (dd, 3J = 7.7 Hz, 4J = 1.1 Hz, lH , 8-H), 7.76 (td, 3J = 7.5 Hz, 4J = 1.1 Hz, 1 H, 6-H), 7.60 (td, 3J = 7.6 Hz, 4J = 1.1 Hz, 1 H, 7-H), 3.14 (q, 3J = 7.2 Hz, 2H, CHZCH,), 1.10 (t, 3J = 7.2 Hz, 3H, CH2CH3). - I3C NMR: 6 = 205.47 (s, COCHZ), 181.33 (s , C-l), 181.05 (s, C-4), 152.62 (s, C-2), 136.04 (d, C-6), 134.09 (s, C-4a), 132.46 (d, C-7), 129.61 (s, C-Sa), 127.25 (d, C-5), 126.25 (d, C-8), 108.67 (s, C-3), 37.77 (t, CH2CH3), 8.60 (q, CHzCH3). - MS: m/z (%) = 229 (23) [M+], 200 (30), 172 (16), 149 (31), 105 (ll), 68 (14), 58 (loo), 57 (34). - Cl3HlLNO3 (229.2): calcd. C 68.11, H 4.84, N 6.11; found C 67.96, H 4.65, N 5.94.

2-Amino-3-pentanoyl-l,4-naphthoquinone (3b) (0.165 g; 48%), ob- tained as brown-orange prisms with m.p. 85-86°C. - Rf = 0.46

(NH), 1688 (CO), 1621, 1592, 1559, 1376, 1310, 1289, 1181, 1169, 874,791,732,699 cm-'. - 'H NMR: 6 = 10.62 (br. s, 2H, NH2), 8.14 (dd, 3J = 7.8 Hz, 4J = 1.1 Hz, 1 H, 5-H), 7.99 (dd, 3J = 7.6

lH , 6-H), 7.58 (td, 3J = 7.5 Hz, 4J = 1.1 Hz, lH , 7-H), 3.09 (9, 3J = 7.5 Hz, 2H, CHzCH2CHzCH3), 1.57 (quint, 3J = 7.5 Hz, 2H, CHzCH2CH2CH3), 1.33 (sext, 3J = 7.5 Hz, 2H,

(CHzClz), 0.80 [CHZCIz/AcOEt (9:1)]. - IR: F = 3330 (NH), 3217

Hz, 4J = 1.3 Hz, lH , 8-H), 7.74 (td, 3J = 7.6 Hz, 4J = 1.3 Hz,

CH&HZCHzCH3), 0.87 (t, 3J = 7.4 Hz, 3H, CH3). - I3C NMR: 6 = 205.12 (s, COCHz), 181.41 (s, C-l), 181.03 (s, C-4), 152.56 (s, C-2), 136.05 (d, C-6), 134.14 (s, C-4a), 132.46 (d, C-7), 129.67 (s, C-Sa), 127.28 (d, C-5), 126.26 (d, C-8), 108.87 (s, C-3), 44.27

(t, CHZCHZCHZCH~), 26.84 (t, CHZCH2CHzCH3), 22.66 (t, CHzCH2CHzCH3), 14.11 (9, CH3). - MS: rnlz (%) = 257 (84) [M+], 228 (98), 215 (34), 200 (loo), 172 (40), 149 (9 , 105 (26), 85 (3), 68 (22), 57 (9). - Cl5HI5NO3 (257.3): calcd. C 70.02, H 5.88, N 5.44, found C 69.86, H 5.62, N 4.69.

2-Amino-3- (3-phenylpropionyl)-1,4-naphthoquinone (3c) (0.243 g; 6O%), obtained as yellow needles with m.p. 155-156°C. - Rf =

3217 (NH), 1681 (CO), 1647, 1627, 1579, 1335, 1310, 1291, 1183, 1159, 1017, 991, 788, 734, 724, 700 cm-'. - 'H NMR: 6 = 10.65 (br. s, 2H, NH2), 8.22 (dd, 3J = 7.7 Hz, 4J = 1.3 Hz, IH, 5-H), 8.08 (dd, 3J = 7.5 Hz, 4J = 1.5 Hz, IH, 8-H), 7.82 (td, 3J = 7.6 Hz, 4J = 1.5 Hz, IH, 6-H), 7.66 (td, 3J = 7.5 Hz, 4J = 1.3 Hz, IH, 7-H), 7.38-7.06 (m, 5H, phenyl H), 3.53 (t, 3J = 7.6 Hz, 2H,

0.40 (CHZCl,), 0.79 [CH2ClZ/AcOEt (9:1)]. - IR: 5 = 3387 (NH),

CHZ-Ph), 3.01 (t, = 7.6 Hz, 2H, COCH2). - I3C NMR: 6 = 203.61 (s, COCHZ), 181.28 (s, GI) , 181.00 (s, C-4), 152.63 (s, C-2), 141.75 [s, phenyl C (@so)], 136.07 (d, C-6), 134.09 (s, C-4a), 132.50 (d, C-7), 129.66 (s, C-Sa), 128.57 [d, phenyl C (ortho)], 128.34 [d, phenyl C (meta)], 127.29 (d, C-5), 126.29 (d, C-8), 125.83 [d, phenyl C (para)], 108.79 (s, C-3), 45.92 (t, CH2-Ph), 30.59 (t, C0CH2). - MS: mlz (%) = 305 (52) [M+], 228 (14), 214 (15), 201 (loo), 200 (24), 173 (98), 172 (27), 91 (31). - CI9Hl5NO3 (305.3): calcd. C 74.74, H 4.95, N 4.59; found C 74.55, H 4.92, N 4.79. 2-Amino-3-phenylacetyl-l,4-naphthoquinone (3d) (0.221 g; 57%),

obtained as brown prisms with m.p. 102-105°C. - Rf = 0.31

(NH), 1670 (CO), 1636, 1602, 1568, 1353, 1308, 1285, 1013, 968, 753, 725, 696 cm-'. - lH NMR: 6 = 10.62 (br. s, 2H, NH2), 7.98 (dd, 3J = 7.3 Hz, 4J = 1.1 Hz, l H , 5-H), 7.88 (dd, 3J = 7.3 Hz, 4J = 1.1 Hz, 1 H, 8-H), 7.54 (td, 3J = 7.3 Hz, 4J = 1.1 Hz, 1 H, 6- H), 7.44 (td, 3J = 7.3 Hz, 4J = 1.1 Hz, 1 H, 7-H), 7.35 (dd, 3J = 7.2 Hz, 4J = 1.2 Hz, l H , phenyl ortho-H), 7.22-7.10 (m, 3H, phenyl meta-H, para-H), 3.38 (s, 2H, CHz). - I3C NMR: 6 =

137.59 [s, phenyl C (@so)], 134.52 (d, C-6), 133.81 (s, C-4a), 132.28 (d, C-7), 130.16 (s, C-Sa), 128.65, 128.01 [2 d, phenyl C (ortho), phenyl C (meta)], 126.50 (d, C-5), 126.48 (d, C-8), 125.83 [d, phenyl C (para)], 113.08 (s, C-3), 38.92 (t, CHz). - MS: rnlz (%) = 291 (27) [M+], 275 (65), 214 (5), 200 (IOO), 172 (26), 149 (5), 105 (48), 91 (34), 77 (81), 68 (12). - CL9HI3NO3 (291.3): calcd. C 74.22, H 4.50, N 4.81; found C 74.11, H 4.32, N 4.68.

(CHZClz), 0.73 [CH2CIZ/AcOEt (9: I)]. - IR: 0 = 3364 (NH), 3265

207.09 (s , COCHZ), 182.35 (s, GI) , 181.23 (s, C-4), 144.47 (s, C-2),

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