1574
J . Org. Chem. 2002, 67, 1574-1579
Micr ow a ve Sp ecific Wolff Rea r r a n gem en t of r-Dia zok eton es a n d
Its Releva n ce to th e Non th er m a l a n d Th er m a l Effect†
Surendra G. Sudrik,*,‡ Sambhaji P. Chavan,‡ K. R. S. Chandrakumar,§ Sourav Pal,§
Sadgopal K. Date,§ Subhash P. Chavan,‡ and Harikisan R. Sonawane*,‡,|
Division of Organic Chemistry: Technology, and Physical Chemistry Division,
National Chemical Laboratory, Pune-411 008, India
spchavan@dalton.ncl.res.in
Received September 25, 2001
R-Diazoketones possess high electric dipole moments, as a consequence of the dipolar nature of the
diazocarbonyl functional group. The vectorial analysis, theoretical calculations (PM3 and ab initio),
and literature reports based on experimental and theoretical calculations reveal a higher dipole
moment for the Z-configuration of the diazo functional group. Microwave irradiation of R-diazoketone
(1a -m ) (Figure 1) promotes Wolff rearrangement specifically via the Z-configuration in excellent
yields. The dielectric properties of the solvent govern the course of the microwave rearrangement.
3-Diazocamphor (1m ) on microwave irradiation in benzylamine exhibits nonthermal effects to
furnish exclusively the Wolff rearrangement product (4m ), equivalent to its photochemical behavior.
In the presence of an aqueous medium, through solvent heating predominates, leading to the
formation of a tricyclic ketone (5) as the principal product, arising from an intramolecular C-H
insertion. This behavior is similar to its known thermal and transition metal catalyzed reactivity
pattern.
Wolff rearrangement1 of R-diazoketones is an integral
with conducting the reaction at higher temperature (in
the vicinity of 180 °C) such as thermal instability of the
ring-contracted products or ketene intermediates and
other competing side reactions of carbene occurring at
lower temperatures, resulting in the overall poor yield
of the rearranged products. These disadvantages were
largely overcome by photolysis of the diazocarbonyl
functional group in the ultraviolet region (λ ∼ 300 nm);
however, a limit is reached when either the product or
diazocarbonyl substrates contain other photolabile groups.
Among transition metal catalysis, an efficient procedure
developed by Newman et al.5 comprising silver ion
catalysis in the presence of triethylamine under homo-
geneous conditions is generally preferred.
part of the well-known Arndt-Eistert one-carbon homo-
logation of carboxylic acids as well as providing an
efficient route to the ring-contracted compounds from
cyclic R-diazo carbonyl compounds. Literature is replete
with its application in organic synthesis.1,2 The rear-
rangement involves specific 1,2-shift, accompanying or
following loss of dinitrogen, to ketene via a transient free
keto-carbene intermediate. The reaction can be initiated
thermally,3 photochemically,4 by transition metal cataly-
sis,5,6 or by ultrasound in the presence of silver ions.7
Among these, thermolysis is used less frequently than
the other techniques despite simplicity in operational
conditions due to the several disadvantages associated
Recent years have witnessed the advent of microwave
dielectric heating as the superior technique over the
conventional conduction, convection, and radiation modes
of heating. Several organic reactions8 were performed in
the presence of microwave absorptive solvents or in the
presence of additives such as transition metal salts and
completed in minutes with good yields due to the
tremendous acceleration in the rate of reaction. Further-
more, with few exceptions9 the product selectivity ob-
tained in the conventional thermal mode of the reaction
remain unchanged. Recent review articles10 give an
† Dedicated to Prof. G. S. Sudrik, VJ TI, Mumbai, India.
‡ Division of Organic Chemistry: Technology.
§ Physical Chemistry Division.
| Fax: 91-20-5893614.
(1) For reviews, see: (a) Ye, T.; Mckervey, M. A. Chem. Rev. 1994,
94, 1091. (b) Gill, G. B. In Comprehensive Organic Synthesis; Trost,
B. M., Fleming, I., Eds.; Pergamon Press: Oxford, 1991; Vol. 3, p 887.
(c) Regitz, M.; Maas, G. Diazo Compounds; Academic Press: New York;
1986. (d) Ando, W. In The Chemistry of Diazonium and Diazogroups;
Patai, S., Ed.; J ohn Wiley: Chichester, 1978; Part 1, p 458. (e) Meier,
H.; Zeller, K. P. Angew. Chem., Int. Ed. Engl. 1975, 14, 32. (f) Bachman,
W. E.; Strove, W. S. Org. React. (N.Y.) 1942, 1, 38.
(2) (a) Matthews, J . L.; Braun, C.; Guibourdenche, C.; Overband,
M.; Seebach, D. In Enantioselective Synthesis of â-amino acids;
J uaristie, E., Ed.; Wiley-VCH: New York, 1996. (b) Sonawane, H. R.;
Bellur, N. S.; Ahuja, J . R.; Kulkarni, D. G. J . Org. Chem. 1991, 36,
1431. (c) Sudrik, S. G.; Nanjundiah, B. S.; Sonawane, H. R. Indian J
Chem 1997, 36B, 1103.
(3) Wilds, A. L.; Meader, A. L. J . Org. Chem. 1948, 13, 3.
(4) Vleggaar, J . J . M.; Huizer, A. H.; kraakman, P. A.; Nijssen, W.
P. M.; Visser, R. J .; Verma, C. A. G. O. J . Am. Chem. Soc. 1994, 116,
11754.
(5) (a) Lee, V.; Newman, M. S. Org. Synth. (N.Y.) 1970, 50, 77. (b)
Newman, M. S.; Beal, F. J . Am. Chem. Soc. 1950, 72, 5163. (c)
Newman, M. S.; Arkell, A. J . Org. Chem. 1959, 24, 385.
(6) Maas, G. In Houben-weyl Methodender Organischen Chemie,
Carbene; Regitz, M., Ed.; Theime: Stutgart, 1989; E19b, p 2.
(7) Muller, A.; Vogt, C.; Sewald, N. Synthesis 1998, 837.
(8) (a) Marquie, J .; Laporterie, A.; Duhac, J . J . Org. Chem. 2001,
66, 421. (b) Loupy, A.; Petit, A.; Hamelin, J .; Texier-Boullet, F.;
J acquault, P.; Mathe, D. Synthesis 1998, 1213. (c) Caddick, S.
Tetrahedron 1995, 51, 10403. (d) Strauss, C. R.; Trainor, R. W. Aust.
J . Chem. 1995, 48, 1665. (e) Gedye, R. N.; Rank, W.; Westaway, R. C.
Can J Chem. 1991, 69, 706. (f) Abramovitch, R. A. Org. Prep. Proc.
Int. 1991, 23, 683. (g) Larhed, M.; Hallberg, A. J . Org. Chem. 1996,
23, 683. (h) Gigure, R. J .; Bray, T. R.; Duncan, S. M. Tetrahedron Lett.
1986, 27, 4945.
(9) (a) Morcuende, A.; Ors, M.; Valverde, S.; Herradon, B. J . Org.
Chem. 1996, 61, 5264. (b) Pagnotta, M.; Pooley, C. L. F.; Gurland, B.;
Choi, M. J Phys. Org. Chem. 1993, 6, 407. (c) Deka, N.; Sarma, J . C.
J . Org. Chem. 2001, 66, 1947.
10.1021/jo010951a CCC: $22.00 © 2002 American Chemical Society
Published on Web 02/12/2002