ORGANIC
LETTERS
2009
Vol. 11, No. 24
5710-5713
Silver-Catalyzed Protodecarboxylation of
Heteroaromatic Carboxylic Acids†
Pengfei Lu, Carolina Sanchez, Josep Cornella, and Igor Larrosa*
School of Biological and Chemical Sciences, Queen Mary UniVersity of London,
Joseph Priestley Building, Mile End Road, E1 4NS London, U.K.
Received October 27, 2009
ABSTRACT
A simple and highly efficient protodecarboxylation procedure for a variety of heteroaromatic carboxylic acids catalyzed by Ag2CO3 and AcOH
in DMSO is described. This methodology can also perform the selective monoprotodecarboxylation of several aromatic dicarboxylic acids.
Decarboxylation reactions are important transformations in
synthetic organic chemistry,1 especially for the removal of
carboxylate groups that were required as directing groups
in other transformations2 but are not part of the target
molecules.3 Consequently, considerable effort has been
directed to the study of the protodecarboxylation of aromatic
carboxylic acids,4 which usually require the use of transition
metals such as Cu,5 Hg,6 and Pd.7 Among the various
methods, the use of Cu/quinoline systems is most widely
adopted following the seminal work by Shepard et al. on
the protodecarboxylation of halofuroic acids promoted by
stoichiometric Cu(0).5a,8 Subsequently, the protodecarboxy-
lations of thenoic, furoic and indole-2-carboxylic acids were
reported following similar procedures.5c,9 This methodology
has recently been significantly improved by Goossen et al.
with the development of a catalytic Cu(I)/phenanthroline/
quinoline system.10 However, all of these methods suffer
from the same problems, namely, the requirement for
extremely high temperatures (170-200 °C), which limits
substrate compatibility, and the difficulties in isolating the
products from their high boiling point reaction solvents.
During the development of a Pd/Ag bimetallic system for
mild direct arylations11a and decarboxylative arylations of
indoles,11b we observed that Ag salts were able to promote the
protodecarboxylation of aromatic carboxylic acids. As a result,
† Dedicated to the memory of Professor Keith Fagnou.
(1) Joule, J. A.; Mills, K. Heterocyclic Chemistry, 4th ed.; Blackwell
Science: Malden, MA, 2000.
(2) For recent examples, see: (a) Chiong, H. A.; Pham, Q.-N.; Daugulis,
O. J. Am. Chem. Soc. 2007, 129, 9879. (b) Sonoda, M.; Kakiuchi, F.;
Kamatani, A.; Chatani, N.; Murai, S. Chem. Lett. 1996, 25, 109.
(3) O’Brien, E. M.; Morgan, B. J.; Kozlowski, M. Angew. Chem., Int.
Ed. 2008, 47, 6877.
(4) For selected examples, see: (a) Chu, E. J.-H.; Chu, T. C. J. Org.
Chem. 1954, 19, 266. (b) Brown, E. V.; Moser, R. J. J. Org. Chem. 1971,
36, 454. (c) Hirsch, J. A.; Sterner, D. E. J. Org. Chem. 1972, 37, 1678. (d)
Moser, R. J.; Brown, E. V. J. Org. Chem. 1972, 37, 3938. (e) Moser, R. J.;
Brown, E. V. J. Org. Chem. 1972, 37, 3941. (f) An, J.; Bagnell, L.;
Cablewski, T.; Strauss, C. R.; Trainor, R. W. J. Org. Chem. 1997, 62, 2505.
(g) Sharma, A.; Kumar, R.; Sharma, N.; Kumar, V.; Sinha, A. K. AdV.
Synth. Catal. 2008, 350, 2910. (h) Mundle, S. O. C.; Kluger, R. J. Am.
Chem. Soc. 2009, 131, 11674.
(6) (a) Dodd, D.; Johnson, M. D. J. Chem. Soc. B 1970, 1337. (b) Moseley,
J. D.; Gilday, J. P. Tetrahedron 2006, 62, 4690 and references therein
.
(7) (a) Matsubara, S.; Yokota, Y.; Oshima, K. Org. Lett. 2004, 6, 2071.
(b) Dickstein, S. J.; Mulrooney, C. A.; O’Brien, E. M.; Morgan, B. J.;
Kozlowski, M. C. Org. Lett. 2007, 9, 2441
.
(8) For selected examples of copper-mediated decarboxylations, see: (a)
Beccalli, E. M.; Clerici, F.; Marchesini, A. Tetrahedron 1998, 54, 11675.
(b) Gaukroger, K.; Hadfield, J. A.; Hepworth, L. A.; Lawrencen, N. J.;
McGown, A. T. J. Org. Chem. 2001, 66, 8135. (c) Selvakumar, N.; Rajulu,
G. G. J. Org. Chem. 2004, 69, 4429. (d) Gooꢀen, L. J.; Deng, G.; Levy,
(5) (a) Shepard, A. F.; Winslow, N. R.; Johnson, J. R. J. Am. Chem.
Soc. 1930, 52, 2083. (b) Nilsson, M. Acta Chem. Scand. 1966, 20, 423. (c)
Nilsson, M.; Ullenius, C. Acta Chem. Scand. 1968, 22, 1998. (d) Cairncross,
A.; Roland, J. R.; Henderson, R. M.; Sheppard, W. A. J. Am. Chem. Soc.
1970, 92, 3187. For some mechanistic studies, see: (e) Cohen, T.;
Schambach, R. A. J. Am. Chem. Soc. 1970, 92, 3189. (f) Cohen, T.;
Berninger, R. W.; Wood, J. T. J. Org. Chem. 1978, 43, 837.
L. M. Science 2006, 313, 662
.
(9) Jones, G. B.; Chapman, B. J. J. Org. Chem. 1993, 58, 5558
.
(10) (a) Gooꢀen, L. J.; Thiel, W. R.; Rodriguez, N.; Linder, C.; Melzer,
B. AdV. Synth. Catal. 2007, 349, 2241. (b) Goossen, L. J.; Manjolinho, F.;
Khan, B. A.; Rodriguez, N. J. Org. Chem. 2009, 74, 2620.
10.1021/ol902482p 2009 American Chemical Society
Published on Web 11/18/2009