Table 2 (continued)
currently investigating this possibility, as well as the extension
of our methodology to other substrates.
Entry
Benzoic acid
Product
Yield (%)b
During the processing of this manuscript another methodology
describing the protodecarboxylation of carboxylic acids with
silver salts has been reported.12
13d
96
We gratefully acknowledge QMUL for a studentship (J. C.),
the Engineering and Physical Sciences Research Council and
the Royal Society for generous funding, the Generalitat de
Catalunya (C. S.) and the Universitat de Barcelona for a
travel bursary (C. S.), the Nuffield Foundation for an under-
graduate research bursary (D. B.) and Dr S. M. Goldup for
discussions.
14
71
95
Notes and references
15c
1 For recent examples, see: (a) H. A. Chiong, Q.-N. Pham and
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1996, 109.
2 E. M. O’Brien, B. J. Morgan and M. Kozlowski, Angew. Chem.,
Int. Ed., 2008, 47, 6877.
16
17
0
0
3 (a) T. Cohen and R. A. Schambach, J. Am. Chem. Soc., 1970, 92,
3189; (b) T. Cohen, R. W. Berninger and J. T. Wood, J. Org.
Chem., 1978, 43, 837; (c) J. Chodowska-Palicka and M. Nilsson,
Acta Chem. Scand., 1970, 24, 3353; (d) J. Chodowska-Palicka and
M. Nilsson, Acta Chem. Scand., 1971, 25, 3451; (e) A. Cairncross,
J. R. Roland, R. M. Henderson and W. A. Sheppard, J. Am. Chem.
Soc., 1970, 92, 3187.
4 G. B. Deacon, M. F. O’Donoghue, G. N. Stretton and
J. M. Miller, J. Organomet. Chem., 1982, 233, C1.
5 (a) L. J. Gooßen, G. Deng and L. M. Levy, Science, 2006, 313, 662;
(b) L. J. Gooßen, N. Rodriguez, B. Melzer, C. Linder, G. Deng and
L. M. Levy, J. Am. Chem. Soc., 2007, 129, 4824; (c) L. J. Gooßen,
F. Manjolinho, B. A. Khan and N. Rodriguez, J. Org. Chem.,
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C. Linder and B. Melzer, Adv. Synth. Catal., 2007, 349, 2241.
6 J. S. Dickstein, C. A. Mulrooney, E. M. O’Brien, B. J. Morgan and
M. Kozlowski, Org. Lett., 2007, 9, 2441.
18
0
a
Unless otherwise noted, all the reactions were carried out with
10 mol% Ag2CO3 and 1.0 equiv. of benzoic acid in a 0.2 M DMSO
b
c
solution at 120 1C for 16 h. Yields of isolated pure material. This
product was found to be volatile. The reaction was carried out in a
sealed vessel and the yield was determined by 1H NMR analysis using
7 For the palladium-catalysed decarboxylation of p-hydroxybenzoic
acid, see: A. A. Nunez Magro, G. R. Eastham and D. J. Cole-
Hamilton, Dalton Trans., 2009, 4683.
d
an internal standard. The reaction was carried out at 140 1C.
8 (a) N. Lebrasseur and I. Larrosa, J. Am. Chem. Soc., 2008,
130, 2926; (b) J. Cornella, P. Lu and I. Larrosa, Org. Lett., 2009,
DOI: 10.1021/ol902304n.
9 (a) R. G. Johnson and R. K. Ingham, Chem. Rev., 1956, 56, 219;
(b) D. Crich, in Comprehensive Organic Synthesis, ed. B. M. Trost
and V. L. Steven, Pergamon, Oxford, vol. 7, 1991.
(91% yield) was obtained without any adjustment to the
procedure being required.
10 For selected examples, see: (a) A. G. Myers, D. Tanaka and
M. R. Mannion, J. Am. Chem. Soc., 2002, 124, 11250;
(b) D. Tanaka and A. G. Myers, Org. Lett., 2004, 6, 433;
(c) D. Tanaka, A. S. P. Romeril and A. G. Myers, J. Am. Chem.
Soc., 2005, 127, 10323; (d) J.-M. Becht, C. Catala, C. L. Drian and
A. Wagner, Org. Lett., 2007, 9, 1781; (e) J.-M. Becht and
C. L. Drian, Org. Lett., 2008, 10, 3161; (f) A. Voutchkova,
A. Coplin, N. E. Leadbeater and R. H. Crabtree, Chem. Commun.,
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2009, 131, 4194; (h) Z. Wang, Q. Ding, X. He and J. Wu,
Tetrahedron, 2009, 65, 4635.
In conclusion, we have developed a mild and simple
methodology for the silver-catalysed protodecarboxylation
of ortho-substituted benzoic acids that is compatible with a
range of functionalities, such as halogens, NO2, alkoxides, and
even unprotected phenols and amines. Although the exact
reasons for an ortho-substituent being required are still
under examination, they are most likely to be electronic.
Furthermore, these results suggest that decarboxylative
cross-coupling reactions using a Pd/Ag system may actually
proceed via a silver-promoted decarboxylation, instead of
the commonly-invoked palladium-catalysed pathway. We are
11 W. T. Miller and K. K. Sun, J. Am. Chem. Soc., 1970, 92, 6985.
12 L. J. Gooben, C. Linder, N. Rodriguez, P. P. Lange and
A. Fromm, Chem. Commun., 2009, DOI: 10.1039/b912509d.
ꢀc
This journal is The Royal Society of Chemistry 2009
7178 | Chem. Commun., 2009, 7176–7178