ORGANIC
LETTERS
2008
Vol. 10, No. 13
2773-2776
Using Toluates as Simple and Versatile
Radical Precursors
Kevin Lam and Istva´n E. Marko´*
De´partement de Chimie, Baˆtiment LaVoisier, UniVersite´ catholique de LouVain,
Place Louis Pasteur, 1, B-1348 LouVain-la-NeuVe, Belgium
istVan.marko@uclouVain.be
Received April 25, 2008
ABSTRACT
The viability of the toluate moiety as a radical precursor has been examined by studying deoxygenation and cyclization reactions.
For many years, the Barton-McCombie reaction has been
considered as the standard procedure for the reduction of an
alcohol into the corresponding alkane.1 Unfortunately, this
method requires the initial formation of light-sensitive
xanthates, which are subsequently reduced either by the
rather toxic tributyltin hydride or by the trialkylborane/water
system. This last procedure tends to lead to poor reproduc-
ibility.2
in the context of the Julia-Lythgoe olefination.3 Our work
suggested that benzoates could act as radical precursors when
treated with a strong reducing agent. Surprisingly, few
examples of benzoate reductions have been reported in the
literature.4 Special examples have been disclosed by Enholm,
who reduced benzoates R to carbonyls.5 However, in these
cases, the benzoate reduction is not the only possible pathway
since any good leaving group R to the carbonyl function
could be eliminated by the use of reducing metals such as
SmI2.6
For the past few years, our laboratory has been interested
in monoelectronic reductions involving benzoates, especially
Although the mechanism of benzoate reduction has been
studied using electrochemical methods, it is still unclear at
(1) (a) Barton, D. H. R.; McCombie, S. W. J. Chem. Soc., Perkin Trans.
1 1975, 16, 1574. For a review, see: (b) Hartwig, W. Tetrahedron 1983,
39, 2609.
(4) (a) Pulicani, J.-P.; Be´zard, D.; Bourzat, J.-D.; Bouchard, H.; Zucco,
M.; Deprez, D.; Commerc¸on, A. Tetrahedron Lett. 1992, 35, 9717. (b)
Webster, R. D.; Bond, A. M.; Compton, R. G. J. Phys. Chem. 1996, 100,
10288. (c) Webster, R. D.; Bond, A. M. J. Org. Chem. 1997, 62, 1779.
(5) Enholm, E.; Jiang, S. Tetrahedron Lett. 1992, 33, 313.
(6) Molander, G. A.; Hahn, G. J. Org. Chem. 1986, 51, 1135.
(7) Wagenknecht, J. H.; Goodin, R.; Kinlen, P.; Woodard, F. E. J.
Electrochem. Soc. 1984, 131, 1559.
(2) Spiegel, D. A.; Wiberg, K.; Schacherer, L.; Medeiros, M.; Wood, J.
J. Am. Chem. Soc. 2005, 127, 12513.
(3) (a) Marko´, I. E.; Murphy, F.; Meerholz, C.; Dolan, S. Tetrahedron.
Lett. 1996, 37, 2089. (b) Marko´, I. E.; Murphy, F.; Kumps, L.; Ates, A.;
Touillaux, R.; Craig, D.; Carballares, S.; Dolan, S. Tetrahedron 2001, 57,
2609. (c) Pospisil, J.; Pospisil, T.; Marko´, I. E. Org. Lett. 2005, 7, 2373.
(d) Pospisil, J.; Marko´, I. E. J. Am. Chem. Soc 2007, 12, 3516. For a review,
see: (e) Dumeunier, R.; Marko´, I. E. Modern Carbonyl Olefination 2004,
104–150.
(8) Gul’tyai, V. P.; Rubinskaya, T.; Korotaeva, L. Bull. Pol. Acad. Sci.
Chem. 1982, 1499.
10.1021/ol800944p CCC: $40.75
Published on Web 05/29/2008
2008 American Chemical Society