Dimethyl sulfoxide , Krapcho

Decarboxylation of (bromodifluoromethyl)malonates (9) reminiscent of Krapcho s deal-koxycarbonylation process, is observed on treatment with potassium fluoride in dimethyl sulfoxide at 170 °C to give 2-(trifluoromethyl)-substituted esters 10.43 The precursors are prepared by reacting diethyl malonates 8 with dibromodifluoromethane in the presence of sodium hydride. The exchange of bromine for fluorine in 9 followed by decarboxylation is an excellent method of introducing a trifluoromethyl group a- to an ester group. 

Krapcho, A. P., Lovey, A. J. Decarbalkoxylations of geminal diesters, P-keto esters, and a-cyano esters effected by sodium chloride in dimethyl sulfoxide. Tetrahedron Lett. 1973, 957-960. 

Krapcho, A. P., Gadamasetti, G. Facile de-tert-butoxycarbonylations of P-keto esters and mixed malonate esters using water in dimethyl sulfoxide. J. Org. Chem. 1987, 52,1880-1881. 

Krapcho, A. P., Weimaster, J. F., Eldridge, J. M., Jahngen, E. G. E., Jr., Lovey, A. J., Stephens, W. P. Synthetic applications and mechanism studies of the decarbalkoxylations of geminal diesters and related systems effected in dimethyl sulfoxide by water and/or by water with added salts. J. Org. Chem. 1978,43, 138-147. 

In 1967, Krapcho reported the utility of a method for decarboxylating geminal diesters using a salt such as NaCN dissolved in a polar aprotic solvent like dimethyl sulfoxide (DMSO). The reaction was discovered when an attempt to effect the following substitution reaction with 1 resulted in decarbomethoxylation to give 2.2 Shortly thereafter, a comprehensive study of decarbalkoxylations using mono- and di-substituted malonates was published.3... 

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