Cathodically promoted ethynylation of ketones

The addition of acetylene to acetone to form 2-methyl-3-butyn-2-ol was achi eved by cathodic electrolysis with mass yields approaching 90% and current efficiencies as high as 1070% using dimethyl sulfoxide as solvent. Excellen t yields were also obtained for acetylene plus methyl ethyl ketone or 6,10, 14-trimethylpentadecan-2-one. Addition of 2-methyl-3-butyn-2-ol to acetylen e produced significant quantities of the acetylenic diol, 2,5-dimethyl-3-he xyne-2,5-diol, the maximum mass yield being 40% with 206% current efficienc y when acetonitrile was used as solvent. It was also shown that electrolysi s of acetone, under the conditions outlined above, resulted in rapid conver sion to the 11% equilibrium concentration of diacetone alcohol (4-methyl-4- hydroxy-2-pentanone) with a current efficiency exceeding 6000%. It is concl uded that a number of base-catalyzed reactions can be fruitfully carried ou t by cathodic electrolysis. (C) 1999 The Electrochemical Society. S1099-006 2(99)07-004-2. All rights reserved.