Phenyl vinyl thioether: A convenient source of the ethylene 1,1-dianion

The successive reaction of phenyl vinyl thioether (1) with n-butyllithium a nd an etectrophile [E-1= PhCHO, (CH2)(4)CO, (CH2)(5)CO] in THF at -78 degre es C gives, after hydrolysis, the expected methylenic hydroxy thioethers (2 ). Deprotonation of 2 with n-butyllithium followed by a DTBB-catalysed lith iation and reaction with a second electrophile [E2= (BuCHO)-Bu-t, PbCHO, Me 2CO. (CH2)(5)CO], also at -78 C, gives after hydrolysis the corresponding m ethylenic 1,3-diols 3. When carbon dioxide is used as the second electrophi le, the expected methylenic hydroxy acid 3cd is isolated. The whole process can be performed in a one-pot manner without isolation of the intermediate s 2. (C) 1999 Elsevier Science Ltd. All rights reserved.