SELECTIVE REDUCTION OF THE ESTER GROUP IN THE 1,3-DITHIOL-2-(THI)ONE AND TETRATHIAFULVALENE SERIES - ACCESS TO THE RELATED PHOSPHONIUM SALTS AND THEIR WITTIG REACTIONS

In the 1,3-dithiol-2-(thi)one series, the reduction of the ester funct ionality into the aldehyde or the alcohol ones can be selectively achi eved thanks to diisobutylaluminum hydride (DIBALH) in dichloromethane at controlled low temperature ; when applied in the TTF series such a procedure only gives rise to alcohols in lower yields. From 2-thioxo-4 -hydroxymethyl-1,3-dithiole 3a, the corresponding phosphonium salt 4a is readily prepared, this latter compound being a very nice synthetic intermediate in TTF chemistry thanks to its Wittig reactions. Prelimin ary experiments indicate that this reaction sequence can also be exten ded to the TTF series.