A synthesis of disubstituted acetylenes, and its application to the stereoselective synthesis of conjugated trienes

Abstract

Representative β-oxo-sulphones were obtained by (a) oxidation of β-hydroxy-sulphones, (b) oxidation of α-phenylthio-ketones, and (c) reaction of metallated sulphones with saturated and αβ-unsaturated esters. The β-oxo-sulphones were converted by way of lithium (in one example, sodium) enolates into enol phosphates, which on reductive elimination provided disubstituted acetylenes in moderate to good yield. The sequence permits the preparation of acetylenes R¹CCR² from the primary alcohols RCH₂OH or equivalents.

The value of the method is illustrated by a highly stereoselective synthesis from (E)-geraniol of the conjugated E,Z,E-triene (34) with retention of the original E-geometry.