Titanium(II)-based Z-reduction of alkynes. Syntheses of deuterium labelled linolenic and oleic acids and (3E,8Z,11Z)-tetradeca-3,8,11-trienyl acetate, the sex pheromone of a tomato pest, Scrobipalpuloides absoluta

Abstract

An operationally simple Ti^II-mediated, stereo- and regio-specific reduction of isolated, conjugated and methylene ‘skipped’ polyynes to the corresponding Z-polyenes in a one-pot procedure is described and applied inter alia to the syntheses of deuterium labelled linolenic and oleic acids. Final quenching with D₂O (instead of H₂O) results in regio- and stereo-specific Z-dideuteration of the alkyne. The synthesis of (3E,8Z,11Z)-tetradeca-3,8,11-trienyl acetate, the major sex pheromone of Scrobipalpuloides absoluta, a destructive pest of tomatoes, and the (3Z,8Z,11Z)-isomer, utilises this methodology in key reduction steps, and under- or over-reduction are negligible.