SYNTHESIS OF POLYENES VIA PHOSPHONIUM YLIDS

The mechanism of the Wittig reaction is discussed on the basis of recent experimental results. Our observations allow us to predict the stereochemistry of olefines formed by carbonyl olefination with phosphorus y1 ids or phosphonate anions. Deuterium or tritium may be incorporated into the resulting olefines. Synthetic routes to “symmetric” carotenoids by oxidative dimerisation and the synthesis of “unsymmetric” polyenes using polymeric carriers are discussed. Two approaches to ene-yne-compounds via phosphorus ylids are presented. © 1979, Walter de Gruyter. All rights reserved.