Treatment of esters with diisobutylaluminum hydride (DIBAL) in the presence of lithio-trialkylphosphonoacetate results in improved yields of the homologated a,B-unsaturated esters. The problematic overreduction, which has previously observed in the half reduction of esters using DIBAL, is minimal (~3%) under these conditions. yield of methyl cinnamate under our standard reaction conditions and significant amounts of overreduction products are obtained. Under similar conditions (THF -78'C) the reduction/olefination of methyl 2-octenate gives only a poor yield of conjugated diene. However, this methodology is not limited to saturated esters as simply running the reaction at O"C, under otherwise identical conditions, leads to formation of these conjugated diene ester in 70% yield. -COOCH, 1.0 eq DIBAL * [(EtO)2P(0)CHC02Et~ Lie e cooC,H, (2) THF 0 OC The intramolecular Wittig olefination provides an efficient macrocyclization procedure, however, the aldehyde substrates are often difficult to prepare.6 This present methodology permits the more readily accessible ester to be used in place of an aldehyde. This reduction/olefination of the readily prepared phosphonate diesters should yield the macrocyclic unsaturated lactone. Further studies on the applications of this chemistry are in progress. oJ(/!(oEt)* 0 L c 1981, 12, 4929-4932;