Rj. Petroski et D. Weisleder, Improved Horner-Wadsworth-Emmons preparation of alpha-methyl- or alpha-ethyl-alpha,beta-unsaturated esters from aldehydes, SYN COMMUN, 31(1), 2001, pp. 89-95
The E-isomer selectivity of the Horner-Wadsworth-Emmons olefination of alde
hydes to form alpha -methyl- or alpha -ethyl-alpha,beta -unsaturated esters
has been improved by using lithium tert-butoxide as the base, triethyl-2-p
hosphonopropionate or triethyl-2-phosphonobutyrate as the phosphonate, an a
ldehyde, and hexane as the reaction solvent. Greater E-isomer selectivity w
as observed in the formation of alpha -methyl-alpha,beta -unsaturated eater
s than alpha -ethyl-alpha,beta -unsaturated esters. These compounds are use
ful intermediates for the synthesis of insect pheromones and natural produc
ts.