IMPROVED HORNER-WADSWORTH-EMMONS PREPARATION OF α-METHYL- OR α-ETHYL-α,β-UNSATURATED ESTERS FROM ALDEHYDES

The E-isomer selectivity of the Horner-Wadsworth-Emmons olefination of aldehydes to form α-methyl- or α-ethyl-α,β-unsaturated esters has been improved by using lithium tert-butoxide as the base, triethyl-2-phosphonopropionate or triethyl-2-phospho-nobutyrate as the phosphonate, an aldehyde, and hexane as the reaction solvent. Greater E-isomer selectivity was observed in the formation of α-methyl-α,β-unsaturated esters than α-ethyl-α,β-unsaturated esters. These compounds are useful intermediates for the synthesis of insect pheromones and natural products.