Relative reactivity and stereoselectivity in the Wittig reactions of substituted benzaldehydes with benzylidenetriphenylphosphorane

Abstract

Carbonyl carbon-14 kinetic isotope effects and substituent effects on the relative reactivity and on the cis-trans product ratio were determined in the Wittig reaction of XC 6 H 4 CHO with Ph 3 P=CHC 6 H 4 Y in THF at 0 o C. The isotope effect and the Hammett ρ value were positive under both Li salt-free ( 12 k/ 14 k=1.060±0.003 and ρ x =2.77±0.15) and Li salt-present ( 12 k/ 14 k=1.015±0.004 and ρ x =1.38±0,12) conditions, although they were much larger in the former case