Z -Selective Horner−Wadsworth−Emmons Reaction of α-Substituted Ethyl (Diarylphosphono)acetates with Aldehydes 1

New Horner−Wadsworth−Emmons reagents, ethyl 2-(diarylphosphono)propionates ( 2 ), ethyl 2-(diarylphosphono)hexanoates ( 3 ), and ethyl 2-(diarylphosphono)-3-methylbutanoates ( 4 ) were prepared by alkylation of ethyl (diarylphosphono)acetates. The reaction of 2 − 4 with various types of aldehydes gave Z -α,β-dialkyl-α,β-unsaturated esters highly selectively. Remarkable temperature-dependent selectivity was observed in the reaction of (PhO) 2 P(O)CHBuCO 2 Et with octyl aldehyde.