Enantioselective Deprotonation of Benzyl Phosphates by Homochiral Lithium Amide Bases — Configurational Stability of Benzyl Carbanions with a Dialkoxyphosphoryloxy Substituent and Their Rearrangement to Optically Active α‐Hydroxy Phosphonates

Benzyl dialkyl phosphates are deprotonated enantioselectively by homochiral lithium amides of isopropyl(1‐phenylethyl)amine or bis(1‐phenylethyl)amine. The short‐lived benzylic carbanions formed are virtually configurationally stable relative to the rearrangement to optically active phenyl‐hydroxymethylphosphonates. The enantiomeric excesses are up to 50%. The pro‐(S) hydrogen is removed by amides having (S) configuration. Homochiral diethyl (S)‐phenyl[D 1 ]‐methyl phosphate [( S )‐ 16c ] is deprotonated by both LDA and n ‐BuLi with a high primary kinetic isotope effect (k H/D ≈︁ 50) and isomerizes to the corresponding α‐hydroxy phosphonate with an enantiomeric excess of up to 85%.