Stereochemistry of 1,2‐Oxaphospholanes, VIII. Synthesis, Stereochemistry, and Ring Opening Reactions of Diastereomeric 3‐Hydroxy‐2‐methoxy‐5‐methyl‐1,2‐oxaphospholan‐2‐ones

Abstract

AbstractAddition of dimethyl phosphonate to acetaldol gives a 3 : 7 mixture of diastereomeric dimethyl (1,3‐dihydroxybutyl)phosphonates 3 and 4. The relative configurations at C‐1 and C‐3 in these diols were established by the 13C NMR data of their O‐benzylidene derivatives. Axial preference‐for the dimethoxyphosphoryl substituent at C‐4 of the 1,3‐dioxane ring is observed. A model of the 1,3‐asymmetric induction for the Abramov reaction is proposed. Intramolecular transesterification of the phosphonates 3 and 4 in the presence of equimolar amounts of triethylamine affords diastereomeric 3‐hydroxy‐2‐methoxy‐5‐methyl‐1,2‐oxaphospholan‐2‐ones. 1,2‐Oxaphospholane ring opening reactions of the title compounds were studied by 31P NMR.