Phosphonate–Phosphinate Rearrangement

Abstract

LiTMP metalated dimethyl <i>N</i>-Boc-phosphoramidates derived from 1-phenyl­ethylamine and 1,2,3,4-tetrahydro­naphthalen-1-ylamine highly selectively at the CH₃O group to generate short-lived oxymethyllithiums. These isomerized to diastereomeric hydroxy­methyl­phosphonamidates (phosphate–phosphonate rearrangement). However, <i>s</i>-BuLi converted the dimethyl <i>N</i>-Boc-phosphoramidate derived from 1-phenylethylamine to the <i>N</i>-Boc α-aminophosphonate preferentially. Only <i>s</i>-BuLi deprotonated dimethyl hydroxymethyl­phosphonamidates at the benzylic position and dimethyl <i>N</i>-Boc α-aminophosphonates at the CH₃O group to induce phosphonate–phosphinate rearrangements. In the former case, the migration of the phosphorus substituent from the nitrogen to the carbon atom followed a retentive course with some racemization because of the involvement of a benzyllithium as an intermediate