Nucleophilic Substitution of P‑Stereogenic Chlorophosphines: Mechanism, Stereochemistry, and Stereoselective Conversions of Diastereomeric Secondary Phosphine Oxides to Tertiary Phosphines

A diastereomeric mixture of secondary phosphine oxide is stereospecifically converted to chlorophosphine salt by treatment with oxalyl chloride, which stereoselectively affords P-inverted or retained tertiary phosphines, depending on the substitution with aliphatic or aromatic Grignard reagents, respectively, in high to 99% yield and 99:1 dr. The repulsion of π-electron on aryl to lone electron pair on phosphorus is proposed for the P-retained substitution.