Reactions of salicylaldiimines with propylene chlorophosphites

Abstract

Previously it has been found that the reaction of salicylalcyclohexanediimine with 2-chloro-1,3,2-dioxaphospholane proceeds as a cascade process involving the intramolecular transannular bond N→P to form the tetracyclic hexacoordinated phosphorus derivatives [1]. We attempted to use 2-chloro-1,3,2-dioxaphosphorinane II and its dimethylated derivative III as a phosphorylating agent in the reaction with salicylaldiimines Ia and Ib. The reactions proceed smoothly in a methylene chloride medium at room temperature to yield salts IVa–IVc as single diastereomers. This is proved by the P NMR spectra of the reaction mixtures containing singlet peaks in the range of –139 to – 142 ppm. The cascade cyclization is highly stereoselective, since compounds IVa–IVc containing two chiral centers (the carbon and phosphorus atoms) are formed as single diastereomers.