Cyclic organophosphorus compounds. Part XIV. A proton magnetic resonance study of the stereochemistry of some 5,5-di- and 4,5,5-tri-substituted 1,3,2-dioxaphosph(V)orinans

Abstract

4,4-Dimethyl-2,7,8-trioxa-1-phosphabicyclo[3,2,1]octane and its 5-deuterio-derivative have been prepared and converted by chlorination followed by treatment with piperidine into trans-4-chloromethyl-5,5-dimethyl-2-oxo-2-piperidino-1,3,2-dioxaphosphorinan and its 4-deuterio-derivative. ¹H N.m.r. data suggest that this piperidide and the intermediate monocyclic phosphorochloridate, as well as trans-5-chloromethyl-5-methyl-2-oxo-2-piperidino-1,3,2-dioxaphosphorinan, exist with the phosphorus-containing ring held in a rigid chair form. On the other hand the cis-stereoisomers of 4-chloromethyl-5,5-dimethyl-2-oxo-2-piperidino-(again demonstrated by use of the 4-deuterio-compound), 5-chloromethyl-5-methyl-2-oxo-2-piperidino-, and 2-chloro-5-chloro-methyl-5-methyl-2-oxo-1,3,2-dioxaphosphorinan probably possess a twist ring.