Stereochemistry of organophosphorus cyclic compounds. Part 5. Synthesis and geometry of some 4,5-disubstituted 1,3,2-dioxaphospholan-2-thiones and stereochemistry of nucleophilic displacement reactions at phosphorus

Abstract

Geometrical isomers of 2-hydroxy-4,5-dimethyl-1,3,2-dioxaphospholan-2-thione. 2-halogeno-4,5-dimethyl-1,3,2-dioxaphospholan-2-thione (X= Cl, Br, or F) and 2-hydroxy-4,5-diphenyl-1,3,2-dioxaphospholan-2-thione have been prepared in a stereospecific manner. Stereochemistries of these isomers are assigned on the basis of chemical correlations and n.m.r. measurements. 2-Chloro- and 2-bromo-4,5-dimethyl-1,3,2-dioxaphospholan-2-thione have been found to undergo methanolysis, aminolysis, and mercaptolysis with retention of configuration at phosphorus. Halogen–halogen exchange at the phosphorus atom is also described. The relationship between cis-and trans-geometry of disubstituted 1,3,2-dioxaphospholan-2-thiones and their ³¹P and ¹³C n.m.r. spectral parameters is briefly discussed.