Synthesis of quinquevalent phosphoranes from phosphine oxides

Abstract

The salts obtained from phosphine oxides and trifluoromethanesulphonic anhydride give quinquevalent cyclic phosphoranes on treatment with 1,2-diols or catechols in the presence of di-isopropylamine. The method is not successful starting with cyclic phosphonic or phosphinic esters. Spirophosphoranes are obtained from phosphetan sulphides on alkylation with [Me₃O][PF₆] followed by treatment with pyrocatechol, but not with perfluoropinacol, in the presence of di-isopropylamine. The spirophosphorane (25), from 2-phenyl-1,2-oxaphospholan and hexafluoroacetone, is described.