2,3,5,6-tetramethyl-1<i>H</i>,4<i>h</i>-3a,6a-diaza-1,4-diphosphapentalene and its 1,4-dichloro derivative: specifics of synthetic approaches

Abstract

Reaction of azine-2-butanone with PCl3 in THF or methylene chloride gives a mixture of isomeric diazadiphosphapentalene dichlorides. Carrying out the reaction without solvent leads to 1,4-dichloro-2,5,3,6-tetramethyl-1 H ,4 H -3a,6a-diaza-1,4-diphosphapentalene (DDPCl2) (32%) and the cleavage product of the heteropentalene backbone - 4,5-dimethyl-2 H -1,2,3-diazaphospholium chloride (29%), while in acetonitrile the only reaction product is dichloride DDPCl2 (60%). The reduction of the latter with manganese powder in tetrahydrofuran leads to 2,5,3,6-tetramethyl-1 H ,4 H -3a,6a-diaza-1,4-diphosphapentalene in 57% yield. The products were investigated by X-ray diffraction analysis and cyclic voltammetry method.