A multinuclear NMR study of the cycloaddition reaction of SNSAsF₆withtert-butylphosphaacetyline (CH₃)₃CCP leading to the 5-tert-butyl-1,3,2,4-dithiazaphospholium cation; a preliminary account of the novel exchange of a cyclic phosphorus by nitrogen in the reaction of with azide N₃⁻leading to 5-tert-butyl-1,3,2,4-dithiadiazolyl

Abstract

Abstract:The cycloaddition reaction of SNS+ (as the AsF6-salt) with 5-tert-butylphosphaacetyline (CH,),CCP n in sulfur dioxide solution at -60°C gave (CH,),CCPSNS+, the first identified example of a 1,3,2,4-dithiazan phospholium heterocycle RCPSNS+. The cycloadduct was characterized by multinuclear NMR ('H, 13c, 1 4~, n 1 5~, ,'P) spectroscopy at low temperature. Reduction of IT (CH,),CCPSNS+ in situ with SbPh, in the presence n of Me4NC1 led to a radical, which may be the IT tert-butyl-l,3,2,4-dithiazaphospholyl (CH,),CCPSNS'. The n reaction of 5-tert-butyl-l,3,2,4-dithiazaphospholium (CH,),CCPSNS+ with azide N,-surprisingly gave the n n previously known 5-tert-butyl-l,3,2,4-dithiadiazolyl (CH,),CCNSNS'. The conversion of (CH,),CCPSNS+ to ( C H , ) , C~N S N~ by the net replacement of a cyclic phosphorus with nitrogen is unprecedented.Key words: dithiazaphospholium, dithiazaphospholyl, cycloaddition, multinuclear NMR, ESR.Resume : La rkaction de cycloaddition du SNS+ (sous forme de sel de AsF6-) avec le tert-butylphosphaackn tyline (CH,),CCP en solution dans le bioxyde de soufre i -60°C donne le (CH,),CCpSNS+, qui est le premier n exemple identifit d'un 1,3,2,4-dithiazaphospholium htttrocyclique RCPSNS+. On a caractCrisC i'adduit --

Phospha‐Organic Chemistry: Panorama and Perspectives

“…(42)]. [112] [2þ4] Cycloadditions of phosphaalkynes have also been studied in some depth. The initial [2þ4] cycloadduct is normally unstable and evolves, either to give an aromatic phosphinine [Eq.…”