Formation of a New Zwitterionic Phosphorus Compound using Buⁿ₃P and COS

Abstract

We have recently reported the use of the crystalline tri-n-butylphosphine-carbon disulfide adduct to form a variety of heterocyclic compounds including dithiole-containing ylides,¹ 2-alkylidene- 1.3-dithiolanes,² and dihydrotetrathiafulvalenes³. In particular reaction with DMAD gave the dithiole-containing ylide shown¹. We now describe the corresponding reaction of triburylphosphine and carbonyl sulfide, COS, with a variety of unsaturated systems which generally takes a completely different course as shown for the example of DMAD below. The structure of the unusual zwitterionic product has been confirmed by X-ray diffraction and is shown.