Chemoselectivity in the synthesis of thiocyanates and isothiocyanates: the reaction of alkenes with benzeneselenenyl thiocyanate in methylene chloride

Abstract

The reactions of benzeneselenenyl thiocyanate with some simple alkylsubstituted acyclic and cyclic alkenes have been investigated, and the relative distribution of isomeric adducts determined. The relative distribution of β-thiocyanatoalkyl phenyl selenide to β-isothiocyanatoalkyl phenyl selenide is found to be dependent upon the degree of substitution of the initial alkene. Thus mono- and disubstituted alkenes favour formation of the thiocyanato species, whereas tri- and tetrasubstituted alkenes yield isothiocyanato adducts almost exclusively. Stereospecific anti addition was established in all cases except that of tricyclo[4.2.2.0^2,5]deca-3,9-diene-7,8-dicarboxylic anhydride which gives a 33:67 mixture of cis and trans adducts.