The thioacyl isocyanate–acyl isothiocyanate rearrangement

Abstract

The title rearrangement, involving a 1,3-shift of a substituent on an acyl(thioacyl) group is investigated computationally at ab initio and DFT levels of theory (G2(MP2,SVP) and B3LYP/6-31G*). The computed order of migratory aptitudes is Br > Cl > NMe₂ > F, SCH₃, SH > OMe, NH₂ > OH ≫ H ≫ Me, in good agreement with experimental data reported by Goerdeler. The acyl isothiocyanates are of lower energy than the thioacyl isocyanates, but in many cases an equilibrium between the two is achievable.