A convenient eco-friendly system for the synthesis of 5-sulfenyl tetrazole derivatives of indoles and pyrroles employing CeCl3·7H2O in PEG-400

Abstract

The use of CeCl₃·7H₂O in polyethyleneglycol 400 (PEG-400), as an efficient and eco-friendly promoter system for the convenient synthesis of 5-sulfenyl tetrazoles derived from indoles and pyrroles, is reported. The synthesis entails the [3 + 2] cycloaddition reaction of NaN₃ with 3-thiocyanato indoles (including 3,3′-di-thiocyanato-1H,1H′,2,2′-biindoles) and 2-thiocyanato pyrroles. The thiocyanates were conveniently obtained by the oxone-mediated thiocyanation of differently substituted starting indoles, 1H,1H′,2,2′-biindoles and N-aryl pyrroles with NH₄SCN. The scope and limitations of the transformation were also studied.