Microwave-Assisted Synthesis of 2-Substituted 2-Thiazolines and 5,6-Dihydro-4H-1,3-thiazines

Abstract

An efficient and general method for the synthesis of 2-substituted thiazolines and 5,6-dihydro-4H-1,3-thiazines is developed via microwave-assisted ring closure of ω-thioamidoalcohols promoted by ethyl polyphosphate (PPE). The cyclization reaction involves an SN2-type mechanism and features the advantages of very short reaction times, high yields and a predictable stereochemical outcome. The acyclic precursors are prepared in high overall yields by an improved diacylation–thionation–saponification sequence from commercially available ω-amino­alcohols. The whole process is metal-free and operationally simple.