A NEW SYNTHESIS OF FUNCTIONALIZED IMIDAZO [2,1-B][1,3] THIAZINES WITH THIOHYDANTOINS, ISOCYANIDES AND DIALKYL ACETYLENEDICARBOXYLATES

Introduction 1,3-thiazines possess strong analgesic and muscle relaxing properties. They have also stimulation of the entire sympathetic system, hypothermic activities and other pharmaceuticals [1-2]. Investigations in another laboratory have shown that the zwitterionic intermediate generated by the reaction of nucleophilic carbenes such as isocyanides and dimethyl acety lenedicarboxylate (DMAD) underwent facile addition to aldehydes and quinines to afford highly functionalized novel aminofurans and iminolactones in good yields [3]. As part of our current studies on the development of new routes in heterocyclic synthesis [4-5], we report the results of our studies involving the reaction of the zwitterionic intermediates derived from alkyl isocyanides 3 and acety lenic esters 2 with 5,5-diaryl-2thioxoimidazolidin-4-one 1, which constitutes a synthesis of dialkyl 7-(alkylimino)-3,5,6,7tetrahydro-3-oxo-2,2-diaryyl-2H-imidazo[2,1-b][1,3]thiazine-5,6-dicarboxylate 4 in 80-91% yields. Then, this compound 4 undergo a smooth reaction in boiling toluene in the presence of catalytic amount of p -TSA to produce 5 (see Scheme and Table 1).