Exploring the reaction of multifunctional allylic bromides with N,S-dinucleophiles: isothiouronium salts and analogs as useful motifs to assemble the 1,3-thiazine core

Abstract

The reactivity profile of allylic bromides (derived from the Morita-Baylis-Hillman reaction) towards thiourea derivatives and further transformations of the resulting isothiuronium bromides are described. Isothiuronium salts, prepared in near quantitative yields, undergo a selective acetylation or a base-promoted intramolecular cyclization to give 2-amino-1,3-thiazin-4-ones in good overall yields. Besides the simplicity of the reaction, conditions, and purification steps, the methods presented here furnished high-purity products. The structural characterization of representative compounds was unequivocally confirmed by X-ray diffraction analysis.