Synthesis of 1,3-thiazines by a three-component reaction and their transformations into β-lactam-condensed 1,3-thiazine and 1,4-thiazepine derivatives

Variously substituted 1,3-thiazines have been prepared by a three-component reaction involving a thioamide, an aldehyde, and an alkene. Two diastereomeric thiazines were transformed by stereoselective Staudinger reaction into the corresponding chloro-β-lactam-condensed-1,3-thiazines, and one of them was rearranged in basic media to afford a highly substituted 1,4-thiazepine. Several of the obtained compounds (six 1,3-thiazines and one β-lactam-condensed-1,3-thiazine) were analyzed by X-ray crystallography, which enabled to assign their spatial arrangement and stereochemistry.