STEREOSELECTIVE SYNTHESIS OF 2-ALKYLIDENE-3,4-DIHYDRO-3-OXO-2H-1,4-BENZOTHIAZINES

Article abstract of DOI:10.1016/0040-4020(82)80193-2

Metallation of 4-methyl-3,4-dihydro-3-oxo-2H-1,4-benzothiazine with LDA and subsequent reaction with aldehydes leads to diastereomeric aldols 4 and 5.Acetylation followed by acetic acid elimination of the aldols provides a stereoselective and high yield route to 2-alkylidene-3,4-dihydro-3-oxo-2H-1,4-benzothiazines.