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Communication | Regular issue | Vol 23, No. 7, 1985, pp.1619-1623
Published online, 1st January, 1970
DOI: 10.3987/R-1985-07-1619
Synthesis of Pirido[2,1-c][1,4]benzothiazines by Reaction between 3-Alkoxycarbonylmethylene-4H-1,4-benzothiazines (β-Enamine Esters) and Dimethyl Acetylenedicarboxylate (DMAD)

Giuseppe Trapani,* Antonia Reho, Andrea Latrofa, Flaviano Morlacchi, and Gaetano Liso

*Dipartimento Farmaco-Chimico, Facolta di Farmacia, Università digli Studi di Bari, Via Orabona 4, I-70125 Bari, Italy


By the title reaction pyrido[2,1-c][1,4]benzothiazines 3d,e and 4 together with dienamine esters 2d,e,f respectively are obtained. The latter compounds are Z,E Michael adducts of the enamine esters 1d-f to DMAD, and are cyclized in high yield to the former compounds by using p-toluenesulfonic acid as catalyst. Starting from benzothiazine 1f the phenothiazine 5 is also obtained.