Synfacts 2009(4): 0378-0378  
DOI: 10.1055/s-0028-1087894
Synthesis of Heterocycles
© Georg Thieme Verlag Stuttgart ˙ New York

Synthesis of Benzothiazines via an Intramolecular Thioamide S-Michael Addition

Contributor(s): Victor Snieckus, Jignesh J. Patel
C. Gimbert, A. Vallribera*
Universitat Autònoma de Barcelona, Spain
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Publikationsverlauf

Publikationsdatum:
23. März 2009 (online)

Significance

A synthesis of 4H-3,1-benzothia­zines has been demonstrated through a simple three-step procedure that consists of sequential N-acylation and Mizoroki-Heck reaction of 2-iodoaniline. Reaction of the intermediate with Lawesson’s reagent leads to intramolecular cyclization of the resulting thioamide by an unusual intramolecular S-Michael addition. In the case of perfluoroalkyl derivative (R¹ = C3F7, R² = CO2Et), the reaction was found to be very sluggish (high temperature, excess Lawesson’s reagent and three days of reaction time) and led to dithionated product [R² = C(S)OEt] in low yield.