Zur Synthese von 6-nitrosubstituierten 2H-Benzo[b]thiopyran-Derivaten aus 2-Mercapto-5-nitro-benzaldehyd

Abstract

About the Synthesis of 6-nitro-substituted 2H-Benzo[b]thiopyran Derivatives Starting from 2-Mercapto-5-nitro-benzaldehyde Benzene derivatives useful as C3S-building blocks for the synthesis of 2H-benzo[b]thiopyrans are not easily available. The synthesis starting with 2-chloro-benzaldehyde via 2-chloro-5-nitrobenzalde-hyde to 2-mercapto-5-nitro-benzaldehyde-tert-butylimin 1b and its cyclisation to 2H-benzo[b]thiopyrans (2a – h) and (3a – d) is described. By reaction with acceptor substituted alkenes, e.g. acroleine or ω-nitrostyrene respectively 2-chloro-propenes, e.g. substituted ß-chloroacroleines or 2-chloro-propene-1,3-dicarboxylates the compounds 2a – h and 3a – d are obtained. Vilsmeier's reaction of the diester 3d with DMF/POCl3 yields the formyl compound 4.