Ring transformation and cyclization reactions of 1,1-dioxo-1,2-thiazines - syntheses of pyridines and benzo[c]thiazines with new substitution pattern
作者:Hagen Bartossek、Egon Fanghänel
DOI:10.1002/(sici)1521-3897(199905)341:4<403::aid-prac403>3.0.co;2-x
日期:1999.5
In presence of ammonia/ammonium acetate the 3,5-dimethyl-2-phenyl-1, 1-dioxo-1,2-thiazine-4-carbaldehyde (1) reacts with ethyl cyanoacetate to the ethyl 2-cyano-4-[1-methyl-2-methylthio-2-(N-phenylsulfamoyl)vinyl)hexa-2,4-dienoate (3) and the Knoevenagel condensation product 4-(2-ethoxycarbonyl-2-cyanovinyl)-3,5-dimethyl-6-methylthio-1,1-dioxo-2-phenyl-2H-1,2-thiazine (2a). The 4-(2,2-dicyanovinyl)-3,5-dimethyl-6-methylthio-1, 1-dioxo-2-phenyl-2H-1,2-thiazine (2b) is obtained from 1 and malononitril. The masked 1,5-dicarbonyl compound 2a undergoes rind transformation to the 3-cyano-1,6-dimethyl-5-[1-methylthio-2-(N-phenylsulfamoyl)vinyl] pyridin-2-one (5) with methylamine. With ethanolic ethoxide the condensation products 2a,b afford the 7-amino-6-ethoxycarbonyl-4-methylthio-2,2-dioxo-1-phenyl-benzo[c]1,2-thiazine (6a), respectively the corresponding 6-cyano derivative 6b, while 3 cyclizises to furnish ethyl 2-amino-6-methyl-5-[1-methyl-2-methylthio-2-(N-phenyl-sulfamoyl)vinyl] nicotinate (4).