Abstract
Vilsmeier reactions of ethyl 2-benzimidazoleacetate (4), ethyl 2-benzothiazoleacetate (5), and ethyl 2-benzoxazoleacetate (6) gave ethyl α-(dimethylaminomethylene)-2-benzimidazoleacetate (7), ethyl α-(dimethylaminomethylene)-2-benzothiazoleacetate (8), and ethyl α-(dimethylaminomethylene)-2-benzoxazoleacetate (9), respectively. Reaction of the enamines (7, 8 and 9) with diketene, acetic anhydride, propionic anhydride, and active methylene compounds such as ethyl cyanoacetate and malononitrile gave rise to the corresponding pyrido [2, 1-b] benzoazoles (10-19).
