Synthesis and antimicrobial activities of 2-substituted 12H-chromeno[3,2-e][1,2,4]triazolo[1,5-c]pyrimidines, 3-ethoxycarbonyl-12H-chromeno[3,2-e][1,2,4]triazolo[1,5-c] pyrimidine-2-one and ethyl 2-formylamino- and 2-acetylamino-4H-chromene-3-carboxylates