Synthesis and reactions of furocondensed derivatives

Abstract

This paper describes the preparation of furo[2',3' :4,5]pyrollo[1,2-d]-1,2,4-triazolo[3,4-f]-1,2,4-triazines (V) from 4H-furo[3,2-b]pyrolle-5-carboxhydrazide (I, and benzo[b]furo[2',3' :4,5]-pyrrolo[1,2-d]-1,2,4-triazolo[3,4-f]-1,2,4-triazines (VIII) from 1H-benzo[b]furo[3,2-b]pyrrole-2-carboxhydrazide. Compound I reacts with triethyl orthoformate or orthoacetate to give 1,2-dihydro[2',3'-4,5]pyrrolo[1,2-d]-1,2,4-triazin-1-one or its methyl analogue II. Compounds of general formula II afford with phosphorus pentasulfide thiones III; III yields IV with hydrazine. Cyclization of IVwith triethyl orthoformate or orthoacetate furnished compounds V. Similarly, VIgives with hydrazine VII, which, upon reaction with triethyl orthoformate or orthoacetate affords VIII.