THE FIRST AND RELIABLE SYNTHESIS OF THIENO[2,3-e][1,2,4]-TRIAZOLO[l,5-c]PYRIMIDIN-5(6H)-ONES VIA THEIR [4,3-c] COMPOUNDS BY DIMROTH REARRANGEMENT

摘要

This paper describes a reliable and general synthesis of thieno[2,3-e]-[1,2,4]triazolo[1,5-c]pyrimidin-5(6H)-one (5a) and its 2-substituted derivatives (5b-i) as a novel ring system prepared by nimble isomerization of their [4,3-c] compounds (4a-i),which were produced by condensation of 4-hydrazinothieno-[3,2-d]pyrimidin-2(lH)-one (12) with appropriate triethyl orthoesters or by oxidative cyclization of 4-(benzylidenehydrazino)thieno[3,2-d]pyrimidin-2(1H)-ones (13c-i).The [1,5-c] isomers (5a-c) were further prepared by condensation of 3-amino-4-imino-2-oxo-l,2,3,4-tetrahydrothieno[3,2-d]pyrimidine (16) with appropriate triethyl orthoesters as a synthetic method for a reliable structure of the tricyclic ring systems.