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Paper | Special issue | Vol 73, No. 1, 2007, pp.777-793
Published online, 7th September, 2007
DOI: 10.3987/COM-07-S(U)58
Synthesis of Thieno[3,2-e][1,2,4]triazolo[1,5-c]pyrimidin-5(6H)-ones via Their [1,2,4]Triazolo[4,3-c]pyrimidine Compounds as New Ring Systems by Dimroth-Type Rearrangement

Tomohisa Nagamatsu,* Shoeb Ahmed, Abugafar M. L. Hossion, and Seiji Ohno

*Department of Drug Discovery and Development, Division of Pharmaceutical Sciences, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, 1-1-1, Tsushima-naka, Okayama 700-8530, Japan

Abstract

General and facile syntheses of thieno[3,2-e][1,2,4]triazolo[1,5-c]pyrimidin-5(6H)-one (6a) and its 2-substituted derivatives (6b-j) produced by instantaneous isomerization of their [4,3-c] compounds (7a-j), which were prepared by condensation of 4-hydrazinothieno[2,3-d]pyrimidin-2(1H)-one (10) with appropriate triethyl orthoesters or by oxidative cyclization of 4-(benzylidenehydrazino)thieno[2,3-d]pyrimidin-2(1H)-ones (11c-j), are described as novel ring systems and as a new class of potential xanthine oxidase inhibitors. The [1,5-c] isomers (6a-c) were further prepared by condensation of 3-amino-4-imino-2-oxo-1,2,3,4-tetrahydrothieno[2,3-d]pyrimidine (14) with appropriate triethyl orthoesters as a synthetic method for a reliable structure of the tricyclic ring systems.