Synthesis 2012; 44(22): 3453-3464
DOI: 10.1055/s-0032-1316800
paper
© Georg Thieme Verlag Stuttgart · New York

Synthesis of Functionalized Fused-Ring Heterocycles from Tautomers of 2-(Thiazole, Oxazole, Benzothiazole, and Benzoxazole)-1-phenylethenols and 1,3-Diacid Chlorides or N-(Chlorocarbonyl) Isocyanate

Hondamuni I. De Silva*
Department of Chemistry, Mississippi State University, Mississippi State, MS 39762, USA   Fax: +1(662)3251618   Email: [email protected]   Email: [email protected]
,
Sabornie Chatterjee
Department of Chemistry, Mississippi State University, Mississippi State, MS 39762, USA   Fax: +1(662)3251618   Email: [email protected]   Email: [email protected]
,
William P. Henry
Department of Chemistry, Mississippi State University, Mississippi State, MS 39762, USA   Fax: +1(662)3251618   Email: [email protected]   Email: [email protected]
,
Charles U. Pittman Jr.*
Department of Chemistry, Mississippi State University, Mississippi State, MS 39762, USA   Fax: +1(662)3251618   Email: [email protected]   Email: [email protected]
› Author Affiliations
Further Information

Publication History

Received: 15 August 2012

Accepted after revision: 18 September 2012

Publication Date:
17 October 2012 (online)


Abstract

2-Methylthiazole, 2,4,5-trimethylthiazole, 2,4,5-trimethyloxazole, 2-methylbenzothiazole, and 2-methylbenzoxazole were each reacted with benzoyl chloride in acetonitrile–triethylamine to generate (Z)-2-(heterocyclic)-1-phenylvinyl benzoates. Base hydrolysis of these vinyl benzoates formed (Z)-2-(heterocyclic)-1-phenylethenols, which exist in both keto and enol tautomeric forms. These tautomers were used as starting materials for fused-ring heterocycle syntheses. Reactions with 2,2-dialkyl-1,3-diacid chlorides in acetonitrile–triethylamine afforded their corresponding 5,6-ring-fused 8-benzoyl-6,6-dialkyl-6H-thiazolo-, 8-benzoyl-2,3,6,6-tetramethyl-6H-thiazolo-, 8-benzoyl-2,3,6,6-tetramethyl-6H-oxazolo-, 4-benzoyl-2,2-dimethyl-1H-benzo[4,5]thiazolo-, and 4-benzoyl-2,2-dimethyl-1H-benzo[4,5]oxazolo[3,2,-a]pyridinedione derivatives. The 5,6,6-tri-ring fused species, 10-benzoyl-7,8-dihydropyrano[2,3-d]thiazolo[3,2-a]pyridin-5(6H)-one, was formed in the reaction of the tautomers of (Z)-1-phenyl-2-(thiazol-2-yl)ethenol with cyclobutane-1,1-dicarbonyl dichloride via a ring expansion after­ 5,6-ring fusion. Functionalized 5,6-ring-fused 8-benzoyl-6H-thiazolo- and 8-benzoyl-6H-oxazolo[3,2-f]pyrimidine-5,7-diones, and 4-benzoyl-1H-benzo[4,5]thiazolo- and 4-benzoyl-1H-benzo[4,5]oxazolo[3,2-c]pyrimidine-1,3(2H)-diones were also synthesized by reacting the (Z)-2-(heterocyclic)-1-phenylethenol tautomers with N-chlorocarbonyl isocyanate in THF–triethylamine.

Supporting Information

 
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