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Synthesis 2006(24): 4180-4186  
DOI: 10.1055/s-2006-950364
PAPER
© Georg Thieme Verlag Stuttgart · New York

New Efficient Synthesis of 2-Substituted Benzothieno[3,2-d]pyrimidin-4(3H)-ones via a Tandem Aza-Wittig Reaction

Sheng-Zhen Xu, Yang-Gen Hu, Ming-Wu Ding*
Key Laboratory of Pesticide & Chemical Biology of Ministry of Education, College of Chemistry, Central China Normal University, Wuhan 430079, P. R. of China
Fax: 86(27)67862041; e-Mail: mwding@mail.ccnu.edu.cn;
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Received 5 July 2006
Publikationsdatum:
13. November 2006 (online)

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Abstract

1-Aryl-3-[2-(ethoxycarbonyl)benzothien-3-yl]carbodiimides 4, obtained from aza-Wittig reactions of iminophosphorane 3 with aryl isocyanates, reacted with secondary amines, phenols, or alkanols in the presence of a catalytic amount of potassium carbonate or sodium alkoxide to give 2-substituted benzothieno[3,2-d]pyrimidin-4(3H)-ones 6 in good yields. The reaction of carbodiimides 4 with primary amines RNH2 (R ≠ H, Me) in the presence of sodium ethoxide selectively produced one regioisomer 8 via a base-catalyzed cyclization mechanism. However, a different regioisomer 9 was obtained when primary amines RNH2 (R = H, Me) were used in the absence of sodium ethoxide via a direct cyclization mechanism.

Key words

benzothieno[3,2-d]pyrimidin-4(3H)-one - iminophosphorane - carbodiimide - aza-Wittig reaction - synthesis