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■ Synthesis of 6,7-Dihydropyrido[2,3-d]pyrimidin-5(8H)-one Derivatives Based on the Reaction of 1-(4-Chloropyrimidin-5-yl)alk-2-en-1-one Derivatives with Primary Amines

Kazuhiro Kobayashi,* Ryoga Ono, Kouki Ishitobi, Yuuki Chikazawa, Hidetaka Hiyoshi, and Kazuto Umezu

*Division of Applied Chemistry, Department of Chemistry and Biotechnology, Graduate School of Engineering, Tottori University, 4-101 Koyama-minami, Tottori 680-8552, Japan

Abstract

A convenient sequence for the synthesis of 6,7-dihydropyrido[2,3-d]pyrimidin-5(8H)-one derivatives has been developed. Thus, treatment of 4-chloro-6-methoxy-2-(methylsulfanyl)pyrimidine with lithium diisopropylamide (LDA) generates 4-chloro-5-lithio-6-methoxy-2- (methylsulfanyl)pyrimidine, which are allowed to react with α,β-unsaturated aldehydes to give the corresponding 1-(4-chloropyrimidin-5-yl)alk-2-en-1-ol derivatives. Oxidation of these alkenols with activated manganese(IV) oxide provides 1-(4-chloropyrimidin-5-yl)alk-2-en-1-one derivatives, of which reaction with a variety of primary amines constitutes tetrahydropyridinone structure to give the desired products.