Diacetylketene N,S-acetals in synthesis of new functionalized 2(1H)- pyrimidinethiones
Vladimir Dorokhov,* Alexander Komkov, and Sergey Baranin
N.D.Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences,
47 Leninsky prosp., 119991 Moscow, Russian Federation
E-mail:
[email protected]
Dedicated to Professor Branko Stanovnik on the occasion of his 65th birthday
(received 25 July 03; accepted 15 Dec 03; published on the web 29 Dec 03)
Abstract
New 5-acetyl-4-alkylthio-6-methyl-2(1H)-pyrimidinethiones were prepared from diacetylketene N,S-acetals and isothiocyanates. They were converted into 4-amino derivatives, which can be applied for the construction of functionalized pyrido[2,3-d]pyrimidines and pyrimido[4,5- d]pyrimidines.
Keywords: Diacetylketene N,S-acetals, isothiocyanates, heterocyclization, 2(1H)-pyrimidine- thiones, pyrimido[4,5-d]pyrimidines, pyrido[2,3-d]pyrimidines
Introduction
Ketene N,S-acetals are known to be useful reagents in heterocyclic synthesis.1,2 Among these, particular attention has been given to oxoketene N,S-acetals as functionalized enaminones.3,4
Previously we reported a convenient procedure for the preparation of N-unsubstituted diacylketene N,S-acetals from ß-diketones and alkyl thiocyanates in the presence of Ni(acac)2.5 These compounds were shown to be suitable starting materials for synthesizing 4-acetyl-5- aminopyrazoles,6 pyrazolo[3,4-d]pyrimidines,6 functionalized 2(1H)pyrimidinones,7 and 3- cyano-4-pyridones.8 In continuation of our work on the synthetic utility of dioxoketene N,S- acetals, we describe the synthesis of functionalized 2-pyrimidinethiones from diacetylketene N,S-acetals and isothiocyanates. Although 2-pyrimidinethiones have been extensively investigated and different approaches to their preparation have been developed,9 new methods for the synthesis of 2-pyrimidinethiones carrying functional groups in the 5- and 6-positions are desirable, since compounds of this type may be used for constructing fused pyrimidines.
Monoaroylketene N,S-acetals are reported to react with benzoyl isothiocyanate as C- nucleophiles to give the corresponding adducts which undergo cyclization into 4-pyrimidine-
