Ring cleavage of dihydropyrimidine skeleton

Hidetsura Cho, Eunsang Kwon, Yoshizumi Yasui, Satoshi Kobayashi, Shin Ichiro Yoshida, Yoshio Nishimura, Masahiko Yamaguchi

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13 Citations (Scopus)


The first observation of ring cleavage between positions 1 and 2 of a 1,4-dihydropyrimidine skeleton was reported upon the nucleophilic addition of 4,6-unsubstituted 1,4-dihydropyrimidine with 3 equiv of an aniline derivative or phenylhydrazine in the presence of 0.1 equiv of pyridinium p-toluenesulfonate (PPTS) in CH2Cl2; the nucleophilic reactions of 4-methyl-6-unsubstituted 1,6(3,4)-dihydropyrimidine with the same amines gave conventional substituted products at position 2. The effect of this ring opening was found to be due to the electron density of the benzene ring of a nucleophilic amine. On the other hand, aralkylamines, alkylamines, or heterocyclic amines did not cleave the skeleton. The ring-opening chemical structure was confirmed by X-ray crystallographic analysis. This characteristically different phenomenon may be due to the pattern of two CC double bonds of 1,4-DP and 1,6(3,4)-DP as well as to the effect of two substituted groups on the DP ring.

Original languageEnglish
Pages (from-to)7185-7188
Number of pages4
JournalTetrahedron Letters
Issue number52
Publication statusPublished - 2011 Dec 28


  • Dihydropyrimidine
  • Dihydropyrimidine skeleton
  • Ring cleavage
  • Ring opening


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