Synthesis of Pyrido[2,3-d]pyrimidines Catalyzed by 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ)/tert-Butyl Nitrite (TBN)/O2

Abstract

Catalyzed by 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ)/tert-butyl nitrite (TBN)/O2, an efficient tandem oxidative reaction of uracils/thiouracil with 1,3-diarylpropenes is disclosed. It undergoes oxidative coupling, intramolecular cyclization, and dehydro-aromatization to provide multi-substituted pyrido[2,3-d]pyrimidines/thiopyrido[2,3-d]pyrimidines in moderate to excellent yields. It has the advantages of high atom economy, green terminal oxidant, and metal-free conditions.