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Synthesis of Pyrimidoquinolines via the Pictet-Spengler Reaction
P. K. Agarwal, S. K. Sharma, D. Sawant, B. Kundu*
Central Drug Research Institute, Lucknow, India
23 March 2009 (online)
Reported is the first use of a pyrimidine ring as the π-nucleophilic component in the Pictet-Spengler reaction. The starting materials, 2-amino-4-substituted pyrimidines, or 2-amino-4,6-disubstituted pyrimidines were prepared via a 2-4-step sequence starting from 3-dimethyl-amino-1-(2-nitrophenyl)-propenone. The Pictet-Spengler reaction proceeds in moderate to good yields, tolerating EWGs and EDGs on the aldehyde reactant. 4,6-Disubstituted pyrimidines afforded slightly lower yields than 4-monosubstituted analogues, failing in two cases of 2-substituted aryl aldehydes which may be due to a steric R²,R³ effect. Attempted reaction with a pyridine subunit instead of a pyrimidine failed.