Dihydropyrimidines (DPs) show a wide range of biological activities suitable for medicinal applications. Among DP derivatives, 2-aryl-DPs have been reported to display remarkable pharmacological properties. In this work, we describe a method of synthesizing hitherto unavailable fully substituted pentasubstituted 2-aryl-DPs as tautomeric mixture using a Pd(PPh3)4-catalyzed/CuBr-mediated 2-arylation reaction. The reaction using aryl tributylstannanes with various substituents such as MeO, Me, Ph, CF3, CO2Me, and NO2 groups efficiently afforded the corresponding 2-aryl-DPs in high yields. Heteroaryl tributylstannanes having 2-thienyl, 3-thienyl, or 2-pyridinyl groups were also suitable for the reaction. Regarding the substituents at the 4-, 5-, and 6-positions of DPs, the reactions of DPs bearing substituents such as Me, n-C3H7, n-C5H11, -(CH2)5- , phenyl and fluorenylidene groups proceeded smoothly to give the desired products. The synthetic method was also applied to a 2-thioxo-DP to give the 2-aryl-DP. Therefore, the reaction will help expand DP-based molecular diversity, which may impact biological and pharmacological studies.
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