One-pot formal [3+3] cycloaddition of isocyanoacetates with in situ-derived azoalkenes for the synthesis of 1,4-dihydropyrimidine derivatives

The first conjugate addition of alpha-isocyanoacetates with in situ generated azoalkenes from alpha-halogeno hydrazones in the presence of Cs2CO3 has been developed. The reaction condition was suitable to various alpha-aryl substituted isocyanoacetates as well as aryl and alkyl-substituted alpha-halogeno hydrazones, affording the corresponding products in good to high yields. The adducts can be easily transformed into biologically attractive 1,4-dihydropyrimidine derivatives via an intramolecular cyclization by treating with AgOAc. The one-pot conjugate addition/intramolecular cyclization has also been investigated to furnish the formal [3 + 3] cycloadduct, 1,4-dihydropyrimidine derivatives.(C) 2021 Elsevier Ltd. All rights reserved.