Mannich condensations of activated cyclic enamines

Abstract

The synthesis of Mannich compounds starting from activated enamines, i.e., 2-nitromethylene-pyrrolidine and pyrrolidin-2-ylidene-acetic acid ethyl ester, with various amines and formaldehyde or ethyl glyoxylate are described. In order to furnish new Mannich type molecules and to improve the yields sequential reaction routes and 1,2,3-benzotriazole-substituted adducts as reactants were also tested. Additionally, the steric structure of a tricyclic spiro compound formed unexpectedly in high yield was elucidated in details by modern NMR methods.

Graphical Abstract

Keywords:

• Benzotriazole auxiliary
• Mannich reaction
• one pot reactions
• push–pull alkenes
• pyrrolopyrimidines

Acknowledgments

The PhD scholarship from Szent István University to A. Alekszi-Kaszás is gratefully acknowledged. We are grateful to Dr M. Dékány, Gedeon Richter Plc., Spectroscopic Research Department, for the high-resolution MS measurements.