Entry to nitrogen-containing heterocycles by based-promoted heterocyclization on allenylamides of l-α-aminoacids
摘要:
Allenylamides of Boc-protected alpha-aminoacids easily gave in basic medium heterocyclic products arising from attack of the NH group on the inside C-C double bond of the 1,2-diene moiety, namely imidazolidinones, pyrazinones, and a pyrrole compound. The microwave-assisted heterocyclization occurred cleanly at C-beta of the allenyl group with formation of pyrazin-2-ones having an endo- or exocyclic double bond. (C) 2009 Elsevier Ltd. All rights reserved.
Palladium-Catalyzed Domino Carbopalladation/5-exo-Allylic Amination of α-Amino Allenamides: An Efficient Entry to Enantiopure Imidazolidinones
摘要:
Allenamides of alpha-amino acids were converted into enantiopure 2-vinylimidazolidin-4-ones by a carbopalladation/exo-cyclization process. The products were obtained in 2.5:1-5.5:1 dr, with 94-99% ee. The palladium-catalyzed carbonylative cyclization of the same substrates afforded enone structures. Starting from properly substituted allenamides, an intramolecular carbopalladation followed by intramolecular amination gave rise to tricyclic fused-ring imidazolidinones.