Cyclobutene ring-opening of bicyclo[4.2.0]octa-1,6-dienes: access to CF3-substituted 5,6,7,8-tetrahydro-1,7-naphthyridines.

An efficient method for the synthesis of novel CF(3)-substituted tetrahydro-1,7-naphthyridines including cyclic α-amino acid derivatives has been developed. The method is based on unusual cyclobutene ring-opening of bicyclo[4.2.0]octa-1,6-dienes with pyrrolidine to afford the corresponding 1,5-diketones followed by their heterocyclization. A convenient one-pot procedure has been also elaborated starting from readily available trifluoromethylated 1,6-allenynes.