Cobalt(I)-catalyzed [6π+2π]-cycloaddition of allenes to N-carbethoxy(phenoxy)azepines for the synthesis of 9-azabicyclo[4.2.1]nona-2,4-dienes

Abstract

The [6π+2π]-cycloaddition of allenes to N-carbethoxyazepine or N-carbophenoxyazepine catalyzed by the Co(acac)2(dppe)/Zn/ZnI2 system was performed for the first time and gave previously unknown substituted 9-azabicyclo[4.2.1]nona-2,4-dienes and 16-azatricyclo[9.4.1.02,10]hexadeca-2,12,14-trienes in 75–95% yields. The structures of the resulting azacyclic compounds were reliably proved using NMR spectroscopy and X-ray diffraction analysis. The obtained 9-azabicyclo[4.2.1]nona-2,4-dienes and 16-azatricyclo[9.4.1.02,10]hexadeca-2,12,14-trienes showed high antitumor activities in vitro against Jurkat, K562, U937 and HL60 cancer cell lines.