Metallocarbenes as Substituents in 8-Electron Electrocyclizations

Density functional theory was used to elucidate the mechanism and the pericyclicity of chromium-catalyzed bicyclization reactions that purportedly involve 8-electron electrocyclization steps. Our computational results indicate that these reactions do indeed proceed via 8-electron electrocyclization rather than an alternative pathway involving 4-electron electrocyclization followed by Cope rearrangement. The role of C=[M] groups on the electrocyclization, specifically its pericyclicity, was examined in detail using modern theoretical tools. The mechanism and the pericyclicity of metal-promoted bicyclization reactions that purportedly involve 8-electron electrocyclization steps were examined computationally, with results showing that these reactions do indeed proceed via 8-electron electrocyclizations rather than alternative pathways involving 4-electron electrocyclizations followed by Cope rearrangements.image