Cp2TiPh-coordinated cyano and ester groups as efficient ketyl radical acceptors in the reductive radical cyclization of γ- and δ-cyano ketones and δ-keto esters

Cp2TiPh promotes the reductive radical cyclization of γ- and δ-cyano ketones and δ-keto esters to give α-hydroxycycloalkanones in moderate to good yields; the titanium reagent coordinates to both the ketone and the cyano or ester terminus, the LUMO of the cyano or ester group is thus lowered, and cyclization proceeds irreversibly without formation of the unstable iminyl or alkoxy radical intermediates.