Catalysis of Radical Cyclizations from Alkyl Iodides under H2: Evidence for Electron Transfer from [CpV(CO)3H]-

Radical cydizations are most often achieved with Bu3SnH in the presence of a radical initiator, but environmental considerations demand that alternative reagents be developed-ones that can serve as a synthetic equivalent to the hydrogen atom. We have revisited [CpV(CO)(3)H](-), a known replacement for Bu3SnH, and found that it can be used catalytically under H-2 in the presence of a base. We have carried out tin-free catalytic radical cydizations of alkyl iodide substrates. The reactions are atom -efficient, and the conditions are mild, with broad tolerance for functional groups. We have, for example, achieved the first 5-exo radical cyclization involving attack onto a vinyl chloride. We suggest that the radicals are generated by an initial electron transfer.