An unprecedented hydrogen atom transfer-triggered intramolecular cascade reaction between alkenes and enones is developed, using Fe(acac)3, PhSiH2(Oi-Pr) and trimethyl borate, to efficiently construct cis-fused bicyclic cyclopropanols, privileged scaffolds often found in natural products. This mild protocol features unique regio- and stereo-selectivity and impressive functional group tolerability. Mechanistic studies reveal that cyclopropane-containing motifs could be generated through a stepwise radical process rather than the Michael addition reaction.
