Catalytic Asymmetric Radical–Polar Crossover Hydroalkoxylation

Asymmetric intra­molecular
hydrofunctionalization of tertiary
allylic alcohols is described. This metal hydride-mediated catalytic
radical–polar crossover reaction delivers corresponding epoxides
in good to high enantio­selectivity and constitutes the first
example of asymmetric hydrogen atom transfer-initiated process. A
series of modified cobalt salen complexes has proven optimal for achieving
good efficiency and asymmetric induction. Experimental data suggest
that cationic cobalt complexes may be involved in the enantio­determining
step, where cation−π interactions in the catalyst contribute
to the asymmetric induction.