Triethylborane-Induced Intermolecular Radical Addition to Ketimines

The intermolecular carbon radical addition to ketimines was investigated by using triethylborane as a radical initiator. The screening of reactive radical acceptors showed that pyruvic hydrazone 3 and isatin hydrazone 7 exhibit good reactivities toward nucleophilic alkyl radicals. The reaction of 3 and 7 proceeded effectively even under aqueous-medium reaction conditions. In the presence of BF₃·OEt₂, the radical addition to chiral ketimine 11 proceeded with good diastereoselectivities.