Reactive ketimino radical acceptors: intermolecular alkyl radical addition to imines with a phenolic hydroxyl group.
Intermolecular carbon radical addition to the carbon-nitrogen double bond of ketimines was studied. In the study on the reactivity of various aldimines, we found that the aldimine 7 having a phenolic hydroxyl group shows an excellent reactivity toward nucleophilic carbon radicals. A remarkable effect of phenolic hydroxyl group is assumed to be the stabilization of intermediate aminyl radical provided by a hydroxyl group. The screening of reactive ketimino acceptors showed that ketimines 15, 17, and 19 having a phenolic hydroxyl group exhibit excellent reactivities. The radical addition to ketimines 15, 17, and 19 took place regioselectively at the imino carbon to give the C-alkylated products without the formation of N-alkylated products. Enantioselective ethyl radical addition to ketimine 15 using chiral box ligand and Zn(OTf)2 gave the diethylated product 30 in 80% ee.
Graduate School of Pharmaceutical Sciences, Kyoto University, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan.
Hideto
H
Miyabe
Yousuke
Y
Yamaoka
Yoshiji
Y
Takemoto
D002244:Carbon / Q000737:chemistry; D005609:Free Radicals / Q000737:chemistry; D007097:Imines / Q000737:chemistry*; D009584:Nitrogen / Q000737:chemistry; D010636:Phenols / Q000737:chemistry; D013237:Stereoisomerism
D005609:Free Radicals; D007097:Imines; D010636:Phenols; D002244:Carbon; D009584:Nitrogen