Construction of quaternary carbon centers by using substitution of γ,γ-disubstituted secondary allylic picolinates with alkylcopper reagents

ZnI2 was found to promote regio- and stereoselective substitution of γ,γ-disubstituted secondary allylic picolinates with alkylcopper reagents derived from alkyl-MgBr and CuBr·Me2S in a 2:1 ratio to furnish quaternary carbon centers in good yields. Alkyl groups delivered efficiently were the primary, secondary, and benzyl classes such as Me, Et, Bu, C16H33, Ph(CH2)2, Ph(CH2)3, c-C6H11, and Bn. As an application, allylic picolinates with the (E)- or (Z)-olefin afforded quaternary carbon centers that are the enantiomers of each other.

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