Efficient Preparation of β-Branched γ,δ-Unsaturated Esters through Copper-Catalyzed Allylic Alkylation of Ketene Silyl Acetal

Abstract

Copper-catalyzed allylic alkylation of ketene silyl acetals proceeded with excellent γ-E-selectivity. Efficient α-to-γ chirality transfer with anti-selectivity occurred in the reaction of enantioenriched secondary allylic phosphates, affording enantioenriched β-branched γ,δ-unsaturated esters. The reaction was readily scalable and highly reliable in terms of product yield and stereoselectivities.

Key words

γ,δ-unsaturated esters - copper - allylic alkylation - ketene silyl acetal - regioselectivity

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3

The regioselectivity in palladium-catalyzed allylic substitutions that involve a (π-allyl)palladium intermediates is highly dependent on the substitution pattern of allylic substrates. See refs 1 and 2a-i.

16

See the Supporting Information of ref. 6 for procedures