Bimetallic Catalytic Asymmetric Tandem Reaction of β‐Alkynyl Ketones to Synthesize 6,6‐Spiroketals

Golden catalysis: The enantioselective tandem reaction of β,γ‐unsaturated α‐ketoesters with β‐alkynyl ketones was achieved by using bimetallic Au^ΙΙΙ/chiral N,N′‐dioxide‐Mg^ΙΙ catalyst. The enantioriched and multifunctional 6,6‐spiroketals with three stereocenters were obtained.

Abstract

The enantioselective tandem reaction of β,γ‐unsaturated α‐ketoesters with β‐alkynyl ketones was realized by a bimetallic catalytic system of achiral Au^ΙΙΙ salt and chiral N,N′‐dioxide‐Mg^ΙΙ complex. The cycloisomerization of β‐alkynyl ketone and asymmetric intermolecular [4+2] cycloaddition with β,γ‐unsaturated α‐ketoesters subsequently occurred, providing an efficient and straightforward access to chiral multifunctional 6,6‐spiroketals in up to 97 % yield, 94 % ee and >19/1 d.r. Besides, a catalytic cycle was proposed based on the results of control experiments.

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