Copper-catalyzed asymmetric 1,6-conjugate addition of in situ generated para -quinone methides with β-ketoesters.

A Cu-catalyzed asymmetric 1,6-conjugate addition of in situ generated para -quinone methides ( p -QMs) with β-ketoester has been developed to construct a ketoester skeleton bearing an adjacent tertiary-quaternary carbon stereocenter in good yields and high enantioselectivities. This is the first example of metal-catalyzed asymmetric transformations of the in situ generated p -QMs, avoiding using pre-synthesized p -QMs requiring bulky 2,6-substitutions and highlighting a new dual catalytic activation with the chiral bis(oxazoline)-metal complex acting as a normal Lewis acid to activate the β-ketoesters and a source of Brønsted acid responsible for generating the p -QMs in situ .