No abstract

A general AzePhenol dinuclear zinc catalytic system has been successfully developed and applied into the asymmetric Michael addition of 4-hydroxyl pyrones and 4-hydroxycoumarins to β,γ-unsaturated α-keto esters. Excellent yields (up to 99%) and high enantioselectivities (up to 94% ee) are obtained for a wide range of substrates under mild conditions in the absence of additives. This bimetallic catalytic approach represents a new and effective asymmetric synthetic protocol to access a variety of bioactive compounds with pharmacological interest. The possible mechanism is proposed to explain the origin of the asymmetric induction.

An efficient approach to saccharin-fused 1,4-DHPs has been established by using a [3 + 3] annulation process. The chemical event was enabled by a Et 3 N-catalyzed tandem Michael/aza-Pinner reaction of alkyl cyclic N-sulfonyl ketimines as nucleophiles with α,α-dicyanoolefins. Under mild conditions, the desired products were readily prepared in good to excellent yields and with broad functional group tolerance (up to 95 % yield, 29 examples). Notably, this practical methodology features the synthesis of pentacyclic spirooxindoles bearing a quaternary spiro-stereocenter.[a] Z.