Racemic hemiacetals as oxygen-centered pronucleophiles triggering cascade 1,4-addition/Michael reaction through dynamic kinetic resolution under iminium catalysis. Development and mechanistic insights

Synergistic zinc catalyst mediated oxa-Michael kinetic resolution reaction

An oxa-Michael kinetic resolution reaction is developed to efficiently construct complexed polycyclic motifs by developing novel bifunctional zinc catalysts.

Recent advances in organocatalytic asymmetric oxa-Michael addition triggered cascade reactions

In this review, we summarized recent advances in organocatalytic asymmetric oxa-Michael addition triggered cascade reactions.

Stereoconvergent Conjugate Addition of Arylboronic Acids to α-Angelica Lactone Derivatives: Synthesis of Stereochemically Complex γ-Butyrolactones

Catalyzed stereoconvergent 1,4-additions to unsaturated carbonyls are rare but of high potential value. This letter details the development of enantioselective arylation reactions of boronic acids and β,γ-butenolides. These reactions are catalyzed by commercially available hydroxy[(S)-BINAP]-rhodium(I) dimer to afford stereochemically complex γ-butyrolactone derivatives. The reaction products provide functionality amenable to further manipulation and can lead to products with up to three contiguous stereocenters. The reaction proceeds under a dynamic kinetic resolution manifold by isomerizing the achiral starting material into an interconverting mixture of enantiomeric conjugate acceptors, followed by catalyst-controlled, enantiomer-selective 1,4-addition. Base-promoted racemization of the intermediate α,β-butenolide is possible due to the high kinetic and thermodynamic acidity of the γ-proton.

Synergistic Catalysis: Highly Enantioselective Cascade Reaction for the Synthesis of Dihydroacridines

The first stereoselective synthesis of dihydroacridines through synergistic catalysis, achieving the final target compounds with good to excellent yields and good to excellent enantioselectivities and diastereoselectivities, is reported. The synergistic approach consists in the activation of substituted quinolines with a Lewis acid catalyst that react in a cascade fashion with activated enals in the iminium form. Mechanistic calculations support a consecutive Michael-aldol reaction, followed by dehydration.

Synergistic catalysis: enantioselective cyclopropanation of alkylidene benzoxazoles by Pd(ii) and secondary amine catalysis. Scope, limitations and mechanistic insight

An enantioselective synergistic cascade cyclopropanation/NHC catalyzed ring opening has been reported. DFT calculations have been performed to confirm the mechanism.