Asymmetric oxidative Mannich reactions promoted by photocatalysis and electrochemistry

Electrochemically Promoted Three-Component Reaction to N-Sulfonyl Amidines

In this study, a multicomponent reaction via the Mannich intermediate was developed using methanol, secondary amine, and sulfonamide as starting materials. This method uses methanol as a green C1 source. The substrate scope is wide, and the yield is good. The mechanistic study shows that methanol generates formaldehyde under electrochemical conditions, and sulfonyl amidine as a nucleophile reacts with Schiff base intermediates to form N-sulfonyl amidine in a single step.

Electroreductive Hydroxymethylation of Imines with Ketones To Access β-Amino Alcohols

In this article, an electrochemical method for the direct synthesis of β-amino alcohols from imines and ketones is described. Mechanistic studies, including a radical trapping experiment, electron paramagnetic resonance, cyclic voltammetry, and divided-cell electrolysis experiment, support the radical-involved reductive cross coupling of imines with ketones at the cathode. The use of abundant and easily prepared starting materials, high atom- and step-economy, and insensitivity to air and moisture make this synthetic strategy more efficient for the construction of various β-amino alcohol derivatives.

Electricity-driven asymmetric bromocyclization enabled by chiral phosphate anion phase-transfer catalysis

Electricity-driven asymmetric catalysis is an emerging powerful tool in organic synthesis. However, asymmetric induction so far has mainly relied on forming strong bonds with a chiral catalyst. Asymmetry induced by weak interactions with a chiral catalyst in an electrochemical medium remains challenging due to compatibility issues related to solvent polarity, electrolyte interference, etc. Enabled by a properly designed phase-transfer strategy, here we have achieved two efficient electricity-driven catalytic asymmetric bromocyclization processes induced by weak ion-pairing interaction. The combined use of a phase-transfer catalyst and a chiral phosphate catalyst, together with NaBr as the bromine source, constitutes the key advantages over the conventional chemical oxidation approach. Synergy over multiple events, including anodic oxidation, ion exchange, phase transfer, asymmetric bromination, and inhibition of Br₂ decomposition by NaHCO₃, proved critical to the success.

Cooperative photocatalysis and l-/d-proline catalysis enables enantioselective oxidative cross-dehydrogenative coupling of acyclic benzylic secondary amines with ketones

We developed an enantioselective cross-dehydrogenative coupling of acyclic benzylic secondary amines with ketones by combining photocatalysis and l-/d-proline catalysis.

The effect of N-vacancy on the photocatalytic activity of graphitic carbon nitride in the oxidative Mannich reaction

N-vacancy g-CN was used in Mannich oxidative reaction as a photocatalyst, having mid-gap states that enhance reaction kinetics. This facile photocatalyst enabled successful formation of challenging THIQ with EWG and chemo-selectivity on C–C bond.

Direct Reductive Arylation of Imines with Electron-Deficient (Hetero) Arenes via Electrosynthesis to Access Benzylic Amines

In this paper, a direct access to benzylic amines from imines and electron-deficient (hetero) arenes via electrochemical radical-radical cross-coupling is described. The reaction has the characteristics of the wide range of substrates, excellent functional group tolerance, metal-free and highly atom-economical. The insensitivity to air and moisture makes this synthetic strategy more efficient for the construction of various benzylic amine derivatives.