Electrochemical Cross-Dehydrogenative Coupling of Isochroman and Unactivated Ketones.

An unprecedented electrochemical cross-dehydrogenative coupling reaction between isochroman and unactivated ketones to directly synthesize α-substituted isochromans has been developed. This strategy provides a facile and efficient procedure to the direct activation of C(sp3)-H bond adjacent to the O atom of isochroman. The method features high atom economy, chemical oxidant-free, and mild conditions, in which methanesulfonic acid (MsOH) acts as both electrolyte and catalyst, making the process more convenient and environmentally friendly. Gram-scale experiment and synthesis of antitumor active compounds demonstrate the great potential of this protocol for practical applications.

Merging the Non-Natural Catalytic Activity of Lipase and Electrosynthesis: Asymmetric Oxidative Cross-Coupling of Secondary Amines with Ketones.

We describe the enantioselective oxidative cross-coupling of secondary amines with ketones by combining the non-natural catalytic activity of lipase with electrosynthesis. Various 2,2-disubstituted 3-carbonyl indoles with a stereogenic quaternary carbon center were synthesized from 2-substituted indoles in yields up to 78 % with good enantio- and diastereoselectivities (up to 96 : 4 e.r. and >20 : 1 d.r.). This unprecedented protocol demonstrated that hydrolase catalysis is compatible with electrosynthesis, and the reaction can be carried out in organic solvents with a broad substrate scope and good stereoselectivity. This work provides insights into enzymatic electrosynthesis.

Asymmetric oxidative Mannich reactions promoted by photocatalysis and electrochemistry.

The asymmetric Mannich reaction is an essential method in contemporary organic chemistry. As a representative of clean and green synthesis methods, photochemical and electrochemical oxidation strategies have re-emerged in recent years, providing new ideas for asymmetric Mannich reactions. Numerous chiral ß-amino carbonyl compounds have been accessed in satisfactory yields with excellent enantioselectivity via such novel asymmetric oxidative Mannich reactions. This minireview highlights plentiful advances in asymmetric oxidative Mannich reactions that rely on photoredox or anodic-oxidation and covers the literature from 2014 to date. Furthermore, the future development of this field is envisaged.