N-Heterocyclic Carbene Catalyzed [3+2] Cycloaddition of Enals with Masked Cinnamates for the Asymmetric One-Pot Synthesis of Adipic Acid Derivatives

Cu-Catalyzed Asymmetric Dicarboxylation of 1,3-Dienes with CO2

Dicarboxylic acids and derivatives are important building blocks in organic synthesis, biochemistry, and the polymer industry. Although catalytic dicarboxylation with CO2 represents a straightforward and sustainable route to dicarboxylic acids, it is still highly challenging and limited to generation of achiral or racemic dicarboxylic acids. To date, catalytic asymmetric dicarboxylation with CO2 to give chiral dicarboxylic acids has not been reported. Herein, we report the first asymmetric dicarboxylation of 1,3-dienes with CO2 via Cu catalysis. This strategy provides an efficient and environmentally benign route to chiral dicarboxylic acids with high regio-, chemo-, and enantioselectivities. The copper self-relay catalysis, that is, Cu-catalyzed boracarboxylation of 1,3-dienes to give carboxylated allyl boronic ester intermediates and subsequent carboxylation of C-B bonds to give dicarboxylates, is key to the success of this dicarboxylation. Moreover, this protocol exhibits broad substrate scope, good functional group tolerance, easy product derivatizations, and facile synthesis of chiral liquid crystalline polyester and drug-like scaffolds.

Recent advances of N-heterocyclic carbenes in the applications of constructing carbo- and heterocyclic frameworks with potential biological activity

In recent years, N-heterocyclic carbenes (NHCs) have established themselves as a masterful and promising type of organocatalyst for the speedy construction of medicinally and biologically significant molecules from common and accessible small molecules. In particular, various cyclic scaffolds, including carbocycles and heterocycles, have been synthesized using NHCs via cycloaddition reaction. An exhaustive review focused on the chemistry of NHCs in these cyclic molecules has yet to be reported. In this contribution, a general picture of the utilization of NHCs in constructing twelve kinds of bioactive cyclic skeletons is firstly presented. We provide a systematic and comprehensive overview from the perspective of cycloaddition reactions; moreover, the limitations, challenges, and future prospects were discussed.

A radical [3 + 2]-cycloaddition reaction for the synthesis of difluorocyclopentanones

Described herein is a novel radical-mediated [3 + 2]-cycloaddition reaction of alkenes to afford difluorocyclopentanones.

NHC-Catalyzed Cascade Reaction between β-Methyl Enals and Dienones for Quick Construction of Complex Multicyclic Lactones

A NHC-promoted cascade reaction between β-methyl enal and dienone is developed for quick access to multicyclic lactone molecules bearing quaternary chiral carbon centers. Our study constitutes the first 1,6-addition of the acylazolium vinyl enolate γ-carbon via NHC catalysis and provides rapid access to complex lactone molecules that are otherwise difficult to prepare. The structurally sophisticated lactone products bearing up to four fused ring structures are afforded in up to quantitative yields with good to excellent enantioselectivities.

Highly enantioselective 1,6-addition of dienolates to coumarins and chromones through N-heterocyclic carbene catalysis

An efficient protocol employing NHC-organocatalysis in asymmetric γ,δ-difunctionalization of cyanocoumarins and nitrochromones via a 1,6-addition of dienolates is established.

Asymmetric synthesis of cyclopentanones through dual Lewis acid-catalysed [3+2]-cycloaddition of donor–acceptor cyclopropanes with ketenes

A dual Lewis acid system promotes the formal [3+2]-cycloaddition of enantioenriched donor–acceptor cyclopropanes with ketenes to afford cyclopentanones.