Visible Light-Induced Regioselective Intermolecular [2 + 2]-Cycloaddition of Alkyne and 2(1H)-Quinolone Derivatives.

We have developed a visible light-induced intermolecular [2 + 2]-cycloaddition reaction between alkenes and alkynes using thioxanthone and Cu(OTf)2 as cocatalysts. Various quinolin-2(1H)-ones, featuring diverse substituted groups, were successfully employed in this reaction, resulting in the synthesis of a series of 4,8b-dihydrocyclobuta[c]quinolin-3(2aH)-ones. Our methodology presents a novel synthetic approach for alkene-alkyne [2 + 2]-cycloaddition, delivering cyclobutene derivatives with exceptional regioselectivity.

An NHC-catalyzed [3+2] cyclization of ß-disubstituted enals with benzoyl cyanides.

The NHC-catalyzed asymmetric [3+2] cyclization of benzoyl cyanides to homoenolate generated in situ from enals was reported. This methodology leads to the efficient construction of a series of chiral cyclic compounds bearing vicinal quaternary stereocenters under mild reaction conditions. Additionally, the representative large-scale and derivatization reactions of the chiral cyclic products reveal the potential synthetic utility of this protocol.

Progress in the Electrochemical Reactions of Sulfonyl Compounds.

Electrosynthesis has recently attracted more and more attention due to its great potential to replace chemical oxidants or reductants in molecule-electrode electron transfer. Sulfonyl compounds such as sulfonyl hydrazides, sulfinic acids (and their salts), sulfonyl halides have been discovered as practical precursors of several radicals. As electrochemical redox reactions can provide green and efficient pathways for the activation of sulfonyl compounds, studies for electrosynthesis have rapidly increased. Several types of radicals can be generated from anodic oxidation or cathodic reduction of sulfonyl compounds and can initiate fluoroalkylation, benzenesulfonylation, cyclization or rearrangement. In this Review, we summarize the electrosynthesis developments involving sulfonyl compounds mainly in the last decade.

Copper-Catalyzed Radical N-Demethylation of Amides Using N-Fluorobenzenesulfonimide as an Oxidant.

An unprecedented N-demethylation of N-methyl amides has been developed by use of N-fluorobenzenesulfonimide as an oxidant with the aid of a copper catalyst. The conversion of amides to carbinolamines involves successive single-electron transfer, hydrogen-atom transfer, and hydrolysis, and is accompanied by formation of N-(phenylsulfonyl)benzenesulfonamide. Carbinolamines spontaneously decompose to N-demethylated amides and formaldehyde, because of their inherent instability.

Nitration and Cyclization of Arene-Alkynes: An Access to 9-Nitrophenathrenes.

A nitration and cyclization of arene-alkynes has been developed, affording 9-nitrophenathrenes efficiently. This reaction probably proceeds via addition of the nitrogen dioxide to the alkyne moiety, intramolecular radical addition of vinyl radical to one aryl ring, oxidation of radical intermediate into carbocation species, and elimination of a proton. In this transformation, Fe(NO3)3 was used as both nitro source and oxidant.

A reaction mode of carbene-catalysed aryl aldehyde activation and induced phenol OH functionalization.

The research in the field of asymmetric carbene organic catalysis has primarily focused on the activation of carbon atoms in non-aromatic scaffolds. Here we report a reaction mode of carbene catalysis that allows for aromatic aldehyde activation and remote oxygen atom functionalization. The addition of a carbene catalyst to the aldehyde moiety of 2-hydroxyl aryl aldehyde eventually enables dearomatization and remote OH activation. The catalytic process generates a type of carbene-derived intermediate with an oxygen atom as the reactive centre. Inexpensive achiral urea co-catalyst works cooperatively with the carbene catalyst, leading to consistent enhancement of the reaction enantioselectivity. Given the wide presence of aromatic moieties and heteroatoms in natural products and synthetic functional molecules, we expect our reaction mode to significantly expand the power of carbene catalysis in asymmetric chemical synthesis.

Cu(II)-Catalyzed 6π-Photocyclization of Dienynes.

The first 6π-photocyclization of dienynes was developed, which provides a new and effective protocol for the synthesis of the phenyl ring in excellent yields with nice functional group tolerance. In this transformation, the Cu(OTf)2 catalyst plays a key role in the conversion of alkyne moiety into an alkene-type moiety, which means that the dienyne reactant is converted into a triene-type substrate. Thus, this reaction proceeds via a Cu(II)-catalyzed 6π-photocyclization of triene-type derivatives.

Merging photoredox catalysis with Lewis acid catalysis: activation of carbon-carbon triple bonds.

Here, we demonstrate that merging photoredox catalysis with Lewis acid catalysis provides a fundamentally new activation mode of C-C triple bonds, to achieve the bond-forming reaction of alkynes with weak nucleophiles. Using a synergistic merger of Eosin Y and Cu(OTf)2, a highly efficient cyclization reaction of arene-ynes was developed.

[Multi-component of Cibotium baronetz decoction pieces via 1H-NMR spectroscopic analysis].

OBJECTIVE: 1H-NMR technology was carried out to investigate the chemical difference between 30 batches of Cibotium baronetz decoction pieces and look for new method for quality control of C. baronetz decoction pieces. METHOD: Six hundreds MHz H-NMR spectroscopy and principle component analysis (PCA) were used to discriminate between 30 batches of commercially available cibotium samples based on multi-component metabolite profiles. RESULT: Saccharide is the principle component of C. baronetz decoction pieces, and steroid and triterpene were the discriminately chemical component. Protocatechuic acid, protocatechuic aldehyde, cibotiumbaroside A, cibotiumbaroside B and 4-O-caffeoyl-D-glucoside could be used as the marker for controlling the quality of commercial C. baronetz decoction pieces. CONCLUSION: Pattern-recognition techniques applied to proton nuclear magnetic resonance (1H-NMR) spectra of 80% methanol extraction of C. baronetz could correctly discriminate not only the quality, but also the chemical component for batches of commercial C. baronetz decoction pieces.