Chengjian Zhu

Visible‐Light‐Induced Trifluoromethylation of N‐Aryl Acrylamides: A Convenient and Effective Method To Synthesize CF3‐Containing Oxindoles Bearing a Quaternary Carbon Center

Trifluoromethylation/arylation: N-aryl acrylamides undergo visible-light-induced tandem trifluoromethylation/arylation in the presence of a ruthenium photocatalyst with Tognis reagent as the CF3 source. This reaction serves as a powerful and ecofriendly synthetic method for the preparation of a variety of CF3 -containing oxindoles bearing a quaternary carbon center.

Na+ triggered fluorescence sensors for Mg2+ detection based on a coumarin salen moiety.

Two coumarin salen-based sensors CS1 and CS2 can exhibit a pronounced fluorescence enhancement response toward Mg(2+) as high as 36-fold (CS1) and 111-fold (CS2) in the presence of Na(+) as a synergic trigger. More importantly, the fluorescent color of CS1 was bright green instead of weak yellow after the addition of Mg(2+) and Na(+) together, which can be easily detected by the naked eye.

A highly selective and sensitive polymer-based OFF-ON fluorescent sensor for Hg2+ detection incorporating salen and perylenyl moieties

A chiral conjugated polymer sensor with incorporated (R,R)-salen and perylenyl moieties in the main chain backbone could be obtained by the polymerization of 1,7-bis((3-formyl-4-hydroxyphenyl)ethynyl)perylene-3,4:9,10-tetracarboxylic tetrabutylate (M-1) with (R,R)-1,2-diaminocyclohexane (M-2) via a nucleophilic addition–elimination reaction. The polymer sensor can emit the fluorescence situated at 635 nm due to the introduction of a strong fluorophore perylenyl group. Compared with the other cations (including Na+, K+, Ca2+, Ag+, Ni2+, Cd2+, Pb2+, Cr3+ Al3+, Fe3+, Co2+, Zn2+), only Hg2+ can lead to the most pronounced response of the polymer sensor, which is as high as a 26-fold fluorescence enhancement without interference from other metal ions. More importantly, the fluorescent color of the polymer sensor displays an obvious change from red to bright yellow upon addition of Hg2+, which could be easily detected by the naked eye. The results indicate that the polymer sensor with incorporated (R,R)-salen and perylenyl moieties can be favorably utilized for the development of a potential sensor for Hg2+ detection.

A Highly Selective Fluorescence‐Based Polymer Sensor Incorporating an (R,R)‐Salen Moiety for Zn2+ Detection

A chiral polymer incorporating an (R,R)-salen moiety was synthesized by the polymerization of (R,R)-1,2-diaminocyclohexane with 2,5-dibutoxy-1,4-di(salicyclaldehyde)-1,4-diethynyl-benzene by a nucleophilic addition-elimination reaction. The fluorescence responses of the (R,R)-salen-based polymer toward various metal ions were investigated by fluorescence spectra. Compared with other cations, such as Na(+), K(+), Mg(2+), Ca(2+), Mn(2+), Fe(2+), Fe(3+), Co(2+), Ni(2+), Cu(2+), Ag(+), Cd(2+), Hg(2+), and Pb(2+), Zn(2+) can lead to a pronounced fluorescence enhancement as high as 7.8-fold together with an obvious blue-shift change of the chiral polymer. More importantly, the fluorescent color of the polymer changed to bright blue instead of weak yellow after addition of Zn(2+), which can be easily detected by the naked eye. The results indicate that this kind of chiral polymer, incorporating an (R,R)-salen moiety as a receptor in the main chain backbone, can exhibit high sensitivity and selectivity for Zn(2+) recognition.

Visible‐Light Photoredox‐Catalyzed C−H Difluoroalkylation of Hydrazones through an Aminyl Radical/Polar Mechanism

An unprecedented visible-light-induced direct C-H bond difluoroalkylation of aldehyde-derived hydrazones was developed. This reaction represents a new way to synthesize substituted hydrazones. The salient features of this reaction include difluorinated hydrazone synthesis rather than classical amine synthesis, extremely mild reaction conditions, high efficiency, wide substrate scope, ease in further transformations of the products, and one-pot syntheses. Mechanistic analyses and theoretical calculations indicate that this reaction is enabled by a novel aminyl radical/polar crossover mechanism, with the aminyl radical being oxidized into the corresponding aminyl cation through a single electron transfer (SET) process.

Gold-complexes catalyzed oxidative α-cyanation of tertiary amines

Oxidative α-cyanation of tertiary amines is catalyzed by gold complexes with trimethylsilyl cyanide to afford the corresponding α-aminonitriles in the presence of tert-butyl hydroperoxide in good to excellent yields under acid-free conditions at room temperature.

Ruthenium‐Catalyzed C7 Amidation of Indoline CH Bonds with Sulfonyl Azides

A ruthenium-catalyzed direct C7 amidation of indoline C-H bonds with sulfonyl azides was developed. This procedure allows the synthesis of a variety of 7-amino-substituted indolines, which are useful in pharmaceutical. The good functional tolerances, as well as the mild conditions, are prominent feature of this method.

Visible-Light-Promoted Radical C–H Trifluoromethylation of Free Anilines

The trifluoromethyl-substituted anilines are biologically active compounds and useful building blocks. In this communication, we have developed the first visible-light-induced radical trifluoromethylation of free anilines with the commercially available and easily handled Togni reagent at room temperature. The resulting products were successfully transformed into a variety of valuable fluorine-containing molecules and heterocyclic compounds. This protocol provides an economical and powerful route to trifluoromethylated free anilines.

A visible-light-promoted aerobic C–H/C–N cleavage cascade to isoxazolidine skeletons

The bicyclic isoxazolidine scaffolds are the ubiquitously recurring motifs in alkaloids. Despite of their facile biosynthesises in nature, the laboratory synthesis of these derivatives is still complicated. In this paper, the isoxazolidine derivatives are concisely constructed in one process with excellent stereoselectivity from simple tertiary amines through a C–H activation-retro-aza-Michael-oxidation-cyclization tandem sequence by means of visible-light. This protocol provides a concise approach to dactylicapnosinine derivatives.

Organocatalytic oxa/aza-Michael–Michael Cascade Strategy for the Construction of Spiro [Chroman/Tetrahydroquinoline-3,3′-oxindole] Scaffolds

A new useful and effective chiral amine-catalyzed oxa- and aza-Michael-Michael cascade methodology for the construction of enantiomerically enriched indolinones spiro-fused with chromans or tetrahydroquinolines is reported. By employing suitable organocatalysts depending on the different Michael donors (Ar-OH/Ar-NHR), the processes offered excellent stereocontrol (dr >20:1, >99% ee) under mild conditions.