Delivering 2-Aryl Benzoxazoles through Metal-Free and Redox-Neutral De-CF3 Process

Photocatalytic Hydro Tri/Difluoromethylation of Alkenes with Bench Stable Tri/Difluoromethylating Reagents

Herein, we demonstrate the synthesis and characterization of bench stable tri/difluoromethylating reagents and their potential applications in redox neutral hydro tri/difluoromethylation of alkenes enabled by visible light. The new tri/difluoromethylating reagents are obtained on a gram-scale through simply cyclocondensation of commercially available anthranilamide with phenyltrifluoro or difluoromethyl ketone. Preliminary mechanistic studies indicated that a canonical photoredox catalytic cycle is being operative. DFT studies support this and further reveal that deprotonation occurs before radical cleavage. DFT studies also show that the better yield with HCF2 reagent is attributed to the favorable expulsion of the corresponding radical moiety.

Synthesis of Aryl-methylene Ethers through Pd(0)-Catalyzed Coupling between Hydrobenzoxazoles and Dichloromethane

Using dichloromethane (DCM) as the C1 feedstock, the first Pd(0)-catalyzed synthesis of aryl-methylene ether motifs from hydrobenzoxazoles (hydrothiazoles) has been reported. This protocol has exhibited an ample substrate scope (38 examples) and wide functional group tolerance. Aryl-methylene ether adducts have been successfully engaged in coupling with isocyanate to provide bis-iminoisoindolinones. In this reaction, DCM has served as a twofold electrophile for reaction with hydrobenzoxazoles via double C-Cl bond cleavage.

Synthesis of Naphtho[2,3-d]oxazoles via Ag(I) Acid-Mediated Oxazole-Benzannulation of ortho-Alkynylamidoarylketones

A cascade oxazole-benzannulation for the synthesis of naphtho[2,3-d]oxazoles has been developed employing ortho-alkynylamidoarylketones as substrates. This procedure provides the advantage of preparing a wide variety of substituents on naphtho[2,3-d]oxazole structures. In addition, o-alkynylamidoarylketones could be prepared from easily accessible and a wide variety of commercially available starting materials. Therefore, this method is a judicious choice of strategy to synthesize naphtho[2,3-d]oxazoles with a great variety of substituents. In this work, 27 examples were demonstrated to provide the desired products in moderate to good yields.

Reductive Cleavage of C(sp2)-CF3 Bonds in Trifluoromethylpyridines

A reductive detrifluoromethylation protocol has been developed making use of an earth-abundant alkoxide base and silicon hydride species. A variety of pyridine and quinoline substrates bearing alkyl, aryl, and amino functional groups are reduced in moderate to high yields. The reaction is chemoselective for C(sp²)-CF₃ groups located at the 2-position on the pyridine ring, leaving trifluoromethyl groups located elsewhere on the molecule intact. Preliminary mechanistic studies demonstrate that the combination of silane and base generates a strongly reducing system that may transfer an electron to electron-deficient π systems.

Synthesis and Spectral Properties of Aggregation-Induced Emission-Active Push-Pull Chromophores Based On Isoindole Scaffolds

A new class of tailor-made push-pull isoindole fluorophores has been synthesized through the combination of Suzuki coupling and Knoevenagel reactions. The efficient synthetic strategy rendered the isoindole scaffold as the π-bridge and the isolation spacer and provided dyes bearing various types of electron donors and electron acceptors for manipulating their energy gaps and tuning their absorptions and emissions. Most of the N-alkylated isoindole dyes showed aggregation-induced emission behaviors suitable for bioimaging and nice solid-state emission with maxima up to 851 nm.