Hypervalent Iodine Promoted Selective [2 + 2 + 1] Cycloaddition of Aromatic Ketones and Methylamines: A One-Pot Access to 1-Pyrrolines.

Herein, a versatile highly regioselective three-component annulation of simple aromatic ketones and methylamines using a hypervalent iodine reagent for polyarylated 1-pyrrolines has been described in good to excellent yields. Meanwhile, unsymmetrical 1-pyrroline isomers could be realized and synthesized. Such an intriguing one-pot two-step tandem assembly strategy with green conditions and high regioselectivity shows predictable inspiration in related annulation reactions.

Photo-induced tungsten-catalyzed cascade synthesis of pyrrolo[2,1-]isoquinoline-1,3-dicarboxylate and its reaction mechanism.

A pyrrolo[2,1-]isoquinoline core structure is prevalent in marine and other natural products. This article describes a tungsten-catalyzed [3+2] cycloaddition aromatization of dihydroisoquinoline ester and maleic anhydride or an acrylate. The photochemical reaction tolerates a range of functional groups such as ester, cyano, ketone, bromide, and alkene.

Visible Light Mediated Chemoselective Hydroxylation of Benzylic Methylenes.

We have developed a metal-free photocatalytic selective hydroxylation of benzylic methylenes to secondary alcohols. This approach utilizes low-cost eosin Y as photocatalyst, O as green oxidant, and inexpensive triethylamine as inhibitor for overoxidation. The mild reaction conditions enable the production of secondary alcohols with 56-95% yields, making it a promising and environmental-friendly method for the synthesis of secondary alcohols from benzylic methylenes.

Difluoromethylated Difunctionalization of Alkenes under Visible Light.

Difluoromethylated compounds usually act as bioisosteres for alcohol functional groups and show unique physicochemical and biological properties. The cyano-difluoromethylation of alkenes using 5-((difluoromethyl)sulfonyl)-1-phenyl-1-tetrazole as a CFH radical difluoromethyl precursor was developed to afford nitriles including a CFH group. A low-cost, stable, easily handled 5-((difluoromethyl)sulfonyl)-1-methyl--tetrazole (DFSMT) was synthesized and applied as the radical CFH reagent.

Synthesis of functionalized tetrahydrodibenzo[,][1,8]naphthyridin-1(2)-ones through base-promoted annulation of quinoline-derived dipolarophiles and cyclic enaminones.

An eco-friendly and metal-free method for the synthesis of tetrahydrodibenzo[,][1,8]naphthyridin-1(2)-ones was established. Quinoline-derived dipolarophiles and cyclic enaminones as starting materials undergo a 1,4-Michael addition/SAr tandem annulation reaction affording the target products. This approach features transition metal-free conditions, good functional group tolerance and operational simplicity.

Direct photo-induced reductive Heck cyclization of indoles for the efficient preparation of polycyclic indolinyl compounds.

The photo-induced cleavage of C(sp)-Cl bonds is an appealing synthetic tool in organic synthesis, but usually requires the use of high UV light, photocatalysts and/or photosensitizers. Herein is described a direct photo-induced chloroarene activation with UVA/blue LEDs that can be used in the reductive Heck cyclization of indoles and without the use of a photocatalyst or photosensitizer. The indole compounds examined display room-temperature phosphorescence.

Luminescent tungsten(vi) complexes as photocatalysts for light-driven C-C and C-B bond formation reactions.

The realization of photocatalysis for practical synthetic application hinges on the development of inexpensive photocatalysts which can be prepared on a large scale. Herein an air-stable, visible-light-absorbing photoluminescent tungsten(vi) complex which can be conveniently prepared at the gram-scale is described. This complex could catalyse photochemical organic transformation reactions including borylation of aryl halides, such as aryl chloride, reductive coupling of benzyl bromides for C-C bond formation, reductive coupling of phenacyl bromides, and decarboxylative coupling of redox-active esters of alkyl carboxylic acid with high product yields and broad functional group tolerance.

Ruthenium porphyrin catalysed intermolecular amino-oxyarylation of alkenes to give primary amines via a ruthenium nitrido intermediate.

Ruthenium porphyrin catalysed direct intermolecular amino-oxyarylation of alkenes including styrenes and 1,3-dienes to give primary amines with O-(2,4-dinitrophenyl)hydroxylamine as the amine source was achieved in moderate to good yields under mild reaction conditions. Spectroscopic analyses revealed that a ruthenium nitrido complex was the key reaction intermediate for the amino-oxyarylation reaction.

Strongly Luminescent Tungsten Emitters with Emission Quantum Yields of up to 84 %: TADF and High-Efficiency Molecular Tungsten OLEDs.

Metal-TADF (thermally activated delayed fluorescence) emitters hold promise in the development of next generation light-emitting materials for display and lighting applications, examples of which are, however, largely confined to Cu and recently Au , Ag , and Au emitters. Herein is described the design strategy for an unprecedented type of metal-TADF emitter based on inexpensive tungsten metal chelated with Schiff base ligand that exhibit high emission quantum yields of up to 56 % in solutions and 84 % in thin-film (5 wt % in 1,3-bis(N-carbazolyl)benzene, mCP) at room temperature. Femtosecond time-resolved emission (fs-TRE) spectroscopy and DFT calculations were undertaken to decipher the TADF properties.

Nickel-catalyzed α-arylation of zinc enolates with polyfluoroarenes via C-F bond activation under neutral conditions.

The first nickel-catalyzed α-arylation of 2-(polyfluorophenyl) pyridine with zinc enolates of esters or amides via C-F bond activation under neutral conditions is described. A variety of functional groups such as ester, amide, ether, and amine were tolerated. This method provides a simple and useful tool to synthesize fluorinated α-aryl carboxylic acids and α-aryl amides that are important intermediates for drug discovery.

Palladium-catalyzed coupling of polyfluorinated arenes with heteroarenes via C-F/C-H activation.

The first palladium-catalyzed coupling of 2-pyridyl-polyfluoroarenes and benzoxazole, thiazole, benzothiazole, benzoimidazole, oxazole or oxadiazole via a concurrent C-F/C-H activation is described. Initial mechanistic studies showed that C-F activation of perfluoroarene is likely the rate-limiting step of the catalytic cycle. This protocol provides a useful and operationally simple process to functionalized polyfluoroarenes.

Selective palladium-catalyzed C-F activation/carbon-carbon bond formation of polyfluoroaryl oxazolines.

A selective palladium-catalyzed Suzuki-Miyaura coupling reaction of polyfluorophenyl oxazolines through ortho C-F activation is described. It was found that reactions with DPPF as the ligand occurred much faster than those with other ligands. A variety of arylboronic acids including challenging functionalized arylboronic acids such as enolizable ketones, aldehyde, cyano, ester, and trifluoromethyl groups were tolerated with the reaction conditions.