Constructing an Asymmetric Covalent Triazine Framework to Boost the Efficiency and Selectivity of Visible-Light-Driven CO2 Photoreduction.

The photocatalytic reduction of CO2 represents an environmentally friendly and sustainable approach for generating valuable chemicals. In this study, a thiophene-modified highly conjugated asymmetric covalent triazine framework (As-CTF-S) is developed for this purpose. Significantly, single-component intramolecular energy transfer can enhance the photogenerated charge separation, leading to the efficient conversion of CO2 to CO during photocatalysis. As a result, without the need for additional photosensitizers or organic sacrificial agents, As-CTF-S demonstrates the highest photocatalytic ability of 353.2 µmol g-1 and achieves a selectivity of ≈99.95% within a 4 h period under visible light irradiation. This study provides molecular insights into the rational control of charge transfer pathways for high-efficiency CO2 photoreduction using single-component organic semiconductor catalysts.

Palladium-Catalyzed Chemoselective Synthesis of 2-Aminocinnamyl Esters via Sequential Amination and Olefination of Aryl Iodides.

We report a highly chemoselective palladium-catalyzed Catellani-type amination of aryl iodides terminated by the Heck reaction using allylic esters as terminating reagents. 2-Aminocinnamyl esters were formed exclusively via ß-H elimination rather than ß-OAc elimination without the assistance of a silver salt. This protocol represents a useful extension of Catellani-type transformations.

Modular and Stereoselective Synthesis of C-Aryl Glycosides via Catellani Reaction.

In this work, we describe a Catellani-type C-H glycosylation to provide rapid access to various highly decorated α-C-(hetero)aryl glycosides in a modular and stereoselective manner (>90 examples). The termination step is flexible, which is demonstrated by ipso-Heck reaction, hydrogenation, Suzuki coupling, and Sonogashira coupling. Application of this methodology has been showcased by preparing glycoside-pharmacophore conjugates and a dapagliflozin analogue. Notably, the technology developed herein represents an unprecedented example of Catellani-type alkylation involving an SN1 pathway.

Rhodium(II)-catalyzed multicomponent assembly of α,α,α-trisubstituted esters via formal insertion of O-C(sp3)-C(sp2) into C-C bonds.

The direct cleavage of C(CO)-C single bonds, delivering otherwise inaccessible compounds, is a significant challenge. Although the transition metal-catalyzed insertion of functional groups into C(CO)-C bonds has been studied, strained ketone substrates or chelating assistance were commonly required. In this article, we describe a rhodium(II)-catalyzed three-component reaction of 1,3-diones, diazoesters, and N,N-dimethylformamide (DMF), leading to an unusual formal insertion of O-C(sp3)-C(sp2) into unstrained C(CO)-C bonds. This procedure provides a rapid entry to a gamut of otherwise inaccessible α,α,α-trisubstituted esters/amide from relatively simple substrates in a straightforward manner. 55 examples of highly decorated products demonstrate the broad functional group tolerance and substrate scope. The combination of control experiments and isotope-labeling reactions support that O, C(sp3), and C(sp2) units derive from 1,3-diones, diazoesters, and DMF, respectively.

Synthesis of 3-(2-quinolyl) chromones from ynones and quinoline N-oxides via tandem reactions under transition metal- and additive-free conditions.

A novel method for the synthesis of 3-(2-quinolyl) chromones through a tandem [3+2] cycloaddition/ring-opening/O-arylation from ynones and quinoline N-oxides has been developed. This protocol proceeds under transition metal- and additive-free conditions and can be amplified to the gram level in 91% yield. 3-(1-Isoquinolyl) and 3-(2-pyridyl) chromones are also successfully synthesized using isoquinoline and pyridine N-oxides under basic conditions. Various heteroarene-contaning chromones were afforded in 30-98% yields, which are difficult to be obtained and are compounds of interest in pharmaceutical chemistry and chemical biology.

Ruthenium(II)-Catalyzed Construction of Isocoumarins via Dual C-H/C-C Activation of Sulfoxonium Ylides.

A ruthenium(II)-catalyzed annulation between two molecules of sulfoxonium ylides is achieved, generating a variety of substituted isocoumarins in reasonable yields. This strategy features dual C-H/C-C activation in one pot and has a wide substrate scope and good functional group tolerance.

Ruthenium(ii)-catalyzed chemoselective deacylative annulation of 1,3-diones with sulfoxonium ylides via C-C bond activation.

The first successful example of deacylative annulation of 1,3-diones with sulfoxonium ylides was achieved through Ru(ii)-catalyzed C-C bond activation. The excellent chemoselectivity and broad substrate scope render this method a practical and versatile approach for the preparation of (hetero)aryl and alkenyl substituted furans, which are valuable units in many biologically active compounds and functional materials. A preliminary mechanistic study reveals that this process involves a deacylative α-ruthenation to generate key alkyl Ru(ii) intermediates with the release of a benzoic acid fragment.

Copper-Catalyzed Three-Component Cascade Michael Addition/Heck-Type Alkylation/Annulation: Accessing Fully Substituted 1,3-Dihydro-2H-pyrrol-2-ones.

We report a highly efficient copper-catalyzed three-component reaction of alkylamines, acetylenedicarboxylates, and α-bromocarbonyls for the assembly of fully substituted 1,3-dihydro-2H-pyrrol-2-ones. A variety of alkylamines and ammonium salt are functionalized with acetylenedicarboxylates and α-bromocarbonyls. N-aryl enaminoesters are also successfully alkylated with α-bromocarbonyls. This protocol is understood to proceed through radical Heck-type coupling of in-situ-generated bulky trisubstituted alkenes with bulky tertiary alkyl bromides, which is realized for the first time.

Rhodium(III)-Catalyzed Regioselective C3-H Acylmethylation of [2,2'-Bipyridine]-6-carboxamides with Sulfoxonium Ylides.

A rhodium(III)-catalyzed C-H acylmethylation of tridentate [2,2'-bipyridine]-6-carboxamides was developed. A variety of [2,2'-bipyridine]-6-carboxamides could be monoalkylated exclusively at the C3 position with sulfoxonium ylides as carbene precursors, giving 3-alkylated products in high yields. This protocol proceeds through a rollover cyclometalation pathway, has a broad range scope of substrates, and exhibits excellent functional group tolerance.