Organic & Biomolecular Chemistry最新文献

Incorporating a steric barrier between the two stations in a bistable [2]rotaxane based on monopyrrolotetrathiafulvalene and cyclobis(paraquat-p-phenylene) allows the high-energy metastable-state co-conformation to be physically isolated following a single redox cycle, thus making it possible to store energy (4.4 J L^-1) and to follow its interconversion back to the ground-state co-conformation.

A simple and efficient Ru(II)-catalyzed olefination of 3-(arylbenzylidene)indolin-2-ones with alkenes is described. This is an atom and step-economical strategy with a wide substrate scope, good functional group tolerance, and suitability for gram scale synthesis. A plausible mechanism is also proposed for this synthetic transformation involving the formation of a 5-membered ruthenacycle and insertion of the alkene followed by β-hydride elimination to deliver the desired product.

A diverse array of fused [6-6-5] tricyclic heterocycles has been synthesized via the dimerization and dearomative cyclization of benzene derivatives under visible light irradiation. The initiation of the cascade process is likely from aryloxy radicals, engendered through proton-coupled electron transfer by the photoexcited vinylidene ortho-quinone methide (VQM) and a Brønsted base.

NMR spectral and theoretical analyses of homologous prolyl carbamates reveal subtle charge transfer tetrel bonding interactions (TBIs), selectively stabilizing their cisPro rotamers. These TBIs involve C-terminal-amide to N-terminal carbamate carbonyl-carbonyl (n → π* type) followed by intra-carbamate (n → σ* type) charge transfer interactions exclusively in the cisPro motif. The number of TBIs and hence the cisPro stability increase with increasing number of C^β groups at the carbamate alcohol. Increasing solvent polarities also increase the relative cisPro carbamate stabilities.

We described herein a three-component radical alkyl-acylation of [1.1.1]propellane via a visible-light photoredox single electron transfer process, demonstrating an efficient approach for accessing a diverse array of 1,3-disubstituted BCP ketone derivatives. The synthetic utility of the present radical protocol was further demonstrated by the Baeyer-Villiger oxidation of the BCP ketone for BCP ester formation.

The chemistry of tetraarylammonium salts, first explored in the 1960s Soviet Union, has long been a dormant field of research. This is owing to the inherent difficulty in adding a fourth benzene ring to the nitrogen atom of the sterically demanding and low-nucleophilicity triphenylamine molecule. Only recently have new developments in synthetic methodology made access to tetraarylammonium salts less of a tour de force, and first applications are beginning to emerge. As a consequence, the number of publications in this field of research is growing. The review covers the complete field of research, from the beginnings to the present day.

Chiral sulfones are key structural motifs that extensively exist in natural products, drugs, and biologically active compounds. During the past few decades, rapid development has been made with respect to the highly enantioselective synthesis of chiral sulfones, in which the catalytic asymmetric hydrogenation of unsaturated sulfones provides an efficient and powerful methodology to construct chiral sulfones and their derivatives. This review highlights the progress achieved in transition metal (ruthenium, rhodium, iridium, and nickel) catalyzed direct asymmetric hydrogenation of a variety of unsaturated sulfones from the aspects of the substrate scope, catalytic mechanisms, and applications in the synthesis of biologically active molecules.

In this study, a carbazole-based mitochondria-targeted colorimetric and NIR ratiometric fluorescent probe 1 for biothiols based on the thiol-chromene click reaction was subtly designed and synthesized. Upon interaction with biothiols (Cys, Hcy and GSH), the absorption of 1 shifted from 496 nm to 388 nm, while its fluorescence spectrum shifted from 650 nm to 530 nm. These transformations were accompanied by a visible color change from pink to colorless under visible light and from red to green when observed under a 365 nm UV lamp, which can be attributed to the click reaction of biothiols with the α,β-unsaturated ketone of the chromene moiety, subsequent pyran ring-opening and phenol formation as well as 1,6-elimination of a p-hydroxybenzyl moiety yielding 2. These advancements in 1 have allowed us to ratiometrically detect biothiols with high sensitivity (LODs of 97 nM, 94 nM and 93 nM for Cys, GSH and Hcy, respectively), a large Stokes shift (154 nm) and excellent selectivity. In addition, 1 can target mitochondria and image the fluctuation of intracellular biothiols through fluorescence ratiometry. Furthermore, the novel design strategy of modifying chromene to the N atom of quinoline was proposed for the first time.

A palladium-catalyzed cascade reaction of α,β-unsaturated N-tosylhydrazones with iodoarene derivatives containing a nucleophilic group has been developed, which provides facile access to 2H-chromenes and 2H-quinolines, respectively. Additionally, the double Pd-carbene migratory insertion/nucleophilic substitution processes for the synthesis of a ternary heterocyclic skeleton were possible in the developed catalytic system.

The thermal and acid-catalyzed rearrangement mechanisms of N-methyl-N-nitroanilines were theoretically investigated via density functional theory (DFT) calculations for all possible proposed mechanisms. The results indicate that the thermal rearrangement of N-methyl-N-nitroanilines undergoes a radical pair complex mechanism through the homolysis of their N-N bond to generate a radical pair complex and the recombination of the radical pairs followed by aromatization. For the acid-catalyzed rearrangements, N-methyl-N-nitroanilines are first protonated on the nitrogen atom of their aniline moiety and then generate protonated N-methyl-O-nitroso-N-phenylhydroxylamines through a three-membered spirocyclic oxadiaziridine transition state. The N-protonated N-methyl-O-nitroso-N-phenylhydroxylamines favor homolytic dissociation to generate N-methylaniline cationic radical and nitrogen dioxide complexes, which further combine together and aromatize to afford protonated N-methyl-o-nitroanilines and N-methyl-p-nitroanilines, respectively. The radical pair complexes are more stable than the corresponding solvent-caged radical pairs. The thermal rearrangements require higher activation energy than the corresponding acid-catalyzed rearrangements.