Journal of Organic Chemistry最新文献

Herein, a highly efficient palladium-catalyzed tandem approach for the synthesis of 1,2,3-triazolo-azepine-fused benzosuberenes (TAABS) has been developed for the first time with vinyl bromide and internal alkynes as starting precursors. The given reaction proceeded under ligand- and additive-free conditions via sequential carbopalladation, followed by intramolecular electrophilic substitution. Also, the developed protocol has good functional group tolerance, wherein a range of sterically hindered TAABS analogues has been synthesized in appreciable yields. In addition, the developed methodology was also extended for the synthesis of 1,2.3-triazolobenzazepines from triazole-bearing aryl iodides and internal alkynes. The present protocol operates under relatively milder conditions with comparatively shorter reaction time. Furthermore, computational studies were also performed to validate the proposed mechanistic pathways. Additionally, the developed protocol is applicable to the gram-scale synthesis of TAABS analogues.

A benziodazole-type O₂NO-I(III) compound was used as a nitrating reagent to react with a series of electron-rich arenes including substituted phenols and anilines, affording the corresponding nitration products under mild conditions. Mechanistically, O₂NO-I(III) compound generates the reactive nitrogen dioxide (NO₂) species, which enables the nitration of phenols and anilines.

A novel and efficient electrochemical method for electroselective and controlled cross-coupling of isoindolinones with equivalent alcohols has been developed without the need for metal catalysts and strong bases under mild conditions. The reaction provides a novel strategy for the controllable and effective synthesis of 3-alkoxyl and N-hydroxymethyl-substituted isoindolinones, which is adjusted by 4-OH-TEMPO and tolerates various substrates. This protocol is an efficient tool for the construction of C-O and C-N bonds with high chemoselectivity.

We have studied copper-catalyzed cross-coupling of chiral α-CF₃-substituted allylboronic acids with α-diazoketones. The reaction proceeds with excellent regioselectivity and stereoselectivity via allylic rearrangement. The method is useful for formation a new allylic C(sp³)-C(sp³) bond with high selectivity. The poor yield is a limitation of this reaction.

An efficient method for copper-catalyzed asymmetric protoboration of allenyl sulfones with bis(pinacolato)diboron was developed, providing chiral allylic sulfones with high efficiency and excellent enantioselectivity. Notably, the directing effect of the sulfone group plays a pivotal role in achieving both high regioselectivity and enantioselectivity.

A comprehensive analytical protocol combining conductivity, diffusion-ordered NMR (DOSY), and photometric kinetic measurements is employed to analyze the nucleophilic reactivity of pyridinamide ion pairs in low-polarity organic solvents. The association patterns of these systems are found to strongly depend on cation size, with larger cations favoring the formation of cationic triple ion sandwich complexes together with free and highly nucleophilic anions. Kinetic studies using the ionic strength-controlled benzhydrylium method demonstrate that pyridinamide ions exhibit significantly higher nucleophilicities as compared to established organocatalysts, particularly in low-polarity solvents. Nucleophilicities are furthermore found to correlate well with Brønsted basicities measured in water and with Lewis basicities calculated in dichloromethane. Taken together, these findings provide quantitative guidelines for the future design of highly active Lewis base catalysts.

The total synthesis of the stereoisomer of muanlactam predicted by DP4+ calculations, which differed from that reported for the natural product on the relative configuration at C19, was completed, and the structure of the polyenic macrolactam was fully confirmed. Construction of the stereocenters involved the iterative enantio- and diastereoselective Krische's allylation reaction for the formal syn-1,3-diol and the addition of a propargylic Grignard reagent to Ellman's chiral nonracemic tert-butylsulfinamide for the enantiopure amine fragment. The conjugated triene and diene units were constructed by Suzuki-Miyaura cross-coupling reactions of the corresponding alkenylboronates and alkenyl iodides. Formation of the conjugated tetraene by Horner-Wadsworth-Emmons condensation of the functionalized partners was followed by challenging macrolactamization using hexafluorophosphate azabenzotriazole tetramethyluronium and N,N-diisopropylethylamine. The NMR data of the synthetic polyenic macrolactam matched those of the natural product, thus correcting the relative configuration of muanlactam at C19, which had previously been assigned by DP4.

In this work, we present a photoredox three-component reaction that enables the synthesis of medicinally relevant β-trifluoromethyl β-amino ketones from a N-trifluoroethylhydroxylamine derivative, styrenes and DMSO. Remarkably, fluoromethyl, difluoromethyl and pentafluoroethyl analogues are also accessed using the same reaction conditions. The mechanistic investigations, including radical trapping experiments, cyclic voltammetry, Stern-Volmer quenching studies and isotope labelling experiments support the photoinduced radical/polar crossover and Kornblum-type oxidation mechanisms. Finally, the applicability of the accessed organic skeletons is showcased by notable derivatization reactions.

Herein, we report two peri-regioisomers of B←N Lewis pair-functionalized perylenes: the centrosymmetric PBNPf1 and the mirror-symmetric PBNPf2. Mirror-symmetric functionalization more effectively tunes the photoelectronic properties. The LUMO energy levels of PBNPf1 and PBNPf2 are stabilized to -3.00 eV and -3.30 eV. Additionally, the emission maxima of PBNPf1 and PBNPf2 are shifted to 574 and 628 nm, with fluorescence quantum yields of up to 96% and 87%, respectively.

Chalcogen bond catalysis is gaining recognition in organocatalysis due to its environmental benignity and relatively low cost. The hypervalent selenium salts can drive the hydroarylation of styrene and phenol, and hypervalent chalcogen···π catalysis has been proposed [Zhang, Q. Angew. Chem., Int. Ed. 2022, 61, e202208009]. In this work, the hydroarylation of styrene and phenol catalyzed by cyclic hypervalent selenium-based catalysts is investigated by density functional theory (DFT) calculations, and two activation modes are observed: one is on the styrene (π-activation mode), and the other is on the phenol (O-activation mode). The energy barriers via the O-activation mode are lower than those of the π-activation mode, and our proposed O-activation mode in this work may be more favorable. For the O-activation mode, energy barriers for the ortho-hydroarylation are lower than those for the para-hydroarylation, which is consistent with the experimental observation that the ortho-hydroarylation product is the major product and supports our proposed O-activation mode. Further investigation revealed that the stronger electrostatic interaction is the main factor leading to the ortho-hydroarylation in the O-activation mode compared to the para-hydroarylation. Moreover, the substituent effect of cyclic hypervalent selenium-based catalysts on the reactivity was investigated. This work would provide a valuable perspective on expanding applications for chalcogen bond catalysis.