Search

The mechanism of copper-mediated coupling reactions has aroused widespread interest, and it has been found to not be as simple as initially thought. In this article, we give an overview of the recent advances in this field. Notably, we focus on whether the presence of CuIII is adopted in the catalytic cycle. Attention is paid to the key CuII species, which can be generated by radical-type or single electron transfer (SET) oxidation of CuI. The CuII species can be oxidized to CuIII by SET or using a nucleophilic radical for further reductive elimination. Alternatively, radical-type substitution or bimetallic reductive elimination can avoid formation of CuIII, and coupling reactions can also be achieved. [ABSTRACT FROM AUTHOR]

Herein, we report a Pd-catalyzed regiospecific cycloaromatization of β-bromoenal and vinyl borate esters to synthesize m-alkenyl substituted benzaldehydes. This allows the construction of complex molecules from simple materials, which may be useful in the search for new optical materials. [ABSTRACT FROM AUTHOR]

Enynones are powerful synthons for constructing furan derivatives in the presence of transition metal catalysts. Unlike the conventional intramolecular nucleophilic attack with the activation of coinage metals, we propose that enynones undergo an oxidative cyclization process with a Pd(0) species. The full catalytic cycle involves oxidative cyclization, isocyanide insertion, and reductive elimination, which was supported by DFT calculations. Geometric and electronic analyses confirmed the oxidative cyclization process, which proceeds VIA a Pd(II) intermediate. [ABSTRACT FROM AUTHOR]

In the presence of multiple electrophiles, the reaction sequence is a critical mechanistic problem. Here, we report a theoretical study on the mechanism of phosphine-catalyzed [8+2] cycloaddition of heptafulvenes and allenoate. DFT calculations showed that electrophilicity is the barrier for nucleophilic attack, while it fails in the prediction of priority. [ABSTRACT FROM AUTHOR]

A systemical computational study was performed to explore the mechanism and origin of selectivities on the organocatalytic arylation of azonaphthalenes with α-chloroaldehydes. The calculated results reveal that the nucleophilicity of active sites and the hydrogen bonds respectively regulate chemo- and stereoselectivities and, for the first time, N-heterocyclic carbene (NHC) can act as a multiple functional base (MFB) catalyst in one system. [ABSTRACT FROM AUTHOR]

A mixture of pathways including the use of catalyst was proposed for a dirhodium-mediated triazole activation–cycloaddition. This proposal was supported by the results of density functional theory (DFT) calculations, and was indicated to involve a non-catalyzed cleavage of the triazole N–N bond followed by a dirhodium-assisted denitrogenation. Electron-deficient carboxylates were found to be favourable for the rate-determining denitrogenation step. [ABSTRACT FROM AUTHOR]

Here, we report the development of novel PET radiotracer ([11C]CW22) of BET proteins. In vivo imaging results in rodents and nonhuman primates (NHP) demonstrate that [11C]CW22 has excellent brain uptake, good specificity, good selectivity, suitable metabolism, appropriate kinetics and distribution in the brain. Our studies demonstrated that [11C]CW22 exhibits ideal properties as a PET imaging probe of BET proteins for further validation. [ABSTRACT FROM AUTHOR]

Theoretical calculations have been performed to investigate the mechanism and stereoselectivity of rhodium-catalysed intramolecular [3+2] cycloaddition for construction of a substituted hexahydropentalene complex. A new C–C bond cleavage mechanism, retro-Aldol-type, is proposed and verified for this Rh-catalysed [3+2] cycloaddition reaction. [ABSTRACT FROM AUTHOR]

Herein, we report an efficient and practical strategy for the synthesis of five types of imidazo[2,1-a]isoquinolines via Cp*RhIII-catalyzed [4+2] annulation of 2-arylimidazoles and α-diazoketoesters, whose structural and substituted diversity at 5- or 6-position can be precisely controlled by the α-diazoketoester coupling partners. Compared with previous reports, in this study, we merged two attractive C–C cleavage strategies (retro-Claisen and decarboxylation) into the classical C–H functionalization/condensation process by choosing appropriate ester groups (–COOEt, –COOtBu or –COOiPr) or inexpensive additives (HOAc or KOAc). Moreover, the synthetic efficacies of these methods were demonstrated by the concise synthesis of several bioactive compounds and the late-stage modification of representative drugs. [ABSTRACT FROM AUTHOR]

In this work, we develop an oxidation-induced C–H functionalization strategy, which not only leads to a new avenue to build C–N bonds, but also leads to different site-selectivity compared with “classic directing-groups”. The high selectivity of our new catalytic system originates from the heterogeneous electron-density distribution of the radical cation species which are induced by single electron transfer between the aromatics and oxidant-Cu(ii) species. [ABSTRACT FROM AUTHOR]

In this study, we broke through the directing function of the amide group. The coordination interaction between metal and directing-group enhanced the reactivity of the substrate. Using this strategy, we realized the selective amination of 8-aminoquinolines at the C5 position via employing azoles as the source of amine. Various kinds of 8-aminoquinolines and different substituted azoles were compatible to afford the corresponding C–N coupling products. [ABSTRACT FROM AUTHOR]

Enantioselective alkynylation of cyclic N-sulfonyl α-ketiminoesters with terminal alkynes was developed by using an Ni(ClO4)2/(R)-DTBM-Segphos complex as a catalyst. A range of propargylic amides bearing quaternary stereocenters were afforded in excellent enantioselectivities (up to 97% ee). Theoretical studies revealed that this reaction proceeded via a Friedel–Crafts-type reaction pathway. [ABSTRACT FROM AUTHOR]

Pd-catalyzed selective amine-oriented C8–H bond functionalization/N-dealkylative carbonylation of naphthyl amines has been achieved. The amine group from dealkylation is proposed to be the directing group for promoting this process. It represents a straightforward and easy method to access various biologically important benzo[cd]indol-2(1H)-one derivatives. [ABSTRACT FROM AUTHOR]

The investigation into the active copper(i) catalysts from copper(ii) precursors has become a fundamental and important task in copper catalysis. In this work, we demonstrate that the tBuO− anion serves not only as a base but also as a mediator to promote the reduction of Cu(ii) to Cu(i) in copper catalysis. XAFS and EPR spectroscopy evidence the [Cu(OtBu)3]− ate complex as the key intermediate which undergoes homolytic-cleavage of the O–Cu(ii) bond generating [Cu(OtBu)2]− ate complex. [ABSTRACT FROM AUTHOR]

Molecular iodine was found to be an effective redox catalyst for the oxidative cross-coupling of carbonyl compounds with terminal alkynes. In this work, we demonstrated that iodine could tune radical reactivity through reversible C–I bond formation for controlling the reaction selectivity. This iodine catalysis protocol provided an easy way for the synthesis of various furans and indolizines. [ABSTRACT FROM AUTHOR]