Organic chemistry frontiers : an international journal of organic chemistry最新文献

An efficient and straightforward approach to planar indolizine-fused azepines via Brønsted acid catalyzed [5 + 2] cycloaddition of ortho-indolizinyl anilines with cyclopentenediones has been established. This reaction involves a Friedel–Crafts addition/oxidation/Schiff-base condensation tandem process and features mild conditions, broad substrate scope and diverse further transformations. Furthermore, the intriguing planar azepines exhibited favorable photoluminescence properties, which indicated their potential as fluorescent materials.

A visible-light-induced decarboxylative selenocyanation reaction of aliphatic carboxylic acids for the formation of C(sp³)–SeCN bonds has been developed. The electrophilic N-selenocyanatophthalimide and a pyrylium salt were applied as a SeCN radical precursor and an organic photocatalyst, respectively. The transformation could proceed smoothly without transition metals, oxidants and additional bases, affording the corresponding alkyl selenocyanates in moderate to good yields. This method is characterized by its simplicity, wide substrate scope and mild conditions.

A photocatalytic three-component reaction of alkyltrifluoroborates with two different electron-deficient alkenes has been developed. The addition reaction occurs sequentially with α,β-unsaturated carbonyl compounds and vinyltriphenylphosphonium bromide in this order to produce α-branched γ-phosphoniocarbonyl compounds. The reaction could be followed by stereoselective Wittig olefination with various aldehydes to afford structurally diverse α-branched γ,δ-unsaturated ketones and esters with a Z-configuration. Mechanistic investigations suggested that boron trifluoride generated from the organotrifluoroborate activates the α,β-unsaturated carbonyl compound to facilitate the first chemoselective radical addition. We assume that the high efficiency of the second addition with the vinylphosphonium salt might arise from electrostatic interactions caused by the positive charge of the phosphonio group.

The nickel-catalyzed reductive olefin hydrocarbonation reaction is one of the powerful tools for the formation of C(sp³)–C bonds. However, the reductive coupling of alkenes with benzyl halides to afford alkyl–benzyl products has rarely been studied using the well-established Ni/SiH methods. Herein, we report a method of Ni-catalyzed regioselective hydrobenzylation of unactivated alkenes to afford anti-Markovnikov products using BH₃ as a reductant. This method exhibits good functional group tolerance, a wide scope and high regioselectivity. The mild conditions enable the coupling of terminal and internal alkenes with primary and secondary benzyl halides.

The development and applications of novel synthetic intermediates are essential for synthetic chemistry. α-Amino alkyl radicals have been proven to be promising synthetic intermediates for the construction of versatile natural products and drugs. However, high reduction potentials of imines and further oxidation of the generated α-amino alkyl radicals limit their applications. Herein, we reveal the highly selective generation of p-(N,N-dimethyl)benzyl equivalents from easily-available N,N-dimethyl arylamines via α-amino alkyl radicals in the presence of the iridium photosensitizer without any other additives. A series of trifluoromethyl-containing diarylalkanes were obtained in good to high yields from the visible-light-promoted reaction of N,N-dimethyl arylamines and quinols under very mild reaction conditions. The route provides novel access to trifluoromethyl-containing arenes under environment-friendly conditions.

The well-developed carbonylative synthesis of varied and useful complex molecules with CO is very efficient and attractive. Herein, rhodium-catalyzed modular carbonylative aminobenzoylation of alkenes with a pendant acylaniline enabled by dual cleavage of N–H bonds and C–H bonds under ambient pressure of CO/O₂ was developed. Various poly(hetero)cyclic alkylarylketones were obtained in moderate-to-high yields. The logical synthetic transformations of products were also explored.

An efficient and novel method has been developed for the synthesis of indazole-containing biheteroaryls via a domino Sonogashira coupling/azaenyne cycloisomerization/Barton–Kellogg reaction. The new scalable protocol leads to a broad array of substituted indazole-containing biheteroaryls under mild reaction conditions. Compared to classical domino Sonogashira coupling/cyclization, this powerful strategy enables simultaneous generation of two heterocycles, especially the two C-atoms of a terminal alkyne are, respectively, incorporated into two different rings. Preliminary mechanistic studies demonstrate that the CuI catalyst has multiple roles, guaranteeing the connection of each reaction smoothly. Remarkably, this work represents an unprecedented example of domino Sonogashira coupling/metal carbene-involved annulation.

In this article, we disclose a method for the regiodivergent and stereoselective hydrosilylation of isoprene using an Earth-abundant cobalt catalyst via variation of ligands. With a less sterically hindered bidentate ligand, the reactions proceeded through 4,1-hydrosilylation to afford allylsilanes in excellent regio- and stereoselectivities. By switching to a bulkier ligand, the reactions were efficiently diverted to 2,1-addition products for the first time. This regiodivergent protocol provides a modular approach for the construction of structurally diverse organosilanes with high atom economy and without the formation of stoichiometric byproducts.

As an essential van der Waals interaction, the dispersion interaction is an important weak attractive interaction. However, the influence of the weak attractive interactions has only recently been elucidated in transition metal catalyzed asymmetric hydrogenations by the Wanbin Zhang group. Our IGM/EDA analysis proves Zhang's finding that attractive interactions play an important role in asymmetric hydrogenation, which provides new strategies for the sophisticated design of chiral transition metal catalysts. The dispersion interaction is the major weak attractive interaction that activates the asymmetric hydrogenations by favorable interactions of substrate and metal catalyst.

Heteroatom-containing motifs are one of the most privileged scaffolds for pharmaceuticals, agrochemicals, and functional materials. Transition-metal-catalyzed carbon–heteroatom bond-forming reactions have emerged as an indispensable synthetic tool for the rapid assembly of these valuable skeletons. Despite impressive progress, the development of general and efficient methods for the catalytic construction of carbon–heteroatom bonds with Earth-abundant catalysts under mild conditions is still highly desirable. Utilizing the new and unique reactivity uncovered by photoexcitation, recently, exciting progress has been made in the area of visible-light-driven nickel-catalyzed carbon–heteroatom bond-forming reactions, enabling facile access to diverse carbon–heteroatom bonds under exceptionally mild conditions. In this review, we highlight the recent synthetic methodology development for the formation of C–N and C–O bonds via visible-light-driven high-valent nickel complexes or photoexcited nickel complexes, with in-depth discussions with reaction designs and mechanistic scenarios.