Search

Compared with the well-developed centrally chiral boron chemistry, C-B axially chiral chemistry remains elusive and challenging. Herein we report the first atroposelective Miyaura borylation of bromoarenes with unsymmetrical diboron reagents for the direct catalytic synthesis of optically active atropisomeric arylborons. This reaction features broad substrate scope and produces axially chiral arylborons with high yields and good enantioselectivities.

Inspired by the body circulation of Omeprazole (irreversible proton pump inhibitor), we disclose the carbene-triggered cascades for the synthesis of 2-aminobenzofuran derivatives from N-sulfonyl-1,2,3-triazoles or benzothioazole-bearing thiocarbamates, which represents an unprecedented imine derivative migration process. Furthermore, the desulfurizing reagent-free Barton-Kellogg-type reactions starting from N-sulfonyl-1,2,3-triazoles have also been achieved for the first time, and elemental sulfur is confirmed as a byproduct during this transformation. Both experimental data and DFT calculations further thoroughly explained the unique reactivity.

A novel diethylzinc-mediated radical 1,2-addition of perfluoroalkyl iodides to unactivated alkenes and alkynes is presented, which demonstrates a novel way to generate an ethyl difluoroacetate radical. This method is highly efficient and gives full conversions of the substrates, high yields of the products, and negligible byproducts and requires no column chromatography purifications. The mild conditions enable this protocol to exhibit excellent functional group compatibility.

We disclose a novel Pd-catalyzed assembly of fluoren-9-ones by merging of C-H activation and difluorocarbene transfer. ClCF2COONa served as a difluorocarbene precursor to be harnessed as a carbonyl source in this transformation. The current protocol enables us to afford fluoren-9-ones in high yields with excellent functional group compatibility, which also represents the first example of using difluorocarbene as a coupling partner in transition-metal-catalyzed C-H activation.

Multicomponent reactions (MCRs) facilitate the rapid and diverse construction of molecular scaffolds with modularity and step economy. In this work, engagement of boronic acids as carbon nucleophiles culminates in a Passerini-type three-component coupling reaction towards the synthesis of an expanded inventory of α-hydroxyketones with skeletal diversity. In addition to the appealing features of MCRs, this protocol portrays good functional group tolerance, broad substrate scope under mild conditions and operational simplicity. The utility of this chemistry is further demonstrated by amenable modifications of bioactive products and pharmaceuticals as well as in the functionalization of products to useful compounds., Multicomponent reactions enable the rapid construction of diverse molecular scaffolds with modularity and step economy. In this work, the authors report the use of boronic acids as carbon nucleophiles in a Passerini-type three-component coupling reaction towards an expanded inventory of α-hydroxyketones.

Presented herein is the first 1,6-conjugate addition of diborylmethane, which is promoted by a simple and inexpensive copper catalytic system. This method features high yields, good selectivities and broad functional group compatibilities.

Divergent synthesis for precise constructions of cyclic unsymmetrical diaryl disulfides or diselenides and polythiophenes from CF3 -containing 1,3-enynes and S8 was developed when the ortho group is F, Cl, Br, and NO2 on aromatic rings. Meanwhile, disulfides (diselenides) were also quickly constructed when the ortho group is H. These transformations undergo cascade thiophene construction/selective C3-position thiolation process, featuring simple operations, divergent synthesis, broad substrate scope, readily available starting materials, and valuable products. A novel plausible radical annulation process was proposed and validated by DFT calculations for the first time. A series of derivatizations about the thiophene (TBT) and disulfides were also well-represented.

Summary CF3-containing multi-borylated compounds are intriguing molecules that can serve as building blocks and readily transform into various significant molecules. Here, a series of Cu-catalyzed assembly of 1,3- and 1,4-diborylated compounds bearing CF3 group starting from readily available 1,3-enynes has been developed. This is the first example that could approach two different C–B bonds from 1,3-enynes despite their conjugated structures. The unprecedented regio- and stereodivergent sp2/sp3 1,3- and 1,4-diborylations of 1,3-enynes were regulated by ligands, bases, and solvents. Most remarkably, the well-known defluorination of CF3 group on alkenes upon nucleophilic additions was completely suppressed in our systems, leaving a valuable CF3 group intact. Moreover, homopropargylic boronates and homoallenyl boronates as the key intermediates for the above transformations were also obtained after fine-tuning the reaction conditions. Both experimental and theoretical calculations elucidate the E/Z selectivities and regioselectivities in these transformations.

Transition-metal- or oxidant-promoted deconstructive functionalizations of noncyclic carbon–nitrogen bonds are well established, usually only leaving one moiety functionalized toward the final product. In contrast, concomitant C- and N-functionalizations via the unstrained C(sp3)–N bond under metal- and oxidant-free conditions are very rare, which would favorably confer versatility and product diversity. Disclosed herein is the first difluorocarbene-induced deconstructive functionalizations embodying successive C(sp3)–N bond cleavage of cyclic amines and synchronous functionalization of both constituent atoms which would be preserved in the eventual molecular outputs under transition-metal-free and oxidant-free conditions. Correspondent access to deuterated formamides with ample isotopic incorporation was demonstrated by a switch to heavy water which is conceivably useful in pharmaceutical sciences. The current strategy remarkably administers a very convenient, operationally simple and novel method toward molecular diversity from readily available starting materials. Therefore, we project that these findings would be of broad interest to research endeavors encompassing fluorine chemistry, carbene chemistry, C–N bond activation, as well as medicinal chemistry., Difluorocarbene-induced C(sp3)−N bond cleavage of tertiary amines is disclosed under transition-metal-free and oxidant-free conditions for the first time, leading to versatile functionalized products.

The first copper-catalyzed atroposelective Michael-type addition between azonaphthalenes and arylboronic acids for the construction of biaryl atropisomers was established using a novel BINOL-derived phosphoramidite as a chiral ligand. A broad range of atropisomeric biaryls were obtained with good efficiency, and the practicality of this approach was verified by versatile transformations toward axially chiral ligands, catalysts, and other functional atropisomers. This set of catalytic systems successfully inhibited the routine 1,2-addition and promoted the formation of an aryl-aryl chiral axis. Meanwhile, this strategy bypassed the use of an oxidant as well as the harsh conditions normally necessary for transition-metal-mediated arene C-H coupling with arylboronic acids as an arylation counterpart, offering a straightforward alternative to access optically active biaryls.

A new chiral Brønsted acid, generated in situ from a chiral phosphoric acid boron (CPAB) complex and water, was successfully applied to asymmetric indole reduction. This "designer acid catalyst", which is more acidic than TsOH as suggested by DFT calculations, allows the unprecedented direct asymmetric reduction of C2-aryl-substituted N-unprotected indoles and features good to excellent enantioselectivities with broad functional group tolerance. DFT calculations and mechanistic experiments indicates that this reaction undergoes C3-protonation and hydride-transfer processes. Besides, bulky C2-alkyl-substituted N-unprotected indoles are also suitable for this system.

A divergent strategy for precise construction of SCF2H or SeCF2H groups on heteroarenes generated in situ from CF3-containing 1,3-enynes was developed. Reactions of readily available 1,3-enynes wit...

We present a novel Cu-catalyzed aromatic metamorphosis of 3-aminoindazoles via oxidative cleavage of two C-N bonds of 3-aminoindazoles. This unprecedented reactivity of 3-aminoindazoles allows one to forge diverse nitrile-containing triphenylenes in decent yields via generation of the cyano group

A tert-butyl nitrite (TBN)-mediated synthesis of fluorinated O-alkyloxime ether derivatives with bromodifluoroalkyl reagents as the fluorine sources has been developed. A variety of halodifluorinated compounds were found compatible, delivering the desired products in moderate to excellent yields. This transformation features a simple operation, can be done in air, and found to involve radicals. This protocol represents a straightforward approach to access various fluorinated O-alkyloxime ether derivatives.

We disclose a novel Cu-catalyzed denitrogenative transannulation of 3-aminoindazoles to afford diverse functionalized 3-aminobenzothiophenes and 1-aminoisoquinolines, in which denitrogenative transannulation of 3-aminoindazoles is reported for the first time. This transformation proceeds via an “extrude-and-sew” strategy with an unprecedented radical reactivity of 3-aminoindazoles.

Reported herein is a stereospecific 1,4-metallate rearrangement for single-geometry ketoxime synthesis from oxime chlorides and arylboronic acids. This strategy exhibits broad substrate scope with excellent stereoselectivity under mild reaction conditions. In comparison with the conventional approaches, each configuration of unsymmetric diaryl oximes, as well as the thermodynamically less stable Z isomer of aryl alkyl ketoximes can be selectively and exclusively obtained. The reactivities of unsymmetric diaryl oximes and the Z isomer of aryl alkyl oximes, a class of underexplored molecules, enables efficient access to the corresponding isoquinolines, isoquinoline N-oxides, and amides having a single configuration.

We have presented a simple and new method for the divergent assembly of furoxans and isoxazoles in which the [2 + 1 + 1 + 1] annulation reaction of sulfoxonium ylides is reported for the first time. When the reaction was performed using tBuONO as the nitrogen source without metal catalyst, the desired furoxans were obtained in decent yields with wide substrate scope. Isoxazoles bearing three carbonyl groups were achieved when the reaction was conducted using Cu(TFA)2 as catalyst.

A radical-promoted cyclization of methylthiolated alkynones with diverse radical precursors has been developed. This strategy occurred via a C(sp2)–S bond formation and C(sp3)–S cleavage sequence and allows an efficient synthesis of a variety of phosphoryl-, sulfenyl-, CF2COOEt-, and acyl-containing thiochromone derivatives in moderate to good yields under mild conditions.

An efficient transition metal-free annulation of amidine with ethyl bromodifluoroacetate to access 2,4-disubstituted-1,3,5-triazines is firstly presented. The desired symmetric and unsymmetric 2,4-disubstituted-1,3,5-triazines were obtained in decent yields via multiple C-N bond formation, in which ethyl bromodifluoroacetate is harnessed as a unique C1 synthon via quadruple cleavage. This reaction is transition metal-free, oxidant-free and simple in operation, and only lowly toxic inorganic wastes are generated.

The oxidant-controlled divergent reactivity of 3-aminoindazoles is presented herein. Diverse functionalized pyrimido[1,2-b]-indazole derivatives were obtained with good yields via a Lewis-acid promoted [3 + 3] annulation reaction between ketene dithioacetals and 3-aminoindazoles. When the reaction was performed using the Cu/[O] catalytic system, new reactivity for the ring-opening of 3-aminoindazoles via C–N bond activation was achieved, which enables the olefinic C–H arylation of ketene dithioacetals under mild conditions.

An oxidative cyclization of β,γ-unsaturated hydrazones for the divergent assembly of pyrazolones and pyrazolines under metal-free conditions is presented. This divergent synthetic strategy was achieved by controlling the reaction atmosphere. A number of pyrazolines were obtained via 5-exo-trig cyclization when the reaction was performed under N2. Whereas when the reaction was conducted under O2, diverse functionalized pyrazolones were achieved via oxidative cleavage of the CC double bond.

The transition-metal-catalyzed allylation reaction is an efficient strategy for the construction of new carbon-carbon bonds alongside allyl or homoallylic functionalization. Herein we describe a Ni-catalyzed reductive allylation of α-chloroboronates to efficiently render the corresponding homoallylic boronates, which could be readily converted into valuable homoallylic alcohols or amines or 1,4-diboronates. This reaction features a broad substrate scope with good functional group compatibility that is complementary to the existing methods for the preparation of homoallylic boronates.

ConspectusOrganoboron compounds are a class of multifunctional reagents for the construction of carbon-carbon and carbon-heteroatom bonds in modern synthetic chemistry. The transformations of organoboron compounds are usually carried out through tetracoordinate boron intermediates and mainly include additions to unsaturated bonds, rearrangement reactions, transmetalation reactions, and so on. Although great progress has been achieved in improving tetracoordinate boron intermediates, there are still shortcomings, such as sparse activation modes, a paucity of reaction strategies and difficulties in stereoselective control. In this Account, we mainly discuss our recent advances in the development of unconventional transformations of organoboron compounds based on the design of tetracoordinate boron intermediates, including the following three topics: (1) the construction of C-B bonds; (2) the construction of C-C bonds; (3) the design and application of chiral tetracoordinate boron.The development of new strategies to build C-B bonds is of great interest for chemists. We have developed tandem reactions involving multiple tetracoordinate boron intermediates for the selective borylations of alkynes and the synthesis of stable tetracoordinate boron, including a domino-borylation-protodeboronation (DBP) strategy for selective borylations of alkynes, highly regio-, stereo-, and chemoselective Cu-catalyzed diborylation of β-CF3-1,3-enynes and cascade B-Cl/C-B cross-metathesis and C-H bond borylation for the synthesis of tetracoordinate triarylboranes. We have also developed novel strategies involving tetracoordinate boron intermediates to form C-C bonds because the formation of C-C bonds is an enduring theme of organic chemistry. We disclosed long distance or multiple migration reactions and novel coupling partners in transmetalation reactions, such as long distance 1,4-migrations of tetracoordinate nitrile oxide boron and nitrilium boron intermediates, multiple migrations of tetracoordinate isocyanide boron intermediate, palladium-catalyzed Suzuki-Miyaura coupling of thioureas or thioamides, copper-catalyzed atroposelective Michael-type addition, and a palladium-catalyzed atroposelective Catellani reaction. Moreover, in terms of stereoselective control of the tetracoordinate boron intermediate, we found that a chiral tricoordinate boron complex could activate water to form a chiral tetracoordinate boron complex with Bronsted acidity, which has been successfully applied with high enantioselectivity to the asymmetric catalytic reduction of challenging indoles.This Account summarizes our recent efforts using unconventional transformations of organoboron compounds for the design of tetracoordinate boron intermediates, which not only achieved the precise construction of a wide range of diverse C-B bonds and C-C bonds but also developed a novel chiral Bronsted acid for the asymmetric catalytic reduction of challenging indoles.

A three-component strategy for the synthesis of thiazoles and isothiazoles has been developed by employing enaminoesters, fluorodibromoiamides/ester, and sulfur. The thiazoles and isothiazoles were formed via two C-F bond cleavages along with the formation of new C-S, C-N, and N-S bonds. The strategy provides high selectivity for the synthesis of thiazoles/isothiazoles, which have vital applications in drug discovery and development.

An expedient strategy for the synthesis of 5-oxazole ketones was developed via homogeneous gold catalysis with 4-MeO-TEMPO as an oxidant. The desired 5-oxazole ketones were achieved in decent yields with an excellent functional group compatibility under mild conditions. The current protocol also represents the first example for merging a gold catalyst and radical chemistry in one-pot synthesis with internal N-propargylamides.

An efficient approach to tetrasubstituted alkenylboronates via a cascade borylation/B–O elimination of propynols and B2pin2 was disclosed. A series of tetrasubstituted alkenylboronates were readily furnished with this strategy in good yields, with further transformations leading to tetrasubstituted alkenes and β-diketones demonstrating the synthetic potential of the alkenylboronates constructed by this strategy as versatile intermediates in organic synthesis.

This review summarizes the very recent advances in asymmetric reactions catalyzed by chiral phosphoric acids (CPAs), a family of versatile catalysts that catalyze a broad range of reactions to afford diverse chiral molecules. In the past years, different kinds of chiral phosphoric acids have been designed and developed into a privileged class of catalysts in asymmetric synthesis. A number of remarkable achievements have been made by many groups around the world. Due to length limitation, this review only summarizes those works published from January 2016 to November 2017. Meanwhile, catalytic systems which combine metal catalysts and chiral phosphoric acids will not be discussed in this review.

A direct strategy for intramolecular transfer oxygenation of alkynes and cycloisomerization of 2-nitroalkynes to synthesize a wide range of C2-quaternary indolin-3-ones was developed by a copper/diboron system. The desired allylation, benzylation and propargylation products were obtained in moderate to excellent yields with good functional group tolerance. The mechanism study indicated that this protocol involved a radical process.

An expedient and mild strategy for the synthesis of unconventional 2-(dimethylamino)-3,3-difluorochroman-4-one derivatives from o-hydroxyarylenaminones and Selectfluor was developed at room temperature under catalyst-free conditions. This method showed excellent chemoselectivity and great functional groups tolerance.

An environmentally benign and convenient method is developed to access a variety of functionalized geminal-diborylalkanes from various electron-deficient alkynes and B2pin2. The reactions proceed via the Domino-Borylation–Protodeboronation (DBP) strategy under mild conditions with high regioselectivity, high chemoselectivity, broad functional group tolerance as well as high yields. Meanwhile, further applications of the gem-diboronate products have been explored by silver-catalyzed deboronation–difluorination, base-mediated protodeboronation as well as deborylative secondary alkylation of 2-phenylpyridine N-oxides.

A photoredox-catalyzed cascade annulation of methyl(2-(phenylethynyl)phenyl)sulfanes and methyl(2-(phenylethynyl)phenyl)selanes with sulfonyl chlorides was developed. A variety of benzothiophenes and benzoselenophenes were obtained in moderate to good yields at ambient temperature.

A rhodium-catalyzed selective deesterification and decarbonylation of diazo compounds is presented. Various α-aryl ketones and esters could be obtained in good to excellent yields with a wide substrate scope using benzimidazoles as the directing groups. Dual C–H activation products can also be gained by one-pot C–H functionalization/cyclization, using excess diazo compounds.

To develop a simple and efficient synthetic method for four-coordinate triarylboranes, we herein describe a tandem highly selective B–Cl/C–B cross-metathesis of two of the same or different arylboranes and C–H bond borylation to synthesize four-coordinate triarylboranes with a broad substrate scope. By switching substituent groups of the target molecules, different emission wavelengths can be achieved from 467 nm to 583 nm with aggregation-induced emission (AIE) properties.

An expedient and efficient strategy was developed for the synthesis of benzimidazole derivatives from aryne precursors with CsF and K2CO3 under transition metal-free conditions. The reaction exhibited good functional group tolerance, as substrates containing alkyls, ethers, nitryls, halogens etc., could all undergo the reaction smoothly, and afforded the desired products in good to excellent yields.

We herein disclose a Cu-catalyzed synthesis of 5-arylsubstituted 1,2,3-triazoles via an oxidative interrupted click reaction, using air as the sole terminal oxidant. The current protocol provides a novel method for the one-step construction of fully substituted triazoles in good yields under mild conditions, in which arylboronic acids are employed as aromatic sources to interrupt the cuprate–triazole intermediate for the first time.

The first oxidative ring-opening of 3-aminoindazoles based on N–N bond cleavage is reported herein. A variety of 2-aminobenzoates were obtained in good yields under mild conditions, in which the free, mono- and dual-brominated aminobenzoates could be controllably achieved by employing the appropriate oxidant and bromine source.

An anti-Markovnikov hydroarylation of unsaturated amides via a Cu/Pd synergistically catalyzed cascade borylation/intramolecular sp2–sp3 cross-coupling has been disclosed. 3,4-Dihydroquinolinones, one type of important scaffold prevailing in pharmaceuticals and biologically active compounds, could be readily accessible with high regio-selectivity and high yields.

An efficient one-pot cascade process via unprecedented quadruple cleavage of BrCF2COOEt with primary amines to afford valuable fluorine-containing heterocycles is described, in which BrCF2COOEt plays a dual role as a C1 synthon and a difluoroalkylating reagent for the first time. Mechanistic studies supported by DFT calculations suggest that a base plays an active role in the formation of the key intermediate isocyanides generated in situ from primary amines and difluorocarbene.

An expedient strategy of reductive N-alkylation of amines with readily available carboxylic acids as alkylating reagents has been developed. Commercially available and hydrogen rich ammonia borane (H3B·NH3) was employed as a practical hydrogen source. Mono- and dialkylated products of primary amines could be selectively obtained by varying the reaction conditions. Complementary to known reductive aminations, this strategy showed excellent functional group compatibility, and a broad range of secondary and tertiary amines, including drug molecules, were obtained smoothly.

A highly efficient synthesis of 3-formyl imidazo[1,2-a]pyridine and imidazo[1,2-a]pyrimidine, under Cu-catalyzed aerobic oxidative conditions and by utilizing ethyl tertiary amines as carbon sources, is disclosed. A novel activation mode of ethyl tertiary amines in which simultaneous selective cleavage of C-C bond and C-N bond of ethyl group with molecular oxygen as terminal oxidant in this one-pot protocol is reported for the first time. This reaction features broad substrate scope, good functional group tolerance, as well as diversified and valuable products.

A novel copper(I)-catalyzed chemoselective reduction of the carbonyls of benzofuran-2-yl ketones over furan rings with B2pin2 has been developed. This reaction proceeded under mild conditions. High valuable secondary alcohol derivatives of benzofurans were obtained in good to excellent yields with a broad substrate scope. The mechanistic studies suggested that a domino-borylation-protodeboronation pathway was involved in this reaction.

An efficient and convenient synthesis of valuable disulfanes and benzenesulfonothioates, having a 2-aminofuran framework, has been developed by employing a copper-catalyzed transformation of readily available N-tosylhydrazone-bearing thiocarbamates. This method features an inexpensive metal catalyst, mild reaction conditions, good functional-group tolerance, short reaction times, and delivers valuable and complex products. A copper carbene generated from an N-tosylhydrazone-bearing thiocarbamate is proposed as the key intermediate for the transformation and it triggers the subsequent cascade. Remarkably, the Ts anion released from N-tosylhydrazone further serves as a nucleophile, thus rendering the formation of benzenesulfonothioates under controlled conditions.

A Pd(II)-catalyzed ortho-olefination of aromatic acetic esters is described which features with an excellent funcitional group tolerance, good yields, mild reaction conditions, good scalability as well as high chemo- and regio-selectivity.

A direct and single-step procedure towards substituted pyrimidine and pyridine derivatives via Lewis acid-promoted [3+3] annulation between 3-ethoxycyclobutanones and enamines or amidines is presented. Diverse substituted pyrimidine and pyridine derivatives were obtained in good to high yields with a wide substrate scope.

An original and efficient copper-catalyzed 1,6-hydrodifluoroacetylation of para-quinone methides with difluoroalkyl bromides has been described with bis(pinacolato)diboron (B2pin2) as reductant. In this reaction, a new C(sp3)–CF2 bond is constructed under smart conditions. A broad substrate scope of para-quinone methides (p-QMs) make this protocol very practical and attractive. Preliminary mechanistic studies manifested that a difluoroalkyl radical pathway was involved in this reaction. Also the presence of the diboron reagent was an essential requisite in this transformation.

An unconventional reductive quenching cycle was developed to realize the visible-light-induced thiotrifluoromethylation of terminal alkenes. CF3SO2Na was used as an easy to handle CF3 radical source to afford the desired products in moderate to good yields. Mild reaction conditions and a broad substrate scope feature in this transformation.

An original and efficient synthesis of 3,3-difluoro-2-oxindole derivatives has been developed via copper/B2pin2-catalyzed difluoroacetylation of aniline via C–H activation followed by intramolecular amidation. In this method, amino groups in primary, secondary or tertiary anilines act as directing groups, providing ortho-difluoroacetylated products regioselectively. And in the first two cases, further intramolecular amidation affords 3,3-difluoro-2-oxindole derivatives via a one-pot strategy. This method facilitates the synthesis of compound A as a potent and selective EP3 receptor antagonist in only five steps in 13% yield instead of the previously reported nine steps in overall 4% yield.

H2O is routinely described as a proton donor, however, in the presence of diboron compounds, the umpolung reaction of H2O under metal-free conditions was successfully developed, which could afford hydride species, leading to a highly efficient and chemoselective reduction of CO bonds. This strategy exhibits excellent chemoselectivities toward carbonyl groups in the presence of ester, olefin, halogen, thioether, sulfonyl, cyano as well as heteroaromatic groups.

Transition-metal-free base-controlled highly regioselective synthesis of alkyl 1,2-bis(boronates) or 1,1,2-tris(boronates) from various terminal alkynes has been disclosed. These reactions are efficient, practical and mild with good regioselectivity, excellent functional group tolerance as well as good scalability, which provide general and complementary methods to access multiborylated alkanes from various terminal alkynes.