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An efficient and broadly applicable rhodium‐catalyzed direct ortho‐arylation of anilines with aryl iodides relying on readily available aminophosphines as traceless directing groups is reported. Its scope and functional group compatibility were both found to be quite broad as a large variety of both aminophosphines and (hetero)aryl iodides, including complex ones, could be utilized. The ortho‐arylated anilines could be obtained in high average yields, without any competing diarylation and with full regioselectivity, which constitutes a major step forward compared to other processes. The reaction is moreover not limited to aryl iodides, as an aryl bromide and a triflate could be successfully used, and could be extended to diarylation. Mechanistic studies revealed the key and unique role of the aminophosphine, acting not only as a substrate but also as a ligand for the rhodium catalyst. [ABSTRACT FROM AUTHOR]

Geminal bis(boronates) are versatile synthetic building blocks in organic chemistry. The fact that they predominantly serve as nucleophiles in the previous reports, however, has restrained their synthetic potential. Herein we disclose the ambiphilic reactivity of α‐halogenated geminal bis(boronates), of which the first catalytic utilization was accomplished by merging a formal Heck cross‐coupling with a highly diastereoselective allylboration of aldehydes or imines, providing a new avenue for rapid assembly of polyfunctionalized boron‐containing compounds. We demonstrated that this cascade reaction is highly efficient and compatible with various functional groups, and a wide range of heterocycles. In contrast to a classical Pd(0/II) scenario, mechanistic experiments and DFT calculations have provided strong evidence for a catalytic cycle involving Pd(I)/diboryl carbon radical intermediates. [ABSTRACT FROM AUTHOR]

Boronate rearrangements, such as the Matteson and Petasis reactions, are valuable metal‐free reactions for the transfer of the carbo group on boron to intramolecular electrophilic sites. However, only highly reactive electrophiles are suitable, and ketones are too inactive for those boronate rearrangements due to the high energy barriers. We disclose here the 1,3‐boronate rearrangement to ketones, for which a high energy barrier (44.9 kcal/mol) is prohibitory for thermal reactions in the ground state. The reaction is enabled by the key keto‐enol‐boronate bidentate complex formation in situ, which absorbs visible light to reach the excited state for the chemoselective 1,3‐boronate rearrangement to ketones. Experimental and computational investigations exclude free radical intermediates from organoboronates. The aryl, alkenyl, and alkyl boronic acids react with various 1,3‐diketones driven by visible light irradiation to construct structurally diverse β‐keto tertiary alcohols under metal‐free conditions. The reaction demonstrates substrate diversity with 58 examples, yields up to 98 %, and it is suitable for gram‐scale synthesis. [ABSTRACT FROM AUTHOR]

Featuring the simultaneous generation of a library of compounds from a certain intermediate, divergent synthesis has found increasing applications in the construction of natural products and potential medicines. Inspired by this approach, presented herein is a general strategy to introduce functionality, in a divergent manner, into covalent organic frameworks (COFs). This modular protocol includes two stages of covalent assembly, through which functional COFs can be constructed by a three‐step transformation of a key platform molecule, such as 4,7‐dibromo‐2‐chloro‐1H‐benzo[d]imidazole (DBCBI). Constructed herein are four types of chiral COFs (CCOFs) from DBCBI by nucleophilic substitution, Suzuki coupling, and imine formation. The unique array of eight isoframework CCOFs allowed investigation of their catalytic performance and structure–activity relationship in an asymmetric amination reaction. [ABSTRACT FROM AUTHOR]

Carboxylation of easily available alkenes with CO2 is highly important to afford value‐added carboxylic acids. Although dicarboxylation of activated alkenes, especially 1,3‐dienes, has been widely investigated, the challenging dicarboxylation of unactivated 1,n‐dienes (n>3) with CO2 remains unexplored. Herein, we report the first dicarboxylation of unactivated skipped dienes with CO2 via electrochemistry, affording valuable dicarboxylic acids. Control experiments and DFT calculations support the single electron transfer (SET) reduction of CO2 to its radical anion, which is followed by sluggish radical addition to unactivated alkenes, SET reduction of unstabilized alkyl radicals to carbanions and nucleophilic attack on CO2 to give desired products. This reaction features mild reaction conditions, broad substrate scope, facile derivations of products and promising application in polymer chemistry. [ABSTRACT FROM AUTHOR]

The aldehydes installation by radical formylation constitutes an attractive synthetic strategy. However, the generation of formyl radicals for organic synthesis applications remains unknown. Herein we report the first formyl radical generation from α‐chloro N‐methoxyphthalimides, which selectively synthesize aldehydes by alkene hydroformylation under mild photoredox conditions. The aldehydes can be installed on acrylates, acrylamides, vinyl sulfones, vinyl ketones, and complex steroids by radical hydroformylation in excellent chemoselectivity and regioselectivity. The concerted hydrochloride elimination for the formyl radical generation from α‐chloro methoxy radicals is established by experimental and computational approaches. [ABSTRACT FROM AUTHOR]

Silanes are important in chemistry and material science. The self‐redistribution of HSiCl3 is an industrial process to prepare SiH4, which is widely used in electronics and automobile industries. However, selective silane cross‐redistribution to prepare advanced silanes is challenging. We now report an enthalpy‐driven silane cross‐redistribution to access bis‐silanes that contain two different types of Si−H bonds in the same molecule. Compared with entropy‐driven reactions, the enthalpy‐driven reaction shows high regioselectivity, broad substrate scope (62 examples) and high atom economy. Our combined experimental and computational study indicates that the reaction proceeds through a Ni0‐NiII‐NiIV catalytic cycle. [ABSTRACT FROM AUTHOR]

Silaspiranes have attracted particular attention due to their chiral spiro‐silicon center, which serves as an ideal carbon isostere and can endow spiro‐analogs with distinct properties. Distinct from previously reported cyclization or cycloaddition strategies to form 5/5‐silaspiranes, we report herein the asymmetric dual ring expansion of spirosilabicyclobutanes with alkynes to synthesize axially chiral spirosilabicyclohexenes bearing a novel 6/6‐silaspirane framework. DFT (density functional theory) calculations provide the deep insight into the origin of the high enantioselectivity controlled by the sterically demanding binaphthyl phosphoramidite ligand. Preliminary studies of chiroptical properties indicate that one of the spirosilabicyclohexene analogs exhibit fluorescence emission, Cotton effects and CPL (circularly polarized luminescence) activity. [ABSTRACT FROM AUTHOR]

Both aryne 1,4‐disubstitution and 1,2,4‐trifunctionalization were accomplished from tertiary amines bearing a penta‐2,4‐dien‐1‐yl moiety. These transformations could directly incorporate a C−N and a C−C bond para to each other on an aryne intermediate via a sequential nucleophilic addition and [5,5]‐sigmatropic rearrangement. When arynes bearing 3‐tethered electrophiles were employed, a cascade regioselective nucleophilic addition, intramolecular cyclization, and remote diastereoselective [5,5]‐sigmatropic rearrangement process was observed. Our density functional theory (DFT) calculations revealed that hydrogen‐bonding interactions between two C−H hydrogens on the penta‐2,4‐dien‐1‐yl chain and the oxygen anion generated upon N‐nucleophilic annulation reaction in the [5,5]‐sigmatropic rearrangement step is responsible for the remote diastereoselective control in this reaction system. [ABSTRACT FROM AUTHOR]

C‐Acyl glycosides are versatile intermediates to natural products and medicinally relevant entities. Conventional cross‐coupling strategies to secure these molecules often relied on two‐component manifolds in which a glycosyl precursor is coupled with an acyl donor (pre‐synthesized or generated in situ) under transition metal or dual catalysis to forge a C−C bond. Here, we disclose a three‐component Ni‐catalyzed reductive regime that facilitates the chemoselective union of glycosyl halides, organoiodides and commercially available isobutyl chloroformate as a CO surrogate. The method tolerates multiple functionalities and the resulting products are obtained in high diastereoselectivities. Theoretical calculations provide a mechanistic rationale for the unexpectedly high chemoselectivity of sequential cross‐electrophile couplings. This approach enables the expeditious assembly of difficult‐to‐synthesize C‐acyl glycosides, as well as late‐stage keto‐glycosylation of oligopeptides. [ABSTRACT FROM AUTHOR]

A catalytic 1,2‐oxyhalogenation method that converts non‐conjugated internal alkynes into tetrasubstituted alkenes with high regio‐ and stereoselectivity is described. Mechanistically, the reaction involves a PdII/PdIV catalytic cycle that begins with a directed oxypalladation step. The origin of regioselectivity is the preference for formation of a six‐membered palladacycle intermediate, which is facilitated by an N,N‐bidentate 2‐(pyridin‐2‐yl)isopropyl (PIP) amide directing group. Selectivity for C(alkenyl)−X versus −N (X=halide) reductive elimination from the PdIV center depends on the identity of the halide anion; bromide and iodide engage in C(alkenyl)−X formation, while intramolecular C(alkenyl)−N reductive elimination occurs with chloride to furnish a lactam product. DFT calculations shed light on the origins of this phenomenon. [ABSTRACT FROM AUTHOR]

We herein demonstrated an efficient method for the atroposelective construction of nine‐membered carbonate‐bridged biaryls through vinylidene ortho‐quinone methide (VQM) intermediates. Diverse products with desirable pharmacological features were synthesized in satisfying yields and good to excellent enantioselectivities. In subsequent bioassays, several agents showed considerable antiproliferative activity via the mitochondrial‐related apoptosis mechanism. Further transformations produced more structural diversity and may inspire new ideas for developing functional molecules. [ABSTRACT FROM AUTHOR]

Catalytic asymmetric synthesis of chiral endocyclic allenes remains a challenge in allene chemistry owing to unfavored tension and complex chirality. Here, we present a new relay strategy merging Pd‐catalyzed asymmetric [3+2] annulation with enyne‐Cope rearrangement, providing a facile route to chiral 9‐membered endocyclic allenes with high efficiency and enantioselectivity. Moreover, theoretical calculations and experimental studies were performed to illustrate the critical, but unusual Cope rearrangement that allows for the complete central‐to‐axial chirality transfer. [ABSTRACT FROM AUTHOR]

The stannum–ene reactions of both benzyne and cyclohexyne were realized, which is particularly suitable for cyclohexyne with a broad substrate scope and excellent chemoselectivity. Our DFT calculations via distortion/interaction analysis revealed that both stannum– and hydrogen–ene reactions with cyclohexyne have later transition states due to their higher distortion energies in the transition states than those in benzyne reactions, which lead to enhanced Pauli repulsion as the decisive factor in the interaction energy accompanied with enlarged energy gap between two types of ene reactions. Therefore, excellent chemoselectivity was disclosed in the cyclohexyne–ene reaction. [ABSTRACT FROM AUTHOR]

Considering the ubiquitous nature and ready synthesis of amides, and the great significance of organofluorine‐containing species, the cross‐coupling of amides and polyfluoroarenes, leading to new carbon–carbon bond‐forming methodologies, would find useful applications in synthesis, late‐stage functionalization, and rapid generation of molecular diversity. Herein, we present a novel synthesis of α‐polyfluoroaryl amines via Sm/SmI2‐mediated deoxygenative cross‐coupling of aromatic amides with polyfluoroarenes through direct C−H functionalization. The structural and functional diversity of these readily available precursors provides a versatile and flexible strategy for the streamlined synthesis of α‐polyfluoroaryl amines. Combining experimental and theoretical studies, a novel plausible mechanism of the α‐aminocarbene‐mediated C−H insertion has been revealed, which may stimulate future work for the development of novel methods in amine synthesis. [ABSTRACT FROM AUTHOR]

We present herein our experimental and DFT computational studies on the directing ability of chalcogenoether motifs in Pd‐catalyzed atroposelective C−H functionalization. The thioether motif was found to be a superior directing group compared to the corresponding ether and selenoether in terms of reactivity and enantiocontrol. Remarkably, DFT calculation provided a predictive model for the optimization of reaction conditions and the interpretation of the origin of enantioselectivity. Both Pd‐catalyzed enantioselective C−H olefination and allylation reactions were successfully developed using chiral phosphoric acids as efficient ligands, providing a broad range of axially chiral biaryls in good yields with excellent enantioselectivities. The highly enantio‐ and diastereoselective construction of polyaryls bearing multiple stereogenic axes, gram‐scale reaction and various chemical transformations make this protocol more attractive and significant. [ABSTRACT FROM AUTHOR]

Computations and experiments leading to new chiral phosphoric acids (CPAs) for epoxide thionations are reported. Density functional theory calculations reveal the mechanism and origin of the enantioselectivity of such CPA‐catalyzed epoxide thionations. The calculated mechanistic information was used to design new efficient CPAs that were tested experimentally and found to be highly effective. Bulky ortho‐substituents on the 3,3′‐aryl groups of the CPA are important to restrict the position of the epoxide in the key transition states for the enantioselectivity‐determining step. Larger para‐substituents significantly improve the enantioselectivity of the reaction. [ABSTRACT FROM AUTHOR]

Axially chiral open‐chain olefins represent an underexplored class of chiral platform. In this report, two classes of tetrasubstituted axially chiral acyclic olefins have been accessed in excellent enantioselectivity and regioselectivity via C−H activation of (hetero)arenes assisted by a migratable directing group en route to coupling with sterically hindered alkynes. The coupling of indoles bearing an N‐aminocarbonyl directing group afforded C–N axially chiral acrylamides with the assistance of a racemic zinc carboxylate additive. DFT studies suggest a β‐nitrogen elimination–reinsertion pathway for the directing group migration. Meanwhile, the employment of N‐phenoxycarboxamide delivered C−C axially chiral enamides via migration of the oxidizing directing group. Experiments suggest that in both cases the (hetero)arene substrate adopts a well‐defined orientation during the C−H activation, which in turn determines the disposition of the alkyne in migratory insertion. Synthetic applications of representative chiral olefins are demonstrated. [ABSTRACT FROM AUTHOR]

Axially chiral open‐chain olefins represent an underexplored class of chiral platform. In this report, two classes of tetrasubstituted axially chiral acyclic olefins have been accessed in excellent enantioselectivity and regioselectivity via C−H activation of (hetero)arenes assisted by a migratable directing group en route to coupling with sterically hindered alkynes. The coupling of indoles bearing an N‐aminocarbonyl directing group afforded C–N axially chiral acrylamides with the assistance of a racemic zinc carboxylate additive. DFT studies suggest a β‐nitrogen elimination–reinsertion pathway for the directing group migration. Meanwhile, the employment of N‐phenoxycarboxamide delivered C−C axially chiral enamides via migration of the oxidizing directing group. Experiments suggest that in both cases the (hetero)arene substrate adopts a well‐defined orientation during the C−H activation, which in turn determines the disposition of the alkyne in migratory insertion. Synthetic applications of representative chiral olefins are demonstrated. [ABSTRACT FROM AUTHOR]

Reported herein is the rhodium(III)‐catalyzed C−H activation of anilines bearing an N‐isoquinolyl directing group for oxidative [3+2] annulation with four classes of internal alkynes, leading to atroposelective indole synthesis via dynamic kinetic annulation with C‐N reductive elimination constituting the stereo‐determining step. This reaction proceeds under mild conditions with high regio‐ and enantioselectivity and functional group compatibility. [ABSTRACT FROM AUTHOR]

The non‐noble metal‐catalyzed asymmetric hydrogenation of N‐heteroaromatics, quinolines, is reported. A new chiral pincer manganese catalyst showed outstanding catalytic activity in the asymmetric hydrogenation of quinolines, affording high yields and enantioselectivities (up to 97 % ee). A turnover number of 3840 was reached at a low catalyst loading (S/C=4000), which is competitive with the activity of most effective noble metal catalysts for this reaction. The precise regulation of the enantioselectivity were ensured by a π–π interaction. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

We have rationally designed a new class of alkyne‐tethered oximes and applied them in an unprecedented iron‐catalyzed radical relay protocol for the rapid assembly of a wide array of structurally new and interesting fused pyridines. This method shows broad substrate scope and good functional‐group tolerance and enabled the synthesis of several biologically active molecules. Furthermore, the fused pyridines could be diversely functionalized through various simple transformations, such as cyclization, C−H alkylation, and a click reaction. DFT calculation studies indicate that the reactions involve cascade 1,5‐hydrogen atom transfer, 5‐exo‐dig radical addition, and cyclization processes. Moreover, preliminary biological investigations suggest that some of the fused pyridines exhibit good anti‐inflammatory activity by restoring the imbalance of inflammatory homeostasis of macrophages in a lipopolysaccharide‐induced model. [ABSTRACT FROM AUTHOR]

An efficient cascade reaction of tryptamine‐derived isocyanides with C,N‐cyclic azomethine imines is described. The polycyclic pyrrolo[2,3‐c]quinoline derivatives, which benefited from rearrangement process driven by hydrogen bonding, could be directly assembled in moderate to good yields (40–87 %) under metal‐free and mild conditions. This transformation involved four new heterocyclic rings formations and uniquely, ring opening of indole as well as ring expansion of C,N‐cyclic azomethine imine. Both experimental and DFT studies provided guidance on the in‐depth insight into the reaction pathways and hydrogen bonding was identified to lower the free energy barrier in transition states. This work constitutes a rare example of tryptamine‐derived isocyanide‐based cascade reactions, and potentially could be a powerful synthetic strategy for accessing polycyclic analogues involved in natural products. [ABSTRACT FROM AUTHOR]

Remote difunctionalization of unactivated alkenes is challenging but a highly attractive tactic to install two functional groups across long distances. Reported herein is the first remote difunctionalization of alkenes with CO2. This visible‐light photoredox catalysis strategy provides a facile method to synthesize a series of carboxylic acids bearing valuable fluorine‐ or phosphorus‐containing functional groups. Moreover, this versatile protocol shows mild reaction conditions, broad substrate scope, and good functional‐group tolerance. Based on DFT calculations, a radical adds to an unactivated alkene to smoothly form a new carbon radical, followed by a 1,5‐hydrogen atom‐transfer process, the rate‐limiting step, generating a more stable benzylic radical. The reduction of the benzylic radicals by an IrII species generates the corresponding benzylic carbanions as the key intermediates, which further undergo nucleophilic attack with CO2 to generate carboxylates. [ABSTRACT FROM AUTHOR]

Vinylcyclopropanes (VCPs) are commonly used in transition‐metal‐catalyzed cycloadditions, and the utilization of their recently realized reactivities to construct new cyclic architectures is of great significance in modern synthetic chemistry. Herein, a palladium‐catalyzed, visible‐light‐driven, asymmetric [5+2] cycloaddition of VCPs with α‐diazoketones is accomplished by switching the reactivity of the Pd‐containing dipolar intermediate from an all‐carbon 1,3‐dipole to an oxo‐1,5‐dipole. Enantioenriched seven‐membered lactones were produced with good reaction efficiencies and selectivities (23 examples, 52–92 % yields with up to 99:1 er and 12.5:1 dr). In addition, computational investigations were performed to rationalize the observed high chemo‐ and periselectivities. [ABSTRACT FROM AUTHOR]

Higher‐order cycloadditions, particularly [8+2] cycloadditions, are a straightforward and efficient strategy for constructing significant medium‐sized architectures. Typically, configuration‐restrained conjugated systems are utilized as 8π‐components for higher‐order concerted cycloadditions. However, for this reason, 10‐membered monocyclic skeletons have never been constructed via catalytic asymmetric [8+2] cycloaddition with high peri‐ and stereoselectivity. Here, we accomplished an enantioselective [8+2] dipolar cycloaddition via the merger of visible‐light activation and asymmetric palladium catalysis. This protocol provides a new route to 10‐membered monocyclic architectures bearing chiral quaternary stereocenters with high chemo‐, peri‐, and enantioselectivity. The success of this strategy relied on the facile in situ generation of Pd‐containing 1,8‐dipoles and their enantioselective trapping by ketene dipolarophiles, which were formed in situ via a photo‐Wolff rearrangement. [ABSTRACT FROM AUTHOR]

Remote difunctionalization of unactivated alkenes is challenging but a highly attractive tactic to install two functional groups across long distances. Reported herein is the first remote difunctionalization of alkenes with CO2. This visible‐light photoredox catalysis strategy provides a facile method to synthesize a series of carboxylic acids bearing valuable fluorine‐ or phosphorus‐containing functional groups. Moreover, this versatile protocol shows mild reaction conditions, broad substrate scope, and good functional‐group tolerance. Based on DFT calculations, a radical adds to an unactivated alkene to smoothly form a new carbon radical, followed by a 1,5‐hydrogen atom‐transfer process, the rate‐limiting step, generating a more stable benzylic radical. The reduction of the benzylic radicals by an IrII species generates the corresponding benzylic carbanions as the key intermediates, which further undergo nucleophilic attack with CO2 to generate carboxylates. [ABSTRACT FROM AUTHOR]

Axial‐to‐central chirality transfer is an important strategy to construct chiral centers, where the axially chiral reagents are mostly limited to atropomerically stable ones. Reported herein is a RhIII‐catalyzed enantioselective spiroannulative synthesis of nitrones. The coupling proceeds via C−H arylation to give an atropomerically metastable biaryl, followed by intramolecular dearomative trapping under oxidative conditions with high degree of chirality transfer. [ABSTRACT FROM AUTHOR]

An unprecedented stereoselective synthesis of trisubstituted vinylboronates is reported to proceed by direct borylation of lithium ketone enolates under transition‐metal‐free conditions. The stereospecific C−O borylation of lithium enolates was triggered by a carbonyl‐induced 1,3‐metalate rearrangement via a C‐bound boron enolate. DFT calculations and control experiments revealed that the stereoselectivity is controlled by sterics. A variety of stereospecific trisubstituted vinylboronates, together with several tetrasubstituted vinylboronates, were conveniently synthesized with the newly developed methodology. Based on the transformation of stereospecific vinylboronate, a single isomer of Dienestrol was efficiently obtained. [ABSTRACT FROM AUTHOR]

Catalytic asymmetric cycloadditions of ambident Pd‐containing dipolar species with nucleophilic dipolarophiles, namely, inverse‐electron‐demand cycloadditions, are challenging and underdeveloped. Possibly, the inherent linear selectivity of Pd‐catalyzed intermolecular allylations and the lack of efficient chiral ligands are responsible for this limitation. Herein, two cycloadditions of such intermediates with deconjugated butenolides and azlactones were accomplished by using a novel chiral hybrid P,S‐ligand and hydrogen bonding. By doing so, highly functionalized, optically active dihydroquinol‐2‐ones were produced with generally high reaction efficiencies and selectivities. Preliminary DFT calculations were performed to explain the high enantio‐ and diastereoselectivities. [ABSTRACT FROM AUTHOR]

The synthesis, characterization, and C(sp2)−CF3 reductive elimination of stable aryl[tris(trifluoromethyl)]cuprate(III) complexes [nBu4N][Cu(Ar)(CF3)3] are described. Mechanistic investigations, including kinetic studies, studies of the effect of temperature, solvent, and the para substituent of the aryl group, as well as DFT calculations, suggest that the C(sp2)−CF3 reductive elimination proceeds through a concerted carbon–carbon bond‐forming pathway. [ABSTRACT FROM AUTHOR]

The discovery of proper ligands to simultaneously modulate the reactivity and effectively control the stereoselectivity is a central topic in the field of enantioselective C−H activation. Herein, we reported the synthesis of axially chiral biaryls by Pd‐catalyzed atroposelective C−H olefination. A novel chiral spiro phosphoric acid, STRIP, was identified as a superior ligand for this transformation. A broad range of axially chiral quinoline derivatives were synthesized in good yields with excellent enantioselectivities (up to 98 % ee). Density functional theory was used to gain a theoretical understanding of the enantioselectivities in this reaction. [ABSTRACT FROM AUTHOR]

Abstract: A highly para‐selective CAr−H difluoromethylation of ketoxime ethers under ruthenium catalysis has been developed. A wide variety of ketoxime ethers are compatible with the reaction, which leads to the corresponding para‐difluoromethylated products in moderate to good yield. A mechanistic study clearly showed that chelation‐assisted cycloruthenation is the key factor in the para selectivity of the difluoromethylation of ketoxime ethers. Density functional theory was used to gain a theoretical understanding of the para selectivity.# [ABSTRACT FROM AUTHOR]

Homodimericin A is a remarkable fungal metabolite. This highly oxygenated racemic unsaturated polyketide poses a significant synthetic challenge owing to its sterically demanding central cagelike core containing eight contiguous stereogenic centers (including three quaternary stereocenters) and several carbonyl functionalities. On the basis of its proposed biogenetic synthesis, we designed a total synthesis of homodimericin A that proceeds in seven steps and features a double Michael reaction, an intramolecular Diels-Alder reaction, and an ene reaction. [ABSTRACT FROM AUTHOR]

The first enantiospecific synthesis of hispidanin A ( 4), a dimeric diterpenoid from the rhizomes of Isodon hispida, was achieved with a longest linear sequence of 12 steps in 6.5 % overall yield. A key component is the use of the abundant and naturally occurring diterpenoids (+)-sclareolide and (+)-sclareol as starting materials, which enables the gram-scale preparation of the key intermediates totarane ( 1) and s- trans-12E,14-labdadien-20,8β-olide ( 2). Subsequently a thermal or an erbium-catalyzed intermolecular Diels-Alder reaction of totarane ( 1) with labdadienolide ( 2) provide convergent and rapid access to the natural product hispidanin A ( 4). The synthetic studies have offered significant impetus for the efficient construction of these architecturally complex natural products. [ABSTRACT FROM AUTHOR]

The enantioselective α-addition of deconjugated butenolides has rarely been exploited, in contrast to the well-studied γ-addition of deconjugated butenolides. In this study, an unprecedented asymmetric α-addition/transesterification of deconjugated butenolides with ortho-quinone methides generated in situ afforded a series of functionalized 3,4-dihydrocoumarins containing two contiguous stereogenic centers with excellent diastereo- and enantioselectivity. DFT calculations suggested that the rarely observed regioselectivity was due to the distortion energy that resulted from the interaction between the nucleophilic dienolate and the electrophilic ortho-quinone methide. [ABSTRACT FROM AUTHOR]

The influence of the alcohol, as the hydrogen donor, on the efficiency and selectivity of the asymmetric transfer hydrogenation (ATH) of imines is reported for the first time. This discovery not only leads to a highly enantioselective access to N-aryl and N-alkyl amines, but also provides new insight into the mechanism of the ATH of imines. Both experimental and computational studies provide support for the reaction pathway involving an iridium alkoxide as the reducing species. [ABSTRACT FROM AUTHOR]

Previous direct C−H nitrogenation suffered from simple amidation/amination with limited atom-economy and is mostly limited to C(sp2)−H substrates. In this work, anthranil was designed as a novel bifunctional aminating reagent for both C(sp2)−H and C(sp3)−H bonds under rhodium(III) catalysis, thus affording a nucleophilic aniline tethered to an electrophilic carbonyl. A tridendate rhodium(III) complex has been isolated as the resting state of the catalyst, and DFT studies established the intermediacy of a nitrene species. [ABSTRACT FROM AUTHOR]

The first example of iron-catalyzed decarboxylative (4+1) cycloaddition reactions is described in this publication. By using this method, a wide range of functionalized indoline products were prepared from easily available vinyl benzoxazinanones and sulfur ylides in high yields and selectivities. A possible reaction pathway involving an allylic iron intermediate is discussed based on a series of control experiments and density-functional theory calculations. [ABSTRACT FROM AUTHOR]

A transition-metal-free formal decarboxylative coupling reaction between α-oxocarboxylates and α-bromoketones to synthesize 1,3-diketone derivatives is presented. In this reaction, a broad scope of substrates can be employed, and neither a metal-based reagent nor an additional base is required. DFT calculations reveal that this reaction proceeds through a coupling followed by decarboxylation mechanism and the α-bromoketone unprecedentedly serves as a nucleophile under neutral conditions. The rate-determining step is an unusual hydrogen-bond-assisted enolate formation by thermolysis. [ABSTRACT FROM AUTHOR]

The chemoselective addition of arenes and 1,3-diketones to α-aryldiazoesters was achieved through ligand-controlled gold catalysis. Unlike a dirhodium catalyst (which promotes C [ABSTRACT FROM AUTHOR]

The stannum–ene reactions of both benzyne and cyclohexyne were realized, which is particularly suitable for cyclohexyne with a broad substrate scope and excellent chemoselectivity. Our DFT calculations via distortion/interaction analysis revealed that both stannum– and hydrogen–ene reactions with cyclohexyne have later transition states due to their higher distortion energies in the transition states than those in benzyne reactions, which lead to enhanced Pauli repulsion as the decisive factor in the interaction energy accompanied with enlarged energy gap between two types of ene reactions. Therefore, excellent chemoselectivity was disclosed in the cyclohexyne–ene reaction. [ABSTRACT FROM AUTHOR]