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A binary hybrid system comprising a hypervalent iodine(III) reagent and BF 3 •OEt 2 Lewis acid was found to be effective for the diastereoselective α-acetoxylation of cyclic ketones. In this hybrid system, BF 3 •OEt 2 Lewis acid allowed the activation of the hypervalent iodine(III) reagent and cyclic ketones for smooth α-acetoxylation reaction, achieving high diastereoselectivity. This hypervalent iodine-mediated α-acetoxylation of the cyclic ketone reaction plausibly undergoes an S N 2 substitution mechanism via an α- C -bound hypervalent iodine intermediate. The diastereoselectivity of the reaction mainly originates from thermodynamic control., (Copyright © 2020 Tan, Zhu, Xu, Jing, Ke, Liu and Maruoka.)

The mono-base-stabilized 1,2-diboranylidenehydrazine derivatives featuring a 1,3-dipolar BNN skeleton are obtained by dehydrobromination of [ArB(Br)NH] 2 (Ar = 2,6-diphenylphenyl (Dpp), Ar = 2,6-bis(2,4,6-trimethylphenyl)phenyl (Dmp) or Ar = 2,4,6-tri- tert -butylphenyl (Mes*)) with N-heterocyclic carbenes (NHCs). Depending on the Ar substituents, such species can be isolated as a crystalline solid (Ar = Mes*) or generated as reactive intermediates undergoing spontaneous intramolecular aminoboration of the proximal arene rings via [3 + 2] cycloaddition (Ar = Dpp or Dmp). The latter reactions showcase the 1,3-dipolar reactivity toward unactivated arenes at ambient temperature. In addition, double cycloaddition of the isolable BNN species with two CO 2 molecules affords a bicyclic species consisting of two fused five-membered BN 2 CO rings. The electronic structures of these BNN species and the mechanisms of these cascade reactions are interrogated through density functional theory (DFT) calculations., Competing Interests: The authors declare no competing financial interests., (This journal is © The Royal Society of Chemistry.)

A sustainable and green route to access diverse functionalized ketones via dehydrogenative-dehydrative cross-coupling of primary and secondary alcohols is demonstrated. This borrowing hydrogen approach employing a pincer N-heterocyclic carbene Mn complex displays high activity and selectivity. A variety of primary and secondary alcohols are well tolerant and result in satisfactory isolated yields. Mechanistic studies suggest that this reaction proceeds via a direct outer-sphere mechanism and the dehydrogenation of the secondary alcohol substrates plays a vital role in the rate-limiting step., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Five molecular complexes with different non-noble metal centers were synthesized. The Co-based complex displays the highest photocatalytic performance for CO 2 to CO conversion in aqueous media. It achieves high activity (TON = 41 017 and TOF = 3.80 s -1 ) and selectivity (87%) for the production of CO.

A theoretical approach was used to investigate the hydrolytic cleavage mechanisms of the bis( p -nitrophenyl) phosphate (BNPP - ) catalyzed by Zn(ii)-complexes featuring uncoordinated nucleophiles. Ligand-based and alternative solvent-based nucleophilic attack reaction models are proposed. The p K a values of the Zn(ii)-bound water molecules or ligands in the [Zn(L n H)(η-H 2 O)(H 2 O)] 2+ ( n = 1, 2 and 3) complexes, as well as the dimerization tendency of the mononuclear Zn(ii)-complexes, were found to significantly influence the reaction mechanisms. The Zn(ii)-L 3 complexes were found to be more favorable for the hydrolytic cleavage of the BNPP - via a ligand-based nucleophilic attack pathway. This was due to the lower p K a value for the deprotonation of the oxime ligand, the hard dimerization of the mononuclear Zn(ii)-L 3 species, and the presence of an uncoordinated nucleophile. The origins of the uncoordinated reactions were systematically elucidated. The theoretical results reported here are in good agreement with experimental observations and more importantly, help to elucidate the factors that influence intermolecular nucleophilic attack reactions with coordinated/uncoordinated nucleophiles., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The creation of supramolecular assemblies by assembly of structurally simple components via supramolecular interactions provides an opportunity to develop functional materials with hierarchical complexibility. Herein, we report an assembly approach to supramolecular gels based on metal-organic cages with tunable hierarchical structures and properties. A Pd 12 L 24 cage ( L is cholesteryl-functionalized 3,5-bis(4-pyridyl)benzene) bearing 24 cholesteryl groups is used as a supramolecular building unit and molecular platform for functionalization with tunable functional behaviors. The Pd 12 L 24 cage motifs spontaneously self-assemble into gels where orthogonal metal-organic coordination and cholesteryl-cholesteryl interactions are involved in the gelation. The Pd 12 L 24 cage exhibits a reversible transition between solution and aggregated gel states in response to temperature. The gelation and the mechanical property are rarely regulated by deuterated solvents and tetramethylsilane. The mechanical property of the gel materials is tunable by varying the content of cholesteryl groups of Pd 12 L 24 . Functional moieties (e.g., luminescent TPE group) can be introduced on the cage, and the luminescent property changes while the structure is maintained. The Pd 12 L 24 gel shows visible anion-responsive behaviors arising from the hierarchical structure.

Optically active organoboronic acids and their derivatives are an important family of target compounds in organic chemistry, catalysis, and medicinal chemistry. Yet there are rare asymmetric catalytic examples reported for the synthesis of these compounds via atom and step economic ways. Herein, we report a chelate-directed iridium-catalyzed asymmetric C(sp 2 )-H borylation of aromatic C-H bonds directed by free amine groups. The success of these transformations relies on a novel family of chiral bidentate boryl ligands (L). They can be synthesized straightforwardly in three steps starting from readily available ( S, S)-1,2-diphenyl-1,2-ethanediamie (( S, S)-DPEN). The Ir-catalyzed C(sp 2 )-H borylation comprises two parts. The first part is desymmetrization of prochiral diarylmethylamines. In the presence of L3/Ir, a vast array of corresponding borylated products were obtained with high regioselectivity and good to excellent enantioselectivities (26 examples, up to 96% ee). The second part, kinetic resolution of racemic diarylmethylamines, was also conducted. Good selectivity values (up to 68%, 11 examples) were obtained when L8 was used. We also demonstrated the synthetic utility of the current method on gram-scale reaction for several transformations. The C-B bonds of borylated products could be converted to a variety of functionalities including C-O, C-C, C-C, C-Br, and C-P bonds. Finally, we performed DFT calculations of desymmetrization to understand its reaction pathways.

Incorporation of nitrile groups into fine chemicals is of particular interest through C(sp 3 )-H bonds activation of alkyl nitriles in the synthetic chemistry due to the highly efficient atom economy. However, the direct α-functionalization of alkyl nitriles is usually limited to its enolate chemistry. Here we report an electro-oxidative C(sp 3 )-H bond functionalization of acetonitrile with aromatic/aliphatic mercaptans for the synthesis of sulfur-containing β-enaminonitrile derivatives. These tetrasubstituted olefin products are stereoselectively synthesized and the stereoselectivity is enhanced in the presence of a phosphine oxide catalyst. With iodide as a redox catalyst, activation of C(sp 3 )-H bond to produce cyanomethyl radicals proceeds smoothly at a decreased anodic potential, and thus highly chemoselective formation of C-S bonds and enamines is achieved. Importantly, the process is carried out at ambient temperature and can be easily scaled up.

A Rh(iii)-catalyzed regioselective intermolecular carbenoid insertion into the N -methylene Csp 3 -H bond of acyclic aliphatic amides has been achieved, taking advantage of bidentate-chelation assistance. This methodology has been successfully applied to a broad range of linear and branched-chain N -alkylamides, thus providing a practical method for the assembly of diverse beta-amino esters. Mechanism studies and density functional theory (DFT) calculations revealed that a singlet Fischer type carbene insertion via an outer-sphere pathway was involved in this N -methylene Csp 3 -H bond carbenoid insertion.

For the first time, a highly regioselective intermolecular sulfonylamidation unactivated secondary Csp(3) -H bond has been achieved using Ir(III) catalysts. The introduced N,N'-bichelating ligand plays a crucial role in enabling iridium-nitrene insertion into a secondary Csp(3) -H bond via an outer-sphere pathway. Mechanistic studies and density functional theory (DFT) calculations demonstrated that a two-electron concerted nitrene insertion was involved in this Csp(3) -H amidation process. This method tolerates a broad range of linear and branched-chain N-alkylamides, and provides efficient access to diverse γ-sulfonamido-substituted aliphatic amines., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The potential-energy surfaces of the reactions of dirhodium tetracarboxylate (Rh2(II,II)) catalyzed nitrene (NR) insertion into C-H bonds were examined by a DFT computational study. A pure Becke exchange functional (B88) rather than a hybrid exchange functional (B3, BHandH) was found to be appropriate for the calculation of the energy difference between the singlet and triplet Rh2(II,II)-NH nitrene species. Rh2(II,II)-NR1 (R1 = (S)-2-methyl-1-butylformyl) is thermodynamically more favorable with a free energy lower than that of Rh2(II,II)-N(PhI)R1. The singlet and triplet states of Rh2(II,II)-NR1 have similar stability. Singlet Rh2(II,II)-NR1 undergoes a concerted NR insertion into the C-H bond with simultaneous formation of the N-H and N-C bonds during C-H bond cleavage; triplet Rh2(II,II)-NR1 undergoes H atom abstraction to produce a diradical, followed by subsequent bond formation by diradical recombination. The singlet pathway is favored over the triplet in the context of the free energy of activation and leads to the retention of the chirality of the C atom in the NR insertion product. The reactivities of the C-H bonds toward the nitrene-insertion reaction follow the order tertiary > secondary > primary. Relative reaction rates were calculated for the six reaction pathways examined in this work.

An investigation into the mechanism and stereochemistry of chiral lithium-carbenoid-promoted cyclopropanation reactions by using density functional theory (DFT) methods is reported. Previous work suggested that this type of cyclopropanation reaction may proceed by competition between a methylene-transfer mechanism and a carbometalation mechanism. In this paper, it is demonstrated that the intramolecular cyclopropanation reactions promoted by chiral carbenoids 1 and 2 proceed by the methylene-transfer mechanism. The carbometalation mechanism was found to have a much higher reaction barrier and does not appear to compete with the methylene-transfer mechanism. The Lewis base group does not enhance the carbometalation pathway enough to compete with the methylene-transfer pathway. The present computational results are consistent with experimental observations for these cyclopropanation reactions. The factors governing the stereochemistry of the intramolecular cyclopropanation reaction by the methylene-transfer mechanism were examined to help elucidate the origin of the stereoselectivity observed in experiments. Both the directing group and the configuration at the C(1) centre were found to play a key role in the stereochemistry. Carbenoid 1 has a chiral C(1) centre of R configuration. The Lewis base group directs the cyclization of carbenoid 1 to form a single product. In contrast, the Lewis base group cannot direct the cyclization of carbenoid 2 to furnish a stereoselective product due to the S configuration of the chiral C(1) centre in carbenoid 2. This relationship of the stereochemistry to the chiral character of the carbenoid has implications for the design of new efficient carbenoid reagents for stereoselective cyclopropanation.