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We report the ruthenium-catalyzed cyclization of 1,6-diynes with two molecules of carbon monoxide and water to give a variety of catechols. This reaction likely proceeds through the intermediacy of...

The synthesis of indanone derivatives by the Rh(III)-catalyzed reaction of α-carbonyl sulfoxonium ylides with activated alkenes is reported. The reaction shows a high tolerance for functional groups and furnishes a variety of substituted indanone derivatives via a formal [4 + 1] cycloaddition. Highly stable sulfoxonium ylides were used as substrates in this C-H functionalization, and their bifunctional character could be effectively exploited using Rh(III) catalysis via sequential double C-C bond formation. Based on mechanistic studies including deuterium-labeling experiments, the reaction is proposed to proceed as follows: Rh(III)-catalyzed C-H oxidative alkenylation via β-hydride elimination, readdition of H-Rh species, a 1,2-carbon shift with the elimination of DMSO, and protonation.

The metal-free

The nickel-catalyzed reaction of aromatic amides that contain an 8-aminoquinoline as a directing group with bicyclic alkenes, such as norbornene and 1,4-dihydro-1,4-epoxynaphthalene, results in the cleavage of both the C-H bond at the ortho-position of the benzene ring and the C(O)-N bond to give methanofluoren-9-one and 1,4-epoxyfluoren-9-one derivatives. Both Ni(OTf)

Redox isomerization reaction wherein N-alkylpropargylamines are converted into N-alkylideneallylamines in the presence of rhenium(I) complexes as catalysts is described. Among the additives tested, certain pyridine N-oxides and tertiary amine N-oxides were effective for the reaction to proceed, and in particular, the use of 2,6-lutidine N-oxides gave the best results. The choice of a diphenylmethyl group as a substituent on the nitrogen atom was key to the success of the reaction, allowing it to reach completion.

The Rh-catalyzed C-H alkylation of benzylamine derivatives with unactivated 1-alkenes that proceeds via a picolinamide directing group is reported. The crucial role of an acid additive in this transformation is confirmed. Aromatic acids showed high linear selectivity, and aliphatic acids provided branched alkylation products as the major product. The reaction has a broad scope for benzylamines and alkenes. Deuterium labeling experiments suggest that a Rh-carbene intermediate is involved in the case of linear product formation. A different reaction pathway, however, appears to be involved in the case of branched alkylation products, and this pathway also appeared to be a minor pathway in linear-selective reactions.

The regioselective Rh(III)-catalyzed C-H amidation of aniline derivatives with dioxazolones as an amidating reagent with a pyrimidine as a directing group leading to the production of 1,2-diaminobenzene derivatives or benzimidazole derivatives is described. The product distribution is controlled by the nature of solvent used. The reaction provides a broad substrate scope for aniline derivatives with various important functional groups including dioxazolones.

The rhodium-catalyzed alkynylation of aryl carbamates with propargyl alcohols is described. This methodology can provide aryl acetylenes from aryl carbamates via C-O bond activation. The use of propargyl alcohols as alkynylating agents allows the use of a variety of functional groups that are incompatible with organometallic nucleophiles. This reaction also serves to broaden the utility of a carbamate moiety as a convertible ortho directing group.

The cobalt(II)-catalyzed acyloxylation of C-H bonds in aromatic amides containing an 8-aminoquinoline moiety as the directing group with carboxylic acids is reported. Various carboxylic acids including aromatic and aliphatic carboxylic acids are applicable to the reaction. The reaction displays a broad substrate scope and high functional group tolerance. The reaction is carried out under air.

An alkylation of C-H bonds with maleimides by a rhodium-catalyzed reaction of aromatic amides containing an 8-aminoquinoline moiety as the directing group is reported. Various N-substituents in the maleimide, including methyl, ethyl, cyclohexyl, benzyl, and phenyl groups and even H, are applicable to the reaction. The reaction is highly regioselective at the less hindered ortho-C-H bond when meta-substituted aromatic amides are used as substrates.

The cobalt-catalyzed chelation-assisted C-H iodination of aromatic amides using molecular iodine as an iodinating reagent is reported. The reaction is carried out in an atmosphere of air and uses Co(OAc)

A new method has been developed for the synthesis of 2,3-disubstituted benzothiophenes involving the palladium-catalyzed annulation of aryl sulfides with alkynes. This convergent approach exhibited good functional group tolerance, providing rapid access to a diverse array of derivatives from simple, readily available starting materials. This protocol can also be used to synthesize 2-silyl-substituted benzothiophenes, which can be used as versatile platforms for the synthesis of 2,3-unsymmetrically substituted benzothiophenes.

A new method has been developed for the nickel-catalyzed homocoupling of methoxyarenes via C-O bond cleavage using a diboron reagent. The use of 1,3-dicyclohexylimidazol-2-ylidene as a ligand was found to be critical to the success of the reaction. This new method allows the synthesis of a wide range of biaryl compounds.

A new cross-coupling reaction has been developed for the introduction of an alkyne moiety to an anisole derivative through C-O bond activation using an NHC ligand. This method has been used for direct alkynylation of a broad range of anisole derivatives and provided rapid access to compounds with potential applications in biological and materials science.

The rhodium-catalyzed alkenylation of C–H bonds of aromatic amides with alkynes is reported. A variety of functional groups, including OMe, OAc, Br, Cl, and even NO2, are applicable to this reaction to give the corresponding hydroarylation products. The presence of an 8-aminoquinoline group as the directing group is crucial for the success of the reaction.

The direct methylation of ortho C–H bonds in aromatic amides with dicumyl peroxide (DCP) using a nickel complex as the catalyst is reported. The reaction shows a high functional group tolerance and is inhibited by radical scavengers. In reactions of meta-substituted aromatic amides, the reaction proceeds in a highly selective manner at the less hindered C–H bonds.

The palladium-catalyzed direct alkynylation of C-H bonds in aromatic carboxylic acid derivatives is described. The use of 8-aminoquinoline as a directing group facilitates the alkynylation of an electronically diverse range of C(sp(2))-H bonds.

Nickel-catalyzed cross-coupling of methoxyarenes with alkyl Grignard reagents, which involves the cleavage of the C(aryl)–OMe bond, has been developed. The use of 1,3-dicyclohexylimidazol-2-ylidene as a ligand allows the introduction of a variety of alkyl groups, including Me, Me3SiCH2, ArCH2, adamantyl, and cyclopropyl. The method can also be used for the alkylative elaboration of complex molecules bearing a C(aryl)–OMe bond.

Rhodium-catalyzed alkylation reactions of aromatic C–H bonds in aromatic amides with styrene derivatives have been developed by using an 8-aminoquinoline as a bidentate directing group. C–C bond formation selectively occurred between the ortho C–H bonds in aromatic amides and the terminal carbon of the styrene derivatives. The presence of an 8-aminoquinoline moiety is essential for the success of the reaction.

The palladium-catalyzed synthesis of dibenzofused six-membered phosphacycles via carbon-phosphorus bond cleavage is developed. This method is compatible with a range of functional groups, such as esters, amides, and carbamates, which is in sharp contrast to the limitations of the classical method using organolithium reagents.

The Ni(0)-catalyzed cross-coupling of alkenyl methyl ethers with boronic esters is described. Several types of alkenyl methyl ethers can be coupled with a wide range of boronic esters to give the stilbene derivatives.

Palladium-catalyzed ortho-alkynylation of aromatic C-H bonds in anilides is described. Preliminary mechanistic studies reveal that electrophilic palladation is involved. Synthetic elaborations of alkynylated products are also demonstrated.

The reaction of yne esters with carbon monoxide (1 atm) in the presence of palladium complexes gives bicyclic unsaturated lactone derivatives in good to high yields. The 2-pyridinyloxy group is a g...

The rhodium-catalyzed reaction of 2-germylphenylboronic esters with alkynes in the presence of a rhodium(I) catalyst is established as a modular method for the synthesis of an array of benzogermole derivatives. The reaction proceeds through the activation of C(sp(3))-Ge bonds. The mechanism of this new bond activation process is discussed based on the activation aptitude of alkyl and aryl substituents on germanium.

Ni-catalyzed hydrosilylative cyclization of difluoro-substituted 1,6-enynes can be carried out. The presence of a geminal-difluoromethylene group at an alkene terminus in enynes is essential for the reaction to proceed.

Rhodium-catalyzed Mizoroki−Heck type reaction of nitriles via the cleavage of C−C bonds is described. Orthogonal and iterative functionalizations of arenes were also demonstrated by combining the present and conventional halide-based cross-coupling reactions.

The rhodium(I)-catalyzed reaction of alkynes with 2-bromophenylboronic acids in the presence of paraformaldehyde resulted in a CO gas-free carbonylative cyclization, yielding indenone derivatives. [RhCl(BINAP)](2) and [RhCl(cod)](2) were responsible for the decarbonylation of formaldehyde and the subsequent carbonylation of alkynes with 2-haloboronic acids, respectively, leading to efficient whole carbonylation. Sterically bulky and electron-withdrawing groups on unsymmetrically substituted alkynes favored the alpha-position of indenones.

Ruthenium-catalyzed alkenylation of 2′-alkoxyacetophenones with alkenylboronates provides ortho C−H alkenylation products without sacrificing an ether functional group at the other ortho position. Both excellent chemoselectivity and high product yields are achieved with an aryloxo ruthenium complex. The effective suppression of the C−O bond cleavage was attained by coordination of the alkenyl moiety in the C−H alkenylation product to the ruthenium center.

The insertion reaction of isocyanide into a C-S bond of dithioacetals is catalyzed by GaCl3 or TiCl4 to afford thioimidates containing an alpha-alkylthio group. Balanced thiophilicity of these Lewis acids is critical for efficient catalysis.

The reaction of 2-(chloromethyl)phenylboronic acid (1) with alkynes in the presence of a Rh(I) complex gave indene derivatives in high yields. The regioselectivity depends on the steric nature of the substituent on the alkynes. A bulky group favors the alpha-position of indenes.

The Lewis acid-promoted insertion of isocyanides into aromatic C−H bonds is reported. An imine functionality containing an array of N-substituents can be introduced directly into electron-rich aromatics in good yields.

The reaction of internal alkynes 1 with CO and pyridin-2-ylmethanol (2) in the presence of Rh(4)(CO)(12) results in a double-hydroesterification leading to 1,4-dicarboxylate esters 3. The reaction does not proceed via two consecutive hydroesterifications of alkynes, but the intermediacy of ketene intermediates is proposed. The coordination of the pyridine nitrogen in 2 to rhodium is essential for the reaction to proceed. [reaction: see text]

[reaction: see text] The skeletal reorganization of enynes is achieved by the presence of InCl(3) as the catalyst. The reaction of enynes having a terminal acetylenic moiety proceeds in a stereospecific manner to give 1-vinylcycloalkenes. The reaction of enynes containing an alkyl group on the acetylenic terminal carbon resulted in a new type of skeletal reorganization to give 1-allylcycloalkenes, formation of which involves a double cleavage of the C-C double bond and the triple bond.

[reaction: see text] The reaction of yne esters with carbon monoxide (1 atm) in the presence of palladium complexes gives bicyclic unsaturated lactone derivatives in good to high yields. The 2-pyridinyloxy group is a good leaving group among leaving groups examined.

The reaction of cyclic ketals or acetals with 2,6-dibromophenylisocyanide in the presence of a catalytic amount of GaCl(3) results in the insertion of isocyanide into the carbon-oxygen bond of cyclic ketals and acetals. [reaction: see text]

[Reaction: see text] GaCl3 is found to be a superior catalyst for the skeletal rearrangement of alpha,alpha,alpha-trisubstituted aldehydes to ketones. The rearrangement can proceed smoothly in the presence of a catalytic amount of GaCl3, and even substrates having no heteroatoms alpha to the carbonyl group or without steric strains can be used. Double activation of a carbonyl group by two molecules of GaCl3 was supported on the basis of experimental data and a DFT study.

The reaction of adamantane (1) with CO (1 atm) in 1,2-dichloroethane at room temperature in the presence of GaCl(3) results in formylation to give 1-adamantanecarboxaldehyde (2) in up to 84% yield.