Rhodium(III)-catalyzed intermolecular amidation with azides via C(sp³)-H functionalization.

The amidation reactions of 8-methylquinolines with azides catalyzed by a cationic rhodium(III) complex proceed efficiently to give quinolin-8-ylmethanamine derivatives in good yields via C(sp(3))-H bond activation under external oxidant-free conditions. A catalytically competent five-membered rhodacycle has been isolated and characterized, revealing a key intermediate in the catalytic cycle.

Rhodium(III)-catalyzed alkenylation reactions of 8-methylquinolines with alkynes by C(sp3)-H activation.

The alkenylation reactions of 8-methylquinolines with alkynes, catalyzed by [{Cp*RhCl2}2], proceeds efficiently to give 8-allylquinolines in good yields by C(sp(3))-H bond activation. These reactions are highly regio- and stereoselective. A catalytically competent five-membered rhodacycle has been structurally characterized, thus revealing a key intermediate in the catalytic cycle.

Regioselective C2 Oxidative Olefination of Indoles and Pyrroles through Cationic Rhodium(III)-Catalyzed C-H Bond Activation.

Be economic with your atoms! An efficient Rh-catalyzed oxidative olefination of indoles and pyrroles with broad substrate scope and tolerance is reported. The catalytic reaction proceeds with excellent regio- and stereoselectivity. The directing group N,N-dimethylcarbamoyl was crucial for the reaction and could be removed easily.

Investigation and comparison of the mechanistic steps in the [(Cp*MCl2)2] (Cp* = C5Me5; M = Rh, Ir)-catalyzed oxidative annulation of isoquinolones with alkynes.

The mechanism of the [(Cp*MCl(2))(2)] (M = Rh, Ir)-catalyzed oxidative annulation reaction of isoquinolones with alkynes was investigated in detail. In the first acetate-assisted C-H-activation process (cyclometalated step) and the subsequent mono-alkyne insertion into the M-C bonds of the cyclometalated compounds, both Rh and Ir complexes participated well. However, the desired final products, dibenzo[a,g]quinolizin-8-one derivatives, were only formed in high yield when the Rh species participated in the final oxidative coupling of the C-N bond. Moreover, a Rh(I) sandwich intermediate was isolated during this transformation. The iridium complexes were found to be inactive in the oxidative coupling processes. All of the relevant intermediates were fully characterized and determined by single-crystal X-ray diffraction analysis. Based on this mechanistic study, a Rh(III)→Rh(I)→Rh(III) catalytic cycle was proposed for this reaction.

Ruthenium-catalyzed regioselective C2 alkenylation of indoles and pyrroles via C-H bond functionalization.

An efficient ruthenium-catalyzed oxidative coupling of indoles and pyrroles with various alkenes at the C2-position assisted by employing the N,N-dimethylcarbamoyl moiety as a directing group is reported. The catalytic reaction proceeds in an excellent regio- and stereoselective manner.

Rhodium-catalyzed cascade oxidative annulation leading to substituted naphtho[1,8-bc]pyrans by sequential cleavage of C(sp2)-H/C(sp3)-H and C(sp2)-H/O-H bonds.

The cascade oxidative annulation reactions of benzoylacetonitrile with internal alkynes proceed efficiently in the presence of a rhodium catalyst and a copper oxidant to give substituted naphtho[1,8-bc]pyrans by sequential cleavage of C(sp(2))-H/C(sp(3))-H and C(sp(2))-H/O-H bonds. These cascade reactions are highly regioselective with unsymmetrical alkynes. Experiments reveal that the first-step reaction proceeds by sequential cleavage of C(sp(2))-H/C(sp(3))-H bonds and annulation with alkynes, leading to 1-naphthols as the intermediate products. Subsequently, 1-naphthols react with alkynes by cleavage of C(sp(2))-H/O-H bonds, affording the 1:2 coupling products. Moreover, some of the naphtho[1,8-bc]pyran products exhibit intense fluorescence in the solid state.

Ruthenium-catalyzed oxidative coupling/cyclization of isoquinolones with alkynes through C-H/N-H activation: mechanism study and synthesis of dibenzo[a,g]quinolizin-8-one derivatives.

The mechanism of [{RuCl(2)(p-cymene)}(2)]-catalyzed oxidative annulations of isoquinolones with alkynes was investigated in detail. The first step is an acetate-assisted C-H bond activation process to form cyclometalated compounds. Subsequent mono-alkyne insertion of the Ru-C bonds of the cyclometalated compounds then takes place. Finally, oxidative coupling of the C-N bond of the insertion compounds occurs to afford Ru(0) sandwich complexes that undergo oxidation to regenerate the catalytically active Ru(II) complex with the copper oxidant and release the desired dibenzo[a,g]quinolizin-8-one derivatives. All of the relevant intermediates were fully characterized and determined by single crystal X-ray diffraction analysis. The [{RuCl(2)(p-cymene)}(2)]-catalyzed C-H bond functionalization of isoquinolones with alkynes to synthesize dibenzo[a,g]quinolizin-8-one derivatives through C-H/N-H activation was also demonstrated.

Rh(III)-catalyzed synthesis of 1-aminoindole derivatives from 2-acetyl-1-arylhydrazines and diazo compounds in water.

A novel and direct approach to synthesize 1-aminoindole derivatives by Rh(iii)-catalyzed cyclization of 2-acetyl-1-arylhydrazines with diazo compounds via aryl C-H activation has been developed. This intermolecular annulation involving tandem C-H activation, cyclization and condensation steps proceeds efficiently in water, obviates the need of external oxidants, and displays a broad substituent scope.

Ruthenium-catalyzed pyrrole synthesis via oxidative annulation of enamides and alkynes.

An efficient and regioselective ruthenium-catalyzed oxidative annulation of enamides with alkynes via the cleavage of C(sp(2))-H/N-H bonds is reported. The reactions can afford N-acetyl substituted or N-unsubstituted pyrroles by altering the reaction conditions slightly.

Ruthenium-catalyzed oxidative C-H bond olefination of N-methoxybenzamides using an oxidizing directing group.

Ruthenium-catalyzed oxidative C-H bond olefination of N-methoxybenzamides using an oxidizing directing group with a broad substrate scope is reported. The reactions of N-methoxybenzamides with acrylates in MeOH and styrene (or norbornadiene) in CF(3)CH(2)OH afforded two types of products.

The intramolecular sp2 and sp3 C-H bond activation of (p-cymene)ruthenium(II) N-heterocyclic carbene complexes.

The intramolecular sp2 and sp3 C-H activated products, as well as the monometalated products, based on the "(p-cymene)Ru(NHC)" framework were synthesised by treatment of a series of NHCs (1-R-3-methylimidazol-2-ylidene [R=Ph (1), Bn (2), t-Bu (3), i-Pr (4), Mes (5), Cy (6)] and 1,3-bis(isopropyl)imidazol-2-ylidene (7)) with [(p-cymene)RuCl2]2 under mild conditions. A new NHC precursor (1-tert-butyl-3-phenyl-4,5-dihydro-imidazol-2-ylidene) was also designed to compare the reactivity of sp2 C-H and sp3 C-H bonds upon cyclometalation, and only the sp3 C-H activated product (8) was observed. The factors that possibly determine the selectivity of intramolecular sp2 or sp3 C-H activation are elucidated by a series of experiments. In the cases where activation of both sp2 C-H and sp3 C-H is possible, steric factors overrode the others to dominate the regioselectivity of activation. All complexes were characterised by 1H NMR, 13C NMR and HRMS spectra. The molecular structures of 1, 3, 5, 6, 7, and 8 were confirmed by X-ray diffraction.

Reactions of indenyl-functionalized imidazolium salts and N-heterocyclic carbenes with Ru(3)(CO)(12).

Thermal treatment of indenyl-functionalized imidazolium salts and N-heterocyclic carbenes with Ru3(CO)12 gave different products. The normal mononuclear metal complexes (2a, 2b) were obtained via direct reaction of indenyl-functionalized imidazolium salts (1a, 1b) with Ru3(CO)12. Unexpected intramolecular C-H activated products (3a, 3b, 4a, 4b) were obtained via thermal treatment of corresponding indenyl-functionalized N-heterocyclic carbenes. All complexes were determined by 1H NMR, 13C NMR, IR spectra and elemental analysis. The molecular structures of 2b, 3a, 3b and 4b were determined by X-ray diffraction.

A general synthetic route to 6,6-substituted-6H-dibenzo[b,d]pyrans from dibenzofuran.

The reaction of dibenzofuran 1, lithium pieces (2.2 equiv), and TMEDA (2.2 equiv) in dry ether under reflux led to a solution of the corresponding C,O-dilithiated intermediate 2 which, upon treatment with different ketones or aldehydes (0.8 equiv) at -78 degrees C, afforded, after hydrolysis and dehydration, 6,6-substituted-6H-dibenzo[b,d]pyrans 3 in good yields. The reaction undergoes reductive ring opening and cyclization, and the intermediate diol 4e was isolated.

Synthesis and structures of cycloalkylidene-bridged cyclopentadienyl metallocene catalysts: effects of the bridges of ansa-metallocene complexes on the catalytic activity for ethylene polymerization.

A series of cycloalkylidene-bridged cyclopentadienyl metallocene complexes, [(CH(2))(n)C(C(5)H(4))(2)MCl(2)] (M = Ti, n = 4 (4), 5 (5), 6 (6); M = Zr, n = 4 (7), 5 (8), 6 (9); M = Hf, n = 4 (10), 5 (11), 6 (12)), have been synthesized and applied to ethylene polymerization after activation with methyl aluminoxane (MAO). The cycloalkylidene-bridged titanocene catalysts exhibit much higher activities than the corresponding zirconocene and hafnocene analogues, and have the highest activities at higher temperatures. In comparison, the silacyclopentylidene-bridged metallocene complexes [(CH(2))(4)Si(C(5)H(4))(2)MCl(2)] (M = Ti (13), Zr (14)) and isopropylene-bridged metallocene complexes [Me(2)C(C(5)H(4))(2)MCl(2)] (M = Ti (15), Zr (16)) have also been synthesized and applied to ethylene polymerization. In both cases, the titanocene complexes show much higher activities than the corresponding zirconocene analogues, especially at a lower temperature. The molecular structures of complexes 4-9 have been determined by X-ray diffraction. The structure-activity relationships, especially the effects of the bridges of ansa-metallocene complexes, are discussed.