Rhodium(III)-catalyzed direct C-7 sulfonamidation and amination of indolines with arylsulfonamides and trifluoroacetamide

A rhodium-catalyzed direct C–H sulfonamidation and amidation of C-7 position of indolines by simple and commercially available arylsulfonamides and trifluoroacetamide has been developed, affording a series of N-arylsulfonamides and N-aryltrifluoroacetamides in moderate to excellent yields, respectively. Notably, this catalytic system is highly convenient on mmol scale.     

Palladium(II)-catalyzed aerobic intramolecular allylic CH activation for the synthesis of indolines

A method for the preparation of indolines via palladium-catalyzed aerobic intramolecular allylic CH activation was developed. Oxygen was successfully used as oxidant with catalytic amount of 1,4-benzoquinone. 16 examples were reported, the majority of substrates gave moderate to good yields.     

Enzyme catalyzed hydroxymethylation of aromatic aldehydes with formaldehyde. Synthesis of hydroxyacetophenones and (S)-benzoins

Benzaldehyde lyase from the Pseudomonas Fluorescens catalyzed reaction of aromatic aldehydes with formaldehyde providing 2-hydroxy-1-arylethan-1-one in high yields via an acyloin linkage. Kinetic resolution of rac-benzoins with formaldehyde providing (S)-benzoins and 2-hydroxy-1-arylethan-1-one via C-C bond cleavage and a bond formation reaction.     

Pd(II)-catalyzed enantioselective intramolecular oxidative amination utilizing (+)-camphorsulfonic acid

An enantioselective Pd(II)-catalyzed intramolecular oxidative amination reaction was developed utilizing the commercially available chiral X-type ligand (1S)-(+)-camphorsulfonic acid. The Wacker-type cyclization produced chiral indoline products with enantioselectivies up to 45% ee. Electronic structure calculations employing density functional theory support a trans-aminopalladation mechanism.     

A novel synthesis of indolines by reaction of ortho-nitrophenylmalonates with bis(dimethylamino)methane

We report here a new and efficient synthesis of substituted indolines via reaction of dimethyl 2,4-dinitrophenyl-(2,4,6-trinitrophenyl)malonates with bis(dimethylamino)methane.     

Brønsted acid-catalyzed radical CH functionalization of acetone with N-allyl anilines to give 3-(3-oxobutyl)indolines

K₂S₂O₈ was unprecedentedly used instead of tert-butyl hydroperoxide (TBHP) in Brønsted acid-assisted catalytic strategy for ketonic radical generation, and the first Brønsted acid-catalyzed radical CH functionalization of acetone across unactivated alkenes is presented. In the presence of TsOH and K₂S₂O₈, N-allyl anilines underwent addition/cyclization cascade with acetone to afford 3-(3-oxobutyl)indolines with exo-selectivity and broad substrate scope at a relatively low temperature.     

Titanocene(III)-catalyzed formation of indolines and azaindolines

Reductive cyclization of epoxides tethered to substituted anilines and aminopyridines in the presence of 3 mol % of titanocene dichloride and stoichiometric manganese metal promotes a radical annulation to form 3,3-disubstituted indolines and azaindolines.     

A convenient method for the Ru(0)-catalyzed regioselective deuteration of N-alkyl-substituted anilines

A highly effective and operationally practical method for the regioselective deuteration of N-alkyl-substituted anilines employing Ru₃(CO)₁₂ (?1 mol %) as catalyst and D₂O as deuterium source was described. A variety of N-alkyl-substituted anilines were efficiently deuterated (up to 98%) at the ortho and/or para position with respect to the nitrogen at neutral conditions. Under the present conditions, deuterated anilines can be easily obtained with simple extraction and evaporation. Substituents with aromatic methoxy groups would not influence the selectivity compared to previous method.     

Ru(II)-catalyzed asymmetric cyclopropanation using chiral diphenylphosphino(oxazolinyl)quinoline ligands

Several chiral 8-diphenylphosphino-2-oxazolinylquinolines were synthesized starting from 2-cyano-8-hydroxyquinoline. These N,N,P-chelates were successfully employed in the Ru(II)-catalyzed asymmetric cyclopropanation reactions of diazo-alkenes. The catalytic system exhibited good reactivity and high thermal stability and provided high yields in the intramolecular cyclopropanation, albeit somewhat decreased enantioselectivities compared to known catalytic systems. A dramatic dependency of the enantioselectivity on the substituents of the oxazoline ring was observed.     

Scope of Ru(II)-catalyzed synthesis of pyridines from alkynes and nitriles

Pyridines can be efficiently synthesized by Ru(II)-catalyzed [2 + 2 + 2] cycloaddition of 1,6-diynes to alpha,omega-dinitriles or electron-deficient nitriles or by Ru(II)-catalyzed [2 + 2 + 2] cocyclization of electron-deficient alkynes and electron-deficient nitriles. The reactions with dinitriles seem likely to proceed via ruthenacyclopentadiene intermediates and the reactions with electron-poor nitriles via azaruthenacyclopentadienes. The reaction with asymmetric electron-deficient alkynes affords 2,3,6-trisubstituted pyridines in good yield.     

三价铑催化硝酮与炔的碳氢活化偶联合成二氢吲哚

三价铑在氧化还原中性条件下催化硝酮与炔发生偶联,经过氮芳环的碳氢键活化和氧转移可以高化学选择性、中等到良好非对映选择性的得到三取代二氢吲哚。     

Room-temperature Ru(II)-catalyzed transfer hydrogenation of ketones and aldehydes in air

Transfer hydrogenation (TH) of ketones and aldehydes was efficiently carried out in 2-propanol at room temperature by means of a ruthenium(II) complex catalyst bearing a 2-(benzoimidazol-2-yl)-6-(pyrazol-1-yl)pyridine ligand. TH of the ketone substrates proceeded in air, reaching final TOFs of up to 59,400 h⁻¹, and the reduction of aldehydes proceeded under a nitrogen atmosphere to achieve final TOFs of up to 5940 h⁻¹.     

Ru(II)-catalyzed chemo- and regioselective cyclotrimerization of three unsymmetrical alkynes through boron temporary tether. One-pot four-component coupling via cyclotrimerization/Suzuki-Miyaura coupling

The Ru(II)-catalyzed [2+2+2] cyclotrimerization of alkynylboronates, propargyl alcohol, and terminal alkynes proceeded chemo- and regioselectively to give rise to arylboronates, which were subjected to Suzuki-Miyaura cross-coupling with aryliodides to afford highly substituted biaryls in 53-76% yields.     

Pd(II)-catalyzed enantioselective oxidative tandem cyclization reactions. Synthesis of indolines through C-N and C-C bond formation

We have developed an efficient Pd(II)-catalyzed enantioselective oxidative tandem cyclization strategy using molecular oxygen as a green oxidant for the double 5-exo-trig cyclizations of N-(2-allylaryl) amides to afford a variety of indolines in good yields without the formation of undesired monocyclization products. By employing Pd(TFA)2/(-)-sparteine as the chiral catalyst, we obtained tandem cyclization products with high enantioselectivity (up to 91% ee).     

Pd(II)-catalyzed regioselective direct arylation of uracil via oxidative Heck reaction using arylboronic acids

A palladium catalyzed regioselective synthesis of 6-aryl uracils via oxidative Heck reaction (C–H bond functionalization) of uracils and arylboronic acids is reported. The method is simple, atom-economical, and high yielding.     

Ru(II)-catalyzed cascade reactions in stereocontrolled construction of rigid as-indacene-bridged bis(alpha-amino acid) derivatives

The key construction in the preparation of as-indacene-bridged bis(alpha-amino acid) derivatives was effected by a Ru(II)-catalyzed RCM cascade reaction of appropriately substituted triynes. The latter were available after stepwise and stereocontrolled alkynylations of (2R)-2,5-dihydro-2-isopropyl-3,6-dimethoxypyrazine as chiral auxiliary. The regio- and stereochemical transformations have been verified by a single-crystal X-ray analysis.     

Mechanism of Ru(II)-catalyzed olefin insertion and C-H activation from quantum chemical studies

The mechanism of catalytic hydroarylation of olefins by the homogeneous Ru(Tp)(CO)(Ph)(NCCH3) catalyst recently reported by Gunnoe et al. is characterized using quantum mechanics (density functional theory). The catalytic cycle features two key steps, 1,2-olefin insertion and C-H activation via an unusual mechanism, oxidative hydrogen migration. We find that these two key steps are competitive and that improving the rate of one step is detrimental to the rate of the other. The Ru catalyst has better balance and consequently higher activity than the previously explored Ir-based system.     

Rhodium(I)-catalyzed regioselective additions of chloroformates to 1,2-dienes

Rhodium phosphine complexes catalyze addition of chloroformates to terminal allenes to afford β-chloro-β,γ-unsaturated esters.     

Synthesis of cyanoalkyl indolines through cyanoalkylarylation of N-allyl anilines with alkyl nitriles under metal-free and neutral conditions

An α-C(sp³)−H functionalization of alkyl nitriles under metal-free and neutral conditions is presented. In the presence of di-tert-butyl peroxide (DTBP), N-allyl anilines underwent exo-selective cyanoalkylation/cyclization cascade, providing a direct access to 3-cyanoalkyl indolines. Previously, a transition-metal catalyst and/or a strong base were generally required to activate nitrilic α-C−H bonds. This reaction features a broad substrate scope and low cost, and primary, secondary and tertiary indolin-3-yl nitriles could all be assembled.