Liandi Wang

Pt-Sn/γ-Al2O3-catalyzed highly efficient direct synthesis of secondary and tertiary amines and imines.

Versatile syntheses of secondary and tertiary amines by highly efficient direct N-alkylation of primary and secondary amines with alcohols or by deaminative self-coupling of primary amines have been successfully realized by means of a heterogeneous bimetallic Pt-Sn/γ-Al(2)O(3) catalyst (0.5 wt % Pt, Pt/Sn molar ratio=1:3) through a borrowing-hydrogen strategy. In the presence of oxygen, imines were also efficiently prepared from the tandem reactions of amines with alcohols or between two primary amines. The proposed mechanism reveals that an alcohol or amine substrate is initially dehydrogenated to an aldehyde/ketone or NH-imine with concomitant formation of a [PtSn] hydride. Condensation of the aldehyde/ketone species or deamination of the NH-imine intermediate with another molecule of amine forms an N-substituted imine which is then reduced to a new amine product by the in-situ generated [PtSn] hydride under a nitrogen atmosphere or remains unchanged as the final product under an oxygen atmosphere. The Pt-Sn/γ-Al(2)O(3) catalyst can be easily recycled without Pt metal leaching and has exhibited very high catalytic activity toward a wide range of amine and alcohol substrates, which suggests potential for application in the direct production of secondary and tertiary amines and N-substituted imines.

A Versatile Ruthenium(II)–NNC Complex Catalyst for Transfer Hydrogenation of Ketones and Oppenauer‐Type Oxidation of Alcohols

A ruthenium(II)-NNC pincer complex containing an unsymmetrical tridentate pyrazolyl-pyridyl-tolyl ligand was synthesized and structually characterized. This complex exhibited excellent catalytic activity for the transfer hydrogenation of ketones in 2-propanol at reflux, and for the Oppenauer-type dehydrogenative oxidation of alcohols in acetone at reflux (see scheme).

Iron-Promoted Cyclization/Halogenation of Alkynyl Diethyl Acetals

FeCl(3)- and FeBr(3)-promoted cyclization/halogenation of alkynyl diethyl acetals has been efficiently realized, selectively affording (E)-2-(1-halobenzylidene or alkylidene)-substituted five-membered carbo- and heterocycles which were then efficiently transformed to vinylarenes by Suzuki coupling. The present protocol has provided a new alternative route to vinylic C-Cl and C-Br bond formation.

Copper-Mediated Intramolecular Oxidative C–H/C–H Cross-Coupling of α-Oxo Ketene N,S-Acetals for Indole Synthesis

CuCl2-mediated intramolecular C-H/C-H cross-dehydrogenative coupling (CDC) of thioalkyl-substituted α-acetyl or α-aroyl ketene N,S-acetals afforded 2-thioalkyl indoles. Tunable C-S bond transformations of the resultant indoles led to highly functionalized N-heterocyclic compounds. A β-thioalkyl is necessary to activate the N,S-acetal substrate and enable the CDC reaction to occur, and the relevant mechanism studies revealed that the CDC reaction follows a radical pathway.

Effect of Alumina Support on Catalytic Performance of Pt-Sn/Al2O3 Catalysts in One-Step Synthesis of N-Phenylbenzylamine from Aniline and Benzyl Alcohol

The effect of alumina on the catalytic performance of Pt‐Sn/Al2O3 catalysts in the green synthesis of secondary amines by N‐alkylation of amines with alcohols based on the borrowing hydrogen strategy was investigated. N‐alkylation of aniline with benzyl alcohol to produce N‐phenylbenzylamine was used as a model reaction. Three different alumina supports were selected, and the corresponding catalysts were prepared by complex impregnation under vacuum. The supports and catalysts were characterized using N2 adsorption‐desorption, mercury intrusion porosimetry, X‐ray diffraction, transmission electron and scanning electron microscopies, CO chemisorption, H2 temperature‐programmed reduction, and NH3 temperature‐programmed desorption. The results show that the catalysts with small Pt particles that were highly dispersed on the alumina supports and interacted weakly with the supports had high catalytic activities. The large pore volumes and pore size distributions of the alumina supports helped diffusion and adsorption of the reactants on the catalyst surface and increased the catalytic activity; they also promoted removal of the products from the catalyst surface and enhanced the catalytic stability. However, strong acidity and acid distribution of the alumina supports decreased the selectivity for secondary amines and reduced the catalyst stability.

Brønsted acid catalyzed PhSe transfer versus radical aryl transfer: linear codimerization of styrenes and internal olefins.

Brønsted acid p-TsOH·H2O-catalyzed hydrovinylation of styrenes with internal olefins α-oxo ketene dithioacetals was efficiently achieved in the presence of N-phenylselenophthalimide (N-PSP), regioselectively affording Markovnikov phenylselenative hydrovinylation products through PhSe transfer of the phenylseleno ketene dithioacetal intermediates. Radical reduction of the resultant PhSe-alkyl-substituted ketene dithioacetals with AIBN/n-Bu3SnH gave the corresponding anti-Markovnikov hydrovinylation products formally from the linear codimerization of styrenes and the internal olefins.

Iron-Promoted Difunctionalization of Alkenes by Phenylselenylation/1,2-Aryl Migration

Iron-promoted difunctionalization of α,α-diaryl and α-aryl-α-alkyl allylic alcohols has been efficiently achieved by means of N-(phenylseleno)phthalimide (N-PSP) under mild conditions. An in situ generated phenylselenium cation (PhSe+) was added to the olefinic C═C bond to initiate the regioselective phenylselenylation with concomitant 1,2-aryl migration, following a migration preference contrary to the well-known radical pathway. Hydrazonation of the resultant alkene difunctionalization products, that is, α-aryl-β-phenylselenyl ketones, and subsequent copper-catalyzed dehydroselenylation efficiently afforded functionalized 2-pyrazoline derivatives.

Ruthenium(II) complex catalysts bearing a 2,6-bis(tetrazolyl)pyridine ligand for the transfer hydrogenation of ketones

Article history: Received 1 November 2017 Accepted 1 December 2017 Published 5 February 2018 Three ruthenium(II) complex catalysts bearing 2,6‐bis(tetrazolyl)pyridine were synthesized, struc‐ turally characterized, and applied in the transfer hydrogenation of ketones. Their different catalytic activities were attributed to the different phosphine ligands on the 4‐chloro‐2,6‐bis(1‐(p‐tolyl)‐ 1H‐ tetrazol‐5‐yl)pyridine ruthenium(II) complexes, with that based on 1,4‐ bis(diphenylphosphino) butane exhibiting better catalytic activity. A variety of ketones were reduced to their corresponding alcohols with >95% conversion.

Correction: Copper-mediated intramolecular oxidative C–H/N–H cross-coupling of α-alkenoyl ketene N,S-acetals to synthesize pyrrolone derivatives

Correction for ‘Copper-mediated intramolecular oxidative C–H/N–H cross-coupling of α-alkenoyl ketene N,S-acetals to synthesize pyrrolone derivatives’ by Fei Huang et al., Chem. Commun., 2014, DOI: 10.1039/c4cc05837b.