Cobalt–Rhodium Heterobimetallic Nanoparticle-Catalyzed N‑Alkylation of Amines with Alcohols to Secondary and Tertiary Amines

Without the requirement for base or other additives, Co₂Rh₂/C can selectively catalyze both mono- and bis-N-alkylation through the coupling of simple alcohols with amines, yielding a range of secondary and tertiary amines in good to excellent isolated yields. The reaction can be applied to benzyl alcohol with optically active 1-phenylethan-1-amines, and secondary amines were isolated in quantitative yields with an excellent enantiomeric excess (ee > 94%). Selectivity is achieved by varying the reaction temperature and amount of catalyst used. This catalytic system has several advantages including eco-friendliness and a simple workup procedure. The catalyst can be successfully recovered and reused ten times without any significant loss of activity

Rhodium-Catalyzed Carbonylative [3 + 2 + 1] Cycloaddition of Alkyne-Tethered Alkylidene­cyclo­propanes to Phenols in the Presence of Carbon Monoxide

A novel Rh-catalyzed carbonylative [3 + 2 + 1] cycloaddition of alkyne-tethered alkylidene­cyclopro­panes for the facile synthesis of bicyclic phenols in high yields has been developed. The reaction tolerated carbon and heteroatoms in the tether

Transition-Metal-Free Poly(thiazolium) Iodide/1,8-Diazabicyclo[5.4.0]undec-7-ene/Phenazine-Catalyzed Esterification of Aldehydes with Alcohols

Poly­(3,4-dimethyl-5-vinylthiazolium) iodide was used as a polymer precatalyst in the presence of 1,8-diazabicyclo[5.4.0]­undec-7-ene (DBU) and phenazine for the oxidative esterification of aldehydes with alcohols. Selective functionalization of OH groups was achieved in the presence of NH₂ groups. The poly­(thiazolium) iodide/DBU/phenazine system exhibited excellent catalytic activity and could be reused five times without loss of activity

Hydrogen-Free Cobalt–Rhodium Heterobimetallic Nanoparticle-Catalyzed Reductive Amination of Aldehydes and Ketones with Amines and Nitroarenes in the Presence of Carbon Monoxide and Water

Cobalt–rhodium heterobimetallic nanoparticle-catalyzed reductive amination of aldehydes and ketones with amines in the presence of 5 atm carbon monoxide without an external hydrogen source has been developed. Water added and generated in situ produces hydrogen via a water–gas-shift reaction. The reaction can be extended to the tandem reduction of aldehydes and ketones with nitroarenes. The catalytic system is stable under the reaction conditions and could be reused eight times without losing any catalytic activity

Palladium(II)-Catalyzed Transformation of 3‑Alkylbenzofurans to [2,3′-Bibenzofuran]-2′(3′H)-ones: Oxidative Dimerization of 3‑Alkylbenzofurans

An unprecedented oxidative dimerization by palladium catalysis has been developed using PhI­(OPiv)₂ as a by-standing oxidant. This provides a facile method for the synthesis of quaternary 2,3′-bibenzofuran-2′(3′)-ones from readily accessible substrates. A plausible mechanism involving a Pd­(II)–Pd­(IV) catalytic cycle is proposed; a trace amount of water is required for subsequent oxidation

Bimetallic Cobalt–Rhodium Nanoparticle-Catalyzed Reductive Amination of Aldehydes with Nitroarenes Under Atmospheric Hydrogen

A cobalt–rhodium heterobimetallic nanoparticle (Co₂Rh₂/C)-catalyzed tandem reductive amination of aldehydes with nitroaromatics to sec-amines has been developed. The tandem reaction proceeds without any additives under mild conditions (1 atm H₂ and 25 °C). This procedure can be scaled up to the gram scale, and the catalyst can be reused more than six times without loss of activity

Rhodium-Catalyzed Intermolecular Carbonylative [2 + 2 + 1] Cycloaddition of Alkynes Using Alcohol as the Carbon Monoxide Source for the Formation of Cyclopentenones

A highly regioselective rhodium-catalyzed intermolecular carbonylative [2 + 2 + 1] cycloaddition of alkynes using alcohol as a CO surrogate to access 4-methylene-2-cyclopenten-1-ones has been developed. In this transformation, the alcohol performs multiple roles, including generating the Rh–H intermediate, functioning as the CO source, and assisting in the isomerization of the alkyne. Alkynes can act as both the olefin and the alkyne partner in the cyclopentenone core

Phosphine-Free Palladium-Catalyzed Direct Bisarylation of Pyrroles with Aryl Iodides on Water

The Pd-catalyzed bisarylation of pyrroles with aryl iodides on water is described. The reaction proceeds under mild reaction conditions, i.e., relatively low temperature (40 °C) and phosphine-free

Phosphine-Free Palladium-Catalyzed Direct Bisarylation of Pyrroles with Aryl Iodides on Water

The Pd-catalyzed bisarylation of pyrroles with aryl iodides on water is described. The reaction proceeds under mild reaction conditions, i.e., relatively low temperature (40 °C) and phosphine-free

Probing Ground-to-CT State Electronic Coupling for the System with No Apparent Charge Transfer Absorption Intensity by Ultrafast Visible-Pump/Mid-IR-Probe Spectroscopy

New π-stacked [Ru(tpy)₂]²⁺ (<b>T_T</b>)-benzoquinone (Q) donor–acceptor (D–A) systems, [Ru(6-(2-cyclohexa-2′,5′-diene-1,4-dione)-2,2′:6′,2″-terpyridine)(2,2′:6′,2″-terpyridine)][PF₆]₂ (<b>TQ_T</b>), and [Ru(6-(2-cyclohexa-2′,5′-diene-1,4-dione)-2,2′:6′,2″-terpyridine)(4′-phenyl-2,2′:6′,2″-terpyridine)][PF₆]₂ (<b>TQ_TPh</b>) have been synthesized and characterized. Orthogonal alignment of Q to the tpy ligand imposes this unit juxtaposed cofacially on the central pyridyl ring in another tpy with a typical van der Waals distance. The low-energy electronic absorptions of these complexes are mainly metal-to-ligand charge transfer (MLCT) in nature, similar to that observed in <b>T_T</b> benchmark system, and do not exhibit distinguishable metal-to-Q charge transfer (MQCT) absorption in spite of the proximal location of the electron acceptor unit (Q) to the electron donor unit (<b>T_T</b>). TD-DFT calculation supports the experimental results that the collective oscillator strength of MQCT bands remains ∼0.002. Due to the negligible intensity of MQCT bands, evaluation of <i>H</i>_DA between the ground and the lowest energy MQCT states are not available through conventional Mulliken–Hush analysis. For such systems, <i>H</i>_DA values were successfully evaluated from the relative difference (ξ) of the carbonyl stretching frequency between the neutral Q and its one-electron radical anion, which was determined by an ultrafast visible-pump/mid-IR-probe (TrIR) spectroscopic method. TrIR results showed that the partial charge localized on the Q moiety in the MQCT state was ca. −0.97<i>e</i>, and the corresponding <i>H</i>_DA was ∼1600 cm^–1. This value was in good agreement with that estimated by the Mulliken population analysis of the ground-state geometry