N-Alkylation of amines with primary/secondary alcohols using a novel cobalt(II) inverse triazolyl-pyridine complex

Herein, we report a highly effective homogeneous methodology for the N-alkylation of amines with primary and secondary alcohols using a Co(II)-complex of an inverse triazolyl-pyridine ligand. The developed methodology tolerates various functional groups to produce the desired N-alkylated products in up to 98% yield. A number of control experiments establish that the developed methodology follows a hydrogen auto-transfer (HAT) pathway.

A sustainable strategic approach for N-alkylation of amines with activation of alcohols triggered via a hydrogen auto-transfer reaction using a Pd(II) complex: evidence for metal-ligand cooperativity

This work describes a new well-defined, air-stable, phosphine free palladium(II) [Pd(L)Cl] (1) catalyst. This catalyst was utilized for N-alkylation of amines and indole synthesis where H2O was found to be the by-product. A broad range of aromatic amines were alkylated using this homogeneous catalyst with a catalyst loading of 0.1 mol%. Greener aromatic and aliphatic primary alcohols were utilized and a hydrogen auto-transfer strategy via a metal-ligand cooperative approach was investigated. The precursor of the antihistamine-containing drug molecule tripelennamine was synthesized on a gram scale for large-scale applicability of the current synthetic methodology. A number of control experiments were performed to investigate the possible reaction pathway and the outcomes of these experiments indicated the azo-chromophore as a hydrogen reservoir during the catalytic cycle.

Ligand effect of cyclometallated iridium(iii) complexes on N-alkylation of amines in hydrogen borrowing reactions

Dinuclear iridium complexes with the general formula (C^N)2Ir(μ-Cl)2Ir(C^N)2 (C^N = bidentate ligand with carbon and nitrogen donor atoms) were prepared and used in catalytic systems for N-alkylation of amines through the hydrogen borrowing pathway. Triphenylphosphine derivatives were used as auxiliary in catalytic systems to provide excellent conversion of amines to N-alkylation products in yields ranging from 57% to 100%. The catalytic ability of the catalyst depends on the structure of its coordination ligands, including bidentate ligands (C^N) and triphenylphosphine derivatives. These catalytic systems adopt an environmentally friendly and sustainable reaction process through a hydrogen self-transfer strategy, using readily available alcohols as alkylating agents without the need for bases, solvents, and other additives, showing potential in the synthetic and pharmaceutical industries.

Selective Synthesis of Ketones and Chiral Allylic Alcohols from the Addition of Arylboronic Acids to α,β-Unsaturated Aldehydes Mediated by a Transition Metal/Monophosphorus Ligand System

Here, we demonstrated a transition metal-mediated/monophosphorus ligand system for the selective synthesis of ketones or chiral allylic alcohols in high yields/enantiomeric excess from the 1,2-addition of arylboronic acids to α,β-unsaturated aldehydes. Notably, isomerization of the chiral allylic alcohols to ketones was suppressed by the Ru-catalyzed/monophosphorus ligand system. The asymmetric catalytic system provides an alternative and efficient method of preparing chiral allylic alcohols.

Solvent/metal-free benzimidazolium-based carboxyl-functionalized porphyrin photocatalysts for the room-temperature alkylation of amines under the irradiation of visible light

The improvement of novel sustainable catalytic methods for green chemical production is an emergent area in chemical science.

Reductive Aldol-type Reactions in the Synthesis of Pharmaceuticals

The efficient chemo-, regio- and stereoselective formation of saturated carbon-carbon fragment is the critical challenge of organic synthesis; therefore, developing new methods for formation of these bonds is paramount. The rising interest for reductive aldol-type reactions is conditioned by its versatile applications, allowing the efficient formation of carbon-carbon bonds. The review aims to highlight the advantages and disadvantage of reductive aldol-type reactions to total synthesis of pharmaceutical substances in order to summarize knowledge and encourage further investigation of the field.

Unveiling the catalytic nature of palladium-N-heterocyclic carbene catalysts in the α-alkylation of ketones with primary alcohols

We report herein the synthesis of four new Pd-PEPPSI complexes with backbone-modified N-heterocyclic carbene (NHC) ligands and their application as catalysts in the α-alkylation of ketones with primary alcohols using a borrowing hydrogen process and tandem Suzuki-Miyaura coupling/α-alkylation reactions. Among the synthesized Pd-PEPPSI complexes, complex 2c having 4-methoxyphenyl groups at the 4,5-positions and 4-methoxybenzyl substituents on the N-atoms of imidazole exhibited the highest catalytic activity in the α-alkylation of ketones with primary alcohols (18 examples) with yields reaching up to 95%. Additionally, complex 2c was demonstrated to be an effective catalyst for the tandem Suzuki-Miyaura-coupling/α-alkylation of ketones to give biaryl ketones with high yields. The heterogeneous nature of the present catalytic system was verified by mercury poisoning and hot filtration experiments. Moreover, the formation of NHC-stabilized Pd(0) nanoparticles during the α-alkylation reactions was identified by advanced analytical techniques.

First-Row Transition-Metal Catalyzed Acceptorless Dehydrogenation and Related Reactions: A Personal Account

The development of sustainable catalytic protocols that circumvent the use of expensive and precious metal catalysts and avoid toxic reagents plays a crucial role in organic synthesis. Indeed, the direct employment of simple and abundantly available feedstock chemicals as the starting materials broadens their synthetic application in contemporary research. In particular, the transition metal-catalyzed diversification of alcohols with various nucleophilic partners to construct a wide range of building blocks is a powerful and highly desirable methodology. Moreover, the replacement of precious metal catalysts by non-precious and less toxic metals for selective transformations is one of the main goals and has been paid significant attention to in modern chemistry. In view of this, the first-row transition metal catalysts find extensive applications in various synthetic transformations such as catalytic hydrogenation, dehydrogenation, and related reactions. Herein, we have disclosed our recent developments on the base-metal catalysis such as Mn, Fe, Co, and Ni for the acceptorless dehydrogenation reactions and its application in the C-C and C-N bond formation via hydrogen auto-transfer (HA) and acceptorless dehydrogenation coupling (ADC) reactions. These HA/ADC protocols employ alcohol as alkylating agents and eliminate water and/or hydrogen gas as by-products, representing highly atom-efficient and environmentally benign reactions. Furthermore, diverse simple to complex organic molecules synthesis by C-C and C-N bond formation using feedstock alcohols are also overviewed. Overall, this account deals with the contribution and development of efficient and novel homogeneous as well as heterogeneous base-metal catalysts for sustainable chemical synthesis.

A Novel Modified Cross-Coupling of Phenols and Amines Using Dichloroimidazolidinedione (DCID)

Phenols are considered as an ideal alternative to aryl halides as coupling partners in cross-coupling reactions. In the present work a copper-catalyzed cross-coupling of phenols with various aromatic and aliphatic amines for the synthesis of secondary aryl amines using dichloroimidazolidinedione (DCID) as a new and efficient activating agent has been developed. Substituted phenols were compatible with the standard reaction conditions. The two proposed mechanisms, which are based on the oxidation addition of copper with Ar-OMCID (MCID: Monochloroimidazolidinedione), are also discussed.

Efficient bifunctional reactivity of K-doped CrO(OH) nanosheets: exploiting the combined role of Cr(iii) and surface –OH groups in tandem catalysis

Layered K-α-CrO(OH) nanosheets as a non-noble metal based tandem catalyst for sequential oxidation and coupling/condensation reactions.

Mechanistic studies on the N-alkylation of amines with alcohols catalysed by iridium(i) complexes with functionalised N-heterocyclic carbene ligands

Experimental and theoretical studies give support for an iridium-catalyzed C–N bond formation.

Highly Selective Upgrading of Biomass-Derived Alcohol Mixtures for Jet/Diesel-Fuel Components

In light of the increasing concern about the energy and environmental problems caused by the combustion of petroleum-based fuels (e.g., jet and diesel fuels), the development of new procedures for their sustainable production from renewable biomass-derived platform compounds has attracted tremendous attention recently. Long-chain ketones/alcohols are promising fuel components owing to the fuel properties that closely resemble those of traditional fuels. The focus of this report is the production of long-chain ketones/alcohols by direct upgrading of biomass-derived short-chain alcohol mixtures (e.g., isopropanol-butanol-ethanol mixtures) in pure water. An efficient Pd catalyst system was developed for these highly selective transformations. Long-chain ketones/alcohols (C₈ -C₁₉ ), which can be used as precursors for renewable jet/diesel fuel, were obtained in good-to-high selectivity (>90 %) by using the developed Pd catalyst.

C-Alkylation by Hydrogen Autotransfer Reactions

The development of practical, efficient, and atom-economical methods for the formation of carbon-carbon bonds remains a topic of considerable interest in current synthetic organic chemistry. In this review, we have summarized selected topics from the recent literature with particular emphasis on C-alkylation processes involving hydrogen transfer using alcohols as alkylation reagents. This review includes selected highlights concerning recent progress towards the modification of catalytic systems for the α-alkylation of ketones, nitriles, and esters. Furthermore, we have devoted a significant portion of this review to the methylation of ketones, alcohols, and indoles using methanol. Lastly, we have also documented recent advances in β-alkylation methods involving the dimerization of alcohols (Guerbet reaction), as well as new developments in C-alkylation methods based on sp (3) C-H activation.

Ag@polypyrrole: A highly efficient nanocatalyst for the N-alkylation of amines using alcohols

We have synthesized Ag@polypyrrole nanomaterial by dispersing ultrafine silver nanoparticles (Ag NPs) over the organic polymer polypyrrole. The Ag@polypyrrole material has been characterized by powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), electron paramagnetic resonance (EPR), Fourier transform infrared (FT-IR), ultraviolet-visible absorption (UV-vis) and atomic adsorption spectroscopy (AAS), and thermogravimetric analysis (TGA). The XRD pattern suggested the cubic crystalline phase of Ag NPs in Ag@polypyrrole. TEM image analysis revealed that silver nanoparticles are highly dispersed in the polymer matrix. The Ag@polypyrrole acts as an efficient and versatile heterogeneous nanocatalyst in the N-alkylation of amines using alcohols. The catalyst can be easily prepared, highly robust and reused several times without decrease in its catalytic activity.