Acceptorless Dehydrogenative Coupling Research Articles

Cu-UiO-66 Catalyzed Synthesis of Imines via Acceptorless Dehydrogenative Coupling of Alcohols and Amines.

Herein, the Cu-UiO-66 catalyst was developed for acceptorless dehydrogenative coupling (ADC) between alcohols and amines to produce imines. The Cu-UiO-66 catalyst was synthesized by installing Cu2+ onto Zr-oxo clusters in UiO-66, and the catalyst efficiently catalyzes the ADC reaction under mild and environmentally friendly conditions with excellent selectivity. Mechanistic studies reveal that the O2·- radicals and porosity of formed in Cu-UiO-66 participate cooperatively during the catalytic cycle. Meanwhile, the only by-product of the system is environmentally benign water. Cycling tests and hot filtration tests showed that the Cu-UiO-66 catalyst exhibited excellent stability and catalytic activity during the reaction. Importantly, the Cu-UiO-66 catalyst might provide a promising strategy for the ADC reaction between alcohols and amines to produce imines.

Ruthenium-Catalyzed Synthesis of 2-Pyrazolines via Acceptorless Dehydrogenative Coupling of Allylic Alcohols with Hydrazines.

Described herein is the synthesis of 2-pyrazolines via acceptorless dehydrogenative coupling of allylic alcohols with hydrazines based on a Ru3(CO)12/NHC-phosphine-phosphine ligand L catalytic system. The reaction not only exhibits low catalyst loading (only 0.3 mol %), wide substrate scope, good to excellent yields, and high selectivity but also omits the use of sacrificial hydrogen acceptor with only H2 and H2O as byproducts, making the reaction green and atom-economical.

Cobalt Nanoparticles Catalyzed N-Heterocycles Synthesis via Acceptorless Dehydrogenative Coupling.

The acceptorless dehydrogenation reaction is a sustainable and atom-economical methodology in organic synthesis, resulting in the byproducts of only hydrogen or water. Herein, a robust Co-Si/CN catalyst (derived from ZIF@SiO2 composite) has been synthesized through a one-step assembly process via pyrolysis and etching. This catalyst has been employed for the acceptorless dehydrogenative coupling of 2-aminoalcohols with secondary alcohols, enabling efficient conversion of various substrates into desired quinoline or pyridine derivatives with a yield of up to 94 %.

Acceptorless Dehydrogenation under Neat Reaction Conditions: Synthesis of 2-Aryl/Alkyl Quinazolinones Using Supported Ni NPs as Catalyst

AbstractWe report here a Ni-NPs-catalyzed one-pot synthesis of 2-alkyl/aryl quinazolinone motifs via acceptorless dehydrogenation of alcohol, condensation of an aldehyde intermediate with 2-aminobenzamide, followed by a second dehydrogenation of the cyclized intermediate. The protocol is atom-economical and require earth-abundant Ni as the catalyst. The present report involves the annulation of 2-aminobenzamide with various types of primary alcohols, including aryl/heteroaryl methanol, and aliphatic alcohols, and produces high yields of the desired products under neat conditions. The catalyst was synthesized via a high-temperature pyrolysis strategy, using ZIF-8 as the sacrificial template. The Ni NPs@N-C catalyst was characterized by XPS, HR-TEM, HAADF-STEM, XRD, and ICP-MS. The catalyst is stable even in air at room temperature and displayed excellent activity in the acceptorless dehydrogenative coupling synthesis of quinazolinones and could be recycled five times without appreciable loss of its activity.

Single-Atom Fe-Catalyzed Acceptorless Dehydrogenative Coupling to Quinolines.

A single-atom iron catalyst was found to exhibit exceptional reactivity in acceptorless dehydrogenative coupling for quinoline synthesis, outperforming known homogeneous and nanocatalyst systems. Detailed characterizations, including aberration-corrected HAADF-STEM, XANES, and EXAFS, jointly confirmed the presence of atomically dispersed iron centers. Various functionalized quinolines were efficiently synthesized from different amino alcohols and a range of ketones or alcohols. The iron single-atom catalyst achieved a turnover number (TON) of up to 105, far exceeding the results of current homogeneous and nanocatalyst systems. Detailed mechanistic studies verified the significance of single-atom Fe sites in the dehydrogenation process.

Direct use of methanol instead of formaldehyde or paraformaldehyde: Acceptorless dehydrogenative coupling for the synthesis of arylhydrazones catalyzed by a metal–ligand iridium bifunctional catalyst

The strategy of the synthesis of arylhydrazones via acceptorless dehydrogenative coupling of arylhydrazines with methanol was proposed and accomplished. In the presence of [Cp*Ir(2,2′-bpyO)(H2O)] (0.5 mol %), a series of desirable products were obtained in high yields. It was found that functional groups in bpy are crucially important for the catalytic activity of iridium complexes. Furthermore, DFT calculations and mechanistic experiments were presented. Notably, this research exhibits the potential of direct use of methanol instead of formaldehyde or paraformaldehyde for organic synthesis.

Cobalt-catalyzed Synthesis of Alkenes and Vinyl Sulfones via Dehydrogenative Coupling of Alcohols and Sulfones.

A novel protocol to access vinyl sulfones and internal/terminal olefins via cobalt-catalyzed acceptorless dehydrogenation coupling (ADC) has been established. This system enables the divergent synthesis of three kinds of olefin compounds through the coupling of alcohols and sulfones under oxidant-free conditions. The broad applicability of this procedure is demonstrated by over forty olefin products, including pharmaceutical-related compounds and complex substrates, in a one-pot process. Preliminary mechanistic studies were conducted, and a proposed reaction pathway was presented.

Dehydrogenative Coupling of Alkylamines with Primary Alcohols Forming α-Amino Ketones.

Acceptorless dehydrogenative coupling reactions between C-H bonds offer straightforward and atom-economical methods connecting readily available materials while liberating gaseous hydrogen as the sole byproduct. Despite the growing interest in such transformations, their realization still poses a significant challenge. Here we report a photoinduced dehydrogenative coupling reaction of alkylamines with primary alcohols. C-H bonds adjacent to nitrogen and oxygen are site-selectively cleaved, and a C-C bond is created between the carbon atoms in a cross-selective manner to produce α-amino ketones. Diverse polar functionalities such as esters, amides, and carboxylic acids survived, demonstrating the broad applicability of the present method.

Divergent Synthesis of Pyrazoles via Manganese Pincer Complex Catalyzed Acceptorless Dehydrogenative Coupling Reactions.

This report detailed the synthesis of multi-substituted pyrazoles through the acceptorless dehydrogenative coupling (ADC) reaction catalyzed by a well-defined manganese(I)-pincer complex. Symmetrically substituted pyrazoles were synthesized by reacting 1,3-diols with hydrazines. Unsymmetrically substituted pyrazoles were selectively made via the ADC of primary alcohols with methyl hydrazones. Water and hydrogen are liberated as the green byproducts. The endurance of these methodologies has been presented by producing 30 substrates with varied functionalities. Model reactions were scaled up to demonstrate practicability. The reaction rate and order were measured to transparent the involvement of the reagents during catalysis. Control experiments elucidated the plausible reaction mechanisms.

Dinuclear Ru(II) Schiff Base Complex Catalyzed One-Pot Synthesis of Quinolines through Acceptorless Dehydrogenative Coupling of Secondary Alcohols with 2-Nitrobenzyl Alcohol

Dinuclear Ru(II) Schiff Base Complex Catalyzed One-Pot Synthesis of Quinolines through Acceptorless Dehydrogenative Coupling of Secondary Alcohols with 2-Nitrobenzyl Alcohol

Synthesis of 2-substituted quinoline derivatives using [RuCl2(p-cymene)]2-ferrocene thioamide catalytic system via acceptorless dehydrogenative coupling

The substituted quinolines were synthesized via acceptorless dehydrogenative coupling (ADC) of 2-aminobenzyl alcohol with ketones/secondary alcohols, which was accomplished using the in situ catalytic activity of [RuCl2(p-cymene)]2 and ferrocene thioamide (Fc-TA) ligands. The catalysis was extended to aromatic and heterocyclic ketones and secondary alcohols, with unsubstituted and chloro‑substituted 2-aminobenzyl alcohols. The Fc-TA ligands (L1-L3) were synthesized, and characterized using spectroscopic techniques such as FT-IR, UV–Vis, NMR and HRMS. The influence of ligands on the catalysis was studied. Overall, the synthesis of quinolines was accomplished with good to moderate yields, via both mono and double dehydrogenation reactions along with hydrogen and water as only by-products.

Molybdenum Catalyzed Acceptorless Dehydrogenation of Alcohols for the Synthesis of Quinolines

AbstractThe first molybdenum triazolylidene complexes catalyzing the atom‐economical synthesis of quinolines through acceptorless dehydrogenative coupling of alcohols is reported. A new family of Mo(0) complexes bearing chelating bis‐1,2,3‐triazolylidene, pyridyl‐1,2,3‐triazolylidene, and bis‐triazole ligands have been prepared and applied as catalysts for the synthesis of quinolines. Interestingly, Mo complexes bearing bis‐1,2,3‐triazolylidene ligands with alkyl groups (Et, n‐Bu) displayed superior catalytic activities than those containing aryl substituents on the triazolylidene rings. Control experiments corroborated that the catalytic reaction involves the dehydrogenation pathway.

Chemodivergent Dehydrogenative Coupling of Alcohols by 3d Metal Catalysts

AbstractChemodivergent synthesis by transition metal catalysts is a straightforward and sustainable approach to achieving valuable organic compounds. Especially, the chemodivergent dehydrogenative couplings of alcohols with organic motifs to develop various saturated and unsaturated compounds are highly environmentally benign due to the reduced waste generation. In this concept review, we presented the 3d transition metal (Mn, Fe, Co, and Ni)‐catalyzed chemodivergent synthesis of imines and amines, saturated and unsaturated carbonyl/alcohol compounds, saturated and unsaturated nitriles, N‐heterocycles, and N‐/C‐alkylated indoles. The discussed reaction commanded two or three different products with high chemoselectivity by changing specific reaction parameters, but keeping the catalyst unchanged. Generally, the acceptorless dehydrogenative coupling (ADC) provides unsaturated moieties, whereas the borrowing‐hydrogen (BH) process results in saturated compounds.

Nickel Pincer Complexes Catalyzed Sustainable Synthesis of 3,4-Dihydro-2H-1,2,4-benzothiadiazine-1,1-dioxides via Acceptorless Dehydrogenative Coupling of Primary Alcohols.

We report the atom-economic and sustainable synthesis of biologically important 3,4-dihydro-2H-1,2,4-benzothiadiazine-1,1-dioxide (DHBD) derivatives from readily available aromatic primary alcohols and 2-aminobenzenesulfonamide catalyzed by nickel(II)-N∧N∧S pincer-type complexes. The synthesized nickel complexes have been well-studied by elemental and spectroscopic (FT-IR, NMR, and HRMS) analyses. The solid-state molecular structure of complex 2 has been authenticated by a single-crystal X-ray diffraction study. Furthermore, a series of 3,4-dihydro-2H-1,2,4-benzothiadiazine-1,1-dioxide derivatives have been synthesized (24 examples) utilizing a 3 mol % Ni(II) catalyst through acceptorless dehydrogenative coupling of benzyl alcohols with benzenesulfonamide. Gratifyingly, the catalytic protocol is highly selective with the yield up to 93% and produces eco-friendly water/hydrogen gas as byproducts. The control experiments and plausible mechanistic investigations indicate that the coupling of the in situ generated aldehyde with benzenesulfonamide leads to the desired product. In addition, a large-scale synthesis of one of the thiadiazine derivatives unveils the synthetic usefulness of the current methodology.

Facile Synthesis of 2-Substituted Quinazolines via Ruthenium(II)-Catalyzed Acceptorless Dehydrogenative Coupling

Abstract:: This study aims to develop a practical and facile one-pot synthesis of 2- substituted quinazolines. Using a commercially available and structurally simple ruthenium( II) complex as the catalyst to synthesize a series of quinazoline derivatives via acceptorless dehydrogenative coupling. The mechanism of this reaction was explored by control reaction and DFT calculation. This protocol offers access to a diverse array of quinazoline derivatives (52 examples) in moderate to excellent yields (29%-98%). In summary, we have developed an efficient one-pot ruthenium (II)-catalyzed ADC synthesis of quinazoline under an air atmosphere. The reaction only produces hydrogen and water as by-products, serving as a sustainable and atom-efficient synthetic approach.

Nickel-Catalyzed Chemodivergent Coupling of Alcohols: Efficient Routes to Access α,α-Disubstituted Ketones and α-Substituted Chalcones.

Chemodivergent (de)hydrogenative coupling of primary and secondary alcohols is achieved utilizing an inexpensive nickel catalyst, (6-OH-bpy)NiCl2 . This protocol demonstrates the synthesis of branched carbonyl compounds, α,α-disubstituted ketones, and α-substituted chalcones via borrowing hydrogen strategy and acceptorless dehydrogenative coupling, respectively. A wide range of aryl-based secondary alcohols are coupled with various primary alcohols in this tandem dehydrogenation/hydrogenation reaction. The nickel catalyst, along with KOt Bu or K2 CO3 , governed the selectivity for the formation of branched saturated ketones or chalcones. A preliminary mechanistic investigation confirms the reversible dehydrogenation of alcohols to carbonyls via metal-ligand cooperation (MLC) and the involvement of radical intermediates during the reaction.

Formation of ylidenehydrazines enabled by manganese-catalyzed acceptorless dehydrogenative coupling

A practical one-pot Mn-catalyzed tandem dehydrogenative condensation coupling of alcohols with hydrazines and halides to form ylidenehydrazines via an acceptorless dehydrogenative coupling strategy is reported.

Cp*Ir(III) complexes catalyzed solvent-free synthesis of quinolines, pyrroles and pyridines via an ADC strategy.

A trio of Ir(III) complexes that are held together by a picolinamidato moiety were created. In our earlier research, we demonstrated the catalytic activity of the complexes for producing alpha-alkylated ketones from a ketone or secondary alcohol with a primary alcohol in the presence of a catalytic amount of a Cp*Ir(III) catalyst and tBuOK in toluene at 110 °C using the hydrogen-borrowing technique. Earlier many research groups had synthesized quinoline, pyrrole, and pyridine derivatives using 2-amino alcohol and ketone or secondary alcohol derivatives as starting materials, but in all those cases the reaction conditions are not suitable in terms of green synthesis like more catalyst loading, base loading, long reaction time, and high temperature. In addition, most of the reactions contain phosphine a hazardous by-product, along with the catalyst. Keeping in mind these shortcomings, we tried to expand the use of our catalysts after achieving an excellent result in our previous work, and we were successful in producing quinoline, pyrrole, and pyridine derivatives through acceptor-less dehydrogenative coupling (ADC) procedures at 90-110 °C under neat/solvent-free conditions and achieved good to exceptional yields of those nitrogen-containing heterocycles. This methodology is attractive because it is environmentally benign and allows for the "green" synthesis of nitrogen-containing heterocycles. All that is required is a modest quantity of catalyst and base, and the by-products are merely H2O and H2.

An NNN Pd(II) pincer complex with 1,1-diaminoazine: a versatile catalyst for acceptorless dehydrogenative coupling reactions.

An azine-based, non-palindromic, neutral NNN-pincer ligand was synthesised in a single step with an yield of 85%. The palladation of the ligand, using Pd(OAc)2, was performed in acetonitrile at room temperature to obtain the pincer complex in 88% yield through a simple, cost-effective, and straightforward synthetic procedure. The structure of the complex was confirmed by 1H NMR, 13C NMR, FT-IR, and mass spectrometry. The variable temperature NMR spectra revealed the stability of the complex even at higher temperatures, a characteristic feature of pincer complexes. The generated complex proved to be a versatile catalyst for Acceptorless Dehydrogenative Coupling (ADC) to synthesize N-heterocycles: (i) 1,2-disubstituted benzimidazoles, (ii) 2-phenylquinolines, (iii) 2-phenylquinoxalines and (iv) 2-phenylquinazolinones. Since the side products of the reactions are H2O and H2 gas, the catalysis can be considered as a green catalytic process. Quantum chemical calculations indicated the participation of a possible nitrene-imide conversion process during the Metal-Ligand Cooperation (MLC) in ADC reactions.

Potent pincer-zinc catalyzed homogeneous α-alkylation and Friedländer quinoline synthesis reaction of secondary alcohols/ketones with primary alcohols.

Herein, we describe an air- and moisture-stable, homogeneous zinc catalyst stabilised using an electron deficient N^N^N pincer-type ligand. This ternary, penta-coordinated neutral molecular catalyst [Zn(N^N^N)Cl2] selectively produces α-alkylated ketone derivatives (14 examples) through a one-pot acceptorless dehydrogenative coupling (ADC) reaction between secondary and primary alcohols using the borrowing hydrogen (BH) approach in good to excellent isolated yields (up to 93%). It is worth noting that this catalyst also provides an eco-friendly route for the synthesis of quinoline derivatives (30 examples) using 2-aminobenzyl alcohols as alkylating agents via successive dehydrogenative coupling and N-annulation reactions. This cost effective, easy to synthesize and environmentally benign catalyst shows excellent stability in catalytic cycles under open-air conditions, as evident from its high turnover number (∼104), and is activated by using a catalytic amount of base under milder conditions.