62056-12-6

Upstream product

• 459-56-3 4-fluorobenzylic alcohol 
• 98-86-2 acetophenone 
• 98-85-1 1-Phenylethanol 

Relevant academic research and scientific papers

Bifunctional RuII-Complex-Catalysed Tandem C?C Bond Formation: Efficient and Atom Economical Strategy for the Utilisation of Alcohols as Alkylating Agents

Catalytic activities of a series of functional bipyridine-based RuIIcomplexes in β-alkylation of secondary alcohols using primary alcohols were investigated. Bifunctional RuIIcomplex (3 a) bearing 6,6’-dihydroxy-2,2’-bipyridine (6DHBP) ligand exhibited the highest catalytic activity for this reaction. Using significantly lower catalyst loading (0.1 mol %) dehydrogenative carbon?carbon bond formation between numerous aromatic, aliphatic and heteroatom substituted alcohols were achieved with high selectivity. Notably, for the synthesis of β-alkylated secondary alcohols this protocol is a rare one-pot strategy using a metal–ligand cooperative RuIIsystem. Remarkably, complex 3 a demonstrated the highest reactivity compared to all the reported transition metal complexes in this reaction.

Electronically tuneable orthometalated RuII–NHC complexes as efficient catalysts for C–C and C–N bond formations via borrowing hydrogen strategy

The catalytic activities of a series of simple and electronically tuneable cyclometalated RuII–NHC complexes (2a–d) were explored in various C–C/N bond formations following the borrowing hydrogen process. Slight modifications in the ligand backbone were noted to tune the activities of these complexes. Among them, the complex 2d featuring a 1,2,4-triazolylidene donor with a 4-NO2–phenyl substituent displayed the highest activity for the coupling of diverse secondary and primary alcohols with a low catalyst loading of 0.01 mol% and a sub-stoichiometric amount of inexpensive KOH base. The efficacy of this simple system was further showcased in the challenging one-pot unsymmetrical double alkylation of secondary alcohols using different primary alcohols. Moreover, the complex 2d also effectively catalyses the selective mono-N-methylation of various aromatic and aliphatic primary amines using methanol to deliver a range of N-methyl amines. Mechanistically, the β-alkylation reaction follows a borrowing hydrogen pathway which was established by the deuterium labelling experiment in combination with various control experiments. Intriguingly, in situ1H NMR and ESI-MS analyses evidently suggested the involvement of a Ru–H species in the catalytic cycle and further, the kinetic studies revealed a first order dependence of the reaction rate on the catalyst as well as the alcohol concentrations.

Selective C-alkylation Between Alcohols Catalyzed by N-Heterocyclic Carbene Molybdenum

The first implementation of a molybdenum complex with an easily accessible bis-N-heterocyclic carbene ligand to catalyze β-alkylation of secondary alcohols via borrowing-hydrogen (BH) strategy using alcohols as alkylating agents is reported. Remarkably high activity, excellent selectivity, and broad substrate scope compatibility with advantages of catalyst usage low to 0.5 mol%, a catalytic amount of NaOH as the base, and H2O as the by-product are demonstrated in this green and step-economical protocol. Mechanistic studies indicate a plausible outer-sphere mechanism in which the alcohol dehydrogenation is the rate-determining step.

Switchable β-alkylation of secondary alcohols with primary alcohols by a well-defined cobalt catalyst

β-alkylation of secondary alcohols with primary alcohols to selectively generate alcohols by a well-defined Co catalyst is presented. Remarkably, a low catalyst loading of 0.7 mol % can be employed for the reaction. More significantly, this study represents the first Co-catalyzed switchable alcohol/ketone synthesis by simply manipulating the reaction parameters. In addition, the transformation is environmentally friendly, with water as the only byproduct.

Pincer-Nickel Catalyzed Selective Guerbet-Type Reactions

We report here the synthesis and characterization of a series of NNN pincer-nickel complexes of the type (R2NNN)NiCl2(CH3CN) (R = iPr, tBu, Cy, Ph, and p-F-C6H4) based on bis(imino)pyridine ligands. In solution, these complexes are found to be equilibrium mixtures containing one and two pincer ligands, respectively. While the crystal structure of the former was reported by us recently for R = iPr, we report the crystal structure of the latter in this study for R = p-F-C6H4. The considered NNN pincer-Ni complexes have been successfully employed to accomplish the catalytic β-alkylation of several secondary alcohols with a variety of benzyl alcohols at 140 °C with high yields and unprecedented turnovers. A maximum of 92% yield of the β-alkylated product at 18 ?400 TON was obtained in the reaction of benzyl alcohol with 1-(4-(trifluoromethyl)phenyl)ethane-1-ol in the presence of 0.005 mol % of (Ph2NNN)NiCl2(CH3CN) and 5 mol % of NaOtBu at 140 °C after 24 h. The reaction exhibits zero-order dependence of rate on catalyst concentration and first-order dependence on the concentration of base, benzyl alcohol, and 1-phenyl ethanol which points to the base-mediated aldol condensation as the rate-determining step. Most of the intermediates involved in catalysis have been identified by HRMS. To the best of our knowledge, this is the first report on a pincer-Ni catalyzed β-alkylation of alcohols and, hitherto, such unprecedented turnovers have not been reported with a homogeneous molecular nickel-based catalyst.

A Proton-Responsive Pyridyl(benzamide)-Functionalized NHC Ligand on Ir Complex for Alkylation of Ketones and Secondary Alcohols

A Cp*Ir(III) complex (1) of a newly designed ligand L1 featuring a proton-responsive pyridyl(benzamide) appended on N-heterocyclic carbene (NHC) has been synthesized. The molecular structure of 1 reveals a dearomatized form of the ligand. The protonation of 1 with HBF4 in tetrahydrofuran gives the corresponding aromatized complex [Cp*Ir(L1H)Cl]BF4 (2). Both compounds are characterized spectroscopically and by X-ray crystallography. The protonation of 1 with acid is examined by 1H NMR and UV-vis spectra. The proton-responsive character of 1 is exploited for catalyzing α-alkylation of ketones and β-alkylation of secondary alcohols using primary alcohols as alkylating agents through hydrogen-borrowing methodology. Compound 1 is an effective catalyst for these reactions and exhibits a superior activity in comparison to a structurally similar iridium complex [Cp*Ir(L2)Cl]PF6 (3) lacking a proton-responsive pendant amide moiety. The catalytic alkylation is characterized by a wide substrate scope, low catalyst and base loadings, and a short reaction time. The catalytic efficacy of 1 is also demonstrated for the syntheses of quinoline and lactone derivatives via acceptorless dehydrogenation, and selective alkylation of two steroids, pregnenolone and testosterone. Detailed mechanistic investigations and DFT calculations substantiate the role of the proton-responsive ligand in the hydrogen-borrowing process.

Phosphine-free pincer-ruthenium catalyzed biofuel production: High rates, yields and turnovers of solventless alcohol alkylation

Phosphine-free pincer-ruthenium carbonyl complexes based on bis(imino)pyridine and 2,6-bis(benzimidazole-2-yl) pyridine ligands have been synthesized. For the β-alkylation of 1-phenyl ethanol with benzyl alcohol at 140 °C under solvent-free conditions, (Cy2NNN)RuCl2(CO) (0.00025 mol%) in combination with NaOH (2.5 mol%) was highly efficient (ca. 93% yield, 372?000 TON at 12?000 TO h-1). These are the highest reported values hitherto for a ruthenium based catalyst. The β-alkylation of various alcohol combinations was accomplished with ease which culminated to give 380?000 TON at 19?000 TO h-1 for the β-alkylation of 1-phenyl ethanol with 3-methoxy benzyl alcohol. DFT studies were complementary to mechanistic studies and indicate the β-hydride elimination step involving the extrusion of acetophenone to be the overall RDS. While the hydrogenation step is favored for the formation of α-alkylated ketone, the alcoholysis step is preferred for the formation of β-alkylated alcohol. The studies were extended for the upgradation of ethanol to biofuels. Among the pincer-ruthenium complexes based on bis(imino)pyridine, (Cy2NNN)RuCl2(CO) provided high productivity (335 TON at 170 TO h-1). Sterically more open pincer-ruthenium complexes such as (Bim2NNN)RuCl2(CO) based on the 2,6-bis(benzimidazole-2-yl) pyridine ligand demonstrated better reactivity and gave not only good ethanol conversion (ca. 58%) but also high turnovers (ca. 2100) with a good rate (ca. 710 TO h-1). Kinetic studies indicate first order dependence on concentration of both the catalyst and ethanol. Phosphine-free catalytic systems operating with unprecedented activity at a very low base loading to couple lower alcohols to higher alcohols of fuel and pharmaceutical importance are the salient features of this report. This journal is

Reaction condition controlled nickel(ii)-catalyzed C-C cross-coupling of alcohols

The challenge in the C-C cross-coupling of secondary and primary alcohols using acceptorless dehydrogenation coupling (ADC) is the difficulty in accurately controlling product selectivities. Herein, we report a controlled approach to a diverse range of β-alkylated secondary alcohols, α-alkylated ketones and α,β-unsaturated ketones using the ADC methodology employing a Ni(ii) 4,6-dimethylpyrimidine-2-thiolate cluster catalyst under different reaction conditions. This catalyst could tolerate a wide range of substrates and exhibited a high activity for the annulation reaction of secondary alcohols with 2-aminobenzyl alcohols to yield quinolines. This work is an example of precise chemoselectivity control by careful choice of reaction conditions.

C-Alkylation of Secondary Alcohols by Primary Alcohols through Manganese-Catalyzed Double Hydrogen Autotransfer

A new Mn-catalyzed alkylation of secondary alcohols with non-activated alcohols is presented. The use of a stable and well-defined manganese pincer complex, stabilized by a PNN ligand, together with a catalytic amount of base enabled the conversion of renewable alcohol feedstocks to a broad range of higher-value alcohols in good yields with water as the sole byproduct. The strategy eliminates the need for exogenous and detrimental alkyl halides as well as the use of noble metal catalysts, making the C-alkylation through double hydrogen autotransfer a highly sustainable and environmentally benign process. Mechanistic investigations support a hydrogen autotransfer mechanism in which a non-innocent ligand plays a crucial role.

Ruthenium-Catalyzed β-Alkylation of Secondary Alcohols and α-Alkylation of Ketones via Borrowing Hydrogen: Dramatic Influence of the Pendant N-Heterocycle

Three bidentate ruthenium(II) complexes with a pyridonate fragment were prepared and fully characterized. These complexes are structurally similar, but differ in their pendant substituents. Complex 1 contains a phenyl unit, whereas complexes 2 and 3 have uncoordinated thienyl and thiazolyl groups, respectively. These complexes were tested as catalysts for β-alkylation of secondary alcohols with primary alcohols, and 3 shows the highest activity, suggesting the thiazolyl ring participates in the catalytic process. Furthermore, 3 is an excellent catalyst for α-alkylation of ketones with primary alcohols. Various α-alkylated ketones were synthesized in high yields, by using 0.05 mol % 3 and 0.25 equiv of t-BuOK within 30 min.