Primary Benzylic Alcohols Research Articles

Microwave assisted synthesis of ErxYbyCa1-x-yMoO4 nano-phosphor for efficient temperature sensing and catalytic applications

Here, Er/Yb Co-doped CaMoO4 materials (ErxYbyCa1−x−yMoO4 NPs where x = 0, 0.01 and y = 0, 0.05, 0.10, 0.15, 0.20) were prepared by microwave-assisted method and its pure-tetragonal structure were confirmed by X-ray diffraction spectra (XRD), Rietveld-refinement and Raman-vibrational spectra. The transmission-electron microscopy (TEM) study indicates the formation of nearly spherical shaped nanomaterial with average size of ~ 15 nm. Additionally, absorption and emission properties were studied by UV–Visible–NIR and photoluminescence (PL) spectrometer. The UV–Visible–NIR spectra attribute absorption of Er3+ ion in visible region (380–700 nm) and absorption of Yb3+ ion in near-infrared region (700–1400 nm). Moreover, PL up-conversion spectra of the sample recorded under excitation wavelength 980 nm. The PL peaks were observed at 530, 544–552, and 656–670 nm. Prominent PL-intensity was observed for Er0.01Yb0.15Ca0.84MoO4 phosphor. Temperature dependent PL study reveals that present phosphor is robust phosphor for temperature sensor. In addition, Er3+/Yb3+ doped CaMoO4 nanomaterials exhibited excellent activity and selectivity in the aerial oxidation of benzoin over benzyl under oxidant-free reaction conditions. The synergistic effect Er3+/Yb3+ co-doing in CaMoO4 matrix was observed, where only CaMoO4 material found to be inactive towards above oxidation reaction. Moreover, the oxidation of primary benzyl-alcohols was furnished in presence of tertiary butyl hydroperoxideas oxidant.

Catalytic dehydrative cross-coupling of alcohols: An eco-friendly approach to unsymmetrical ethers

Developing green as well as sustainable protocols by employing cheap and readily available catalysts and/or reagents without using environmentally hazardous solvents is becoming more significant to the researcher community. Here, we introduce a green and metal-free catalytic method for the etherification of alcohols by using catalytic NH4I and oxone under mild conditions. The reagents we employed are inexpensive, abundant in nature, readily available, easy to handle and produce non-polluting by-products, which can be easily removable by simple aqueous work-up. This makes our approach more convenient, sustainable and economically viable. The present catalytic system does not require any organic solvent as reaction medium to facilitate the reaction. Using this green approach, we have synthesized a wide range of unsymmetrical ethers from two distinct types of alcohols (secondary benzylic and primary (benzylic or non-benzylic) alcohols) which demonstrated the efficiency of our protocol. Further, the gram scale reactions established the feasibility in scaling-up of our process.

Selective N-functionalization of Arylhydrazines with Primary Alcohols and Acids under PPh3/DDQ System.

We present a PPh3/DDQ-mediated regiospecific selective N-functionalization of arylhydrazines with primary benzylic alcohols and aryl carboxylic acids for the synthesis of N1-benzyl arylhydrazines and N2-acyl arylhydrazines, respectively. This metal- and base-free approach features very short reaction times (about 10 min), broad substrate scope, good functional group tolerance, and mild reaction conditions. Furthermore, N1-benzlated products have also been successfully applied to the concise synthesis of N-substituted indoles and anticancer drug MDM2 inhibitor.

Hydrogen-Induced Formation of Surface Acid Sites on Pt/Al(PO3)3 Enables Remarkably Efficient Hydrogenolysis of C-O Bonds in Alcohols and Ethers.

The hydrogenolysis of oxygenates such as alcohols and ethers is central to the biomass valorization and also a valuable transformation in organic synthesis. However, a mild and efficient catalyst system for the hydrogenolysis of a large variety of alcohols and ethers with various functional groups is still underdeveloped. Here, we report an aluminum metaphosphate-supported Pt nanoparticles (Pt/Al(PO3)3) for the hydrogenolysis of a wide variety of primary, secondary, and tertiary alkyl and benzylic alcohols, and dialkyl, aryl alkyl, and diaryl ethers, including biomass-derived furanic compounds, under mild conditions (0.1-1 atm of H2, as low as 70 °C). Mechanistic studies suggested that H2 induces formation of the surface Brønsted acid sites via its cleavage by supported Pt nanoparticles. Accordingly, the high efficiency and the wide applicability of the catalyst system are attributed to the activation and cleavage of C-O bonds by the hydrogen-induced Brønsted acid sites with the assistance of Lewis acidic Al sites on the catalyst surface. The high efficiency of the catalyst implies its potential application in energy-efficient biomass valorization or fine chemical synthesis.

Hydrogen‐Induced Formation of Surface Acid Sites on Pt/Al(PO3)3 Enables Remarkably Efficient Hydrogenolysis of C−O Bonds in Alcohols and Ethers

AbstractThe hydrogenolysis of oxygenates such as alcohols and ethers is central to the biomass valorization and also a valuable transformation in organic synthesis. However, a mild and efficient catalyst system for the hydrogenolysis of a large variety of alcohols and ethers with various functional groups is still underdeveloped. Here, we report an aluminum metaphosphate‐supported Pt nanoparticles (Pt/Al(PO3)3) for the hydrogenolysis of a wide variety of primary, secondary, and tertiary alkyl and benzylic alcohols, and dialkyl, aryl alkyl, and diaryl ethers, including biomass‐derived furanic compounds, under mild conditions (0.1–1 atm of H2, as low as 70 °C). Mechanistic studies suggested that H2 induces formation of the surface Brønsted acid sites via its cleavage by supported Pt nanoparticles. Accordingly, the high efficiency and the wide applicability of the catalyst system are attributed to the activation and cleavage of C−O bonds by the hydrogen‐induced Brønsted acid sites with the assistance of Lewis acidic Al sites on the catalyst surface. The high efficiency of the catalyst implies its potential application in energy‐efficient biomass valorization or fine chemical synthesis.

Photochemical Hydrogen Atom Transfer Catalysis for Dehydrogenation of Alcohols To Form Carbonyls.

Controllable oxidation of alcohols to carbonyls is one of the fundamental transformations in organic chemistry. Herein, we report an unprecedented visible-light-mediated metal-free oxidation of alcohols to carbonyls with hydrogen evolution. By synergistic combination of organophotocatalyst 4CzIPN and a thiol hydrogen atom transfer catalyst, a broad range of alcohols, including primary and secondary benzylic alcohols as well as aliphatic alcohols, were readily oxidized to carbonyls in moderate to excellent yields. A site-selective oxidation has also been achieved by this protocol. Mechanistic investigation indicates that the oxidation proceeds through an oxidative radical-polar crossover process to obtain an α-oxy carbon cation.

Borrowing hydrogen and dehydrogenative/oxidative cyclization reactions catalyzed by a CCC-NHC pincer Re complex: An air stable catalyst for the synthesis of α-alkylated ketones and quinolines

Successful catalytic activity of the CCC-NHC pincer Re(I) complex was achieved for the borrowing hydrogen coupling reaction between primary and secondary benzylic alcohols. An expansive scope of 17 aromatic and 2 aliphatic substrates were investigated and isolated yields from 40% to 91% were collected. The aliphatic substrates yielded complex aldol self-condensation by-products. The catalytic activity of the CCC-NHC pincer Re(I) complex was also evaluated for the formation of quinolines via the dehydrogenative/oxidative cyclization of 2-aminobenzyl alcohols with benzylic ketones or secondary benzylic alcohols. Isolated yields from 68% to 87% were obtained for 12 examples. All products and by-products were fully characterized by 1H &13C NMR and mass spectroscopies. Control studies such as dehydrogenative and hydrogen transfer reaction were carried out, and the results from these experiments supported a proposed mechanism of a borrowing hydrogen coupling reaction catalyzed by the CCC-NHC pincer Re(I) complex.

Copper Pyrithione (CuPT)-Catalyzed Oxidation of Secondary and Primary Benzyl Alcohols with Molecular oxygen or Air Under Mild Conditions

Copper Pyrithione (CuPT)-Catalyzed Oxidation of Secondary and Primary Benzyl Alcohols with Molecular oxygen or Air Under Mild Conditions

Catalytic Oxidative Cleavage of C(OH)-C Bonds in Lignin Model Compounds to Carboxylic Acids by Fe(NO3)3.9H2O/NaI/DMSO.

The secondary C(OH)-C bonds are abundant in biomass such as lignin and cellulose. Thus, selective cleavage of the C(OH)-C bonds into value chemicals attracted much attention. Molecular iodine has received considerable attention as an inexpensive and readily available catalyst to yield the corresponding products in excellent yields with high selectivity, but it is highly corrosive and toxic, making its use somewhat unattractive. In this study, I2 was generated in situ from Fe(NO3)3.9H2O/NaI, which was further combined with Fe(NO3)3.9H2O to catalyze the oxidation process. In the reaction, the H2O molecule from the reaction and Fe(NO3)3.9H2O attacked the phenylglyoxal to form benzaldehyde, which was further oxidized to benzoic acid. Aryl primary and secondary benzylic alcohols from lignin were successfully transformed into aryl carboxylic acids by Fe(NO3)3.9H2O/NaI/DMSO. The catalytic system was green and efficient, avoiding the usage of toxic and corrosive molecular I2. From the experiments, it was clear that the yield of the product from the substrates with an electron-donating group was higher than that of electron-withdrawing substituted substrates, which was similar to the aryl secondary alcohols. Aryl alkyl ketones were also successfully conducted by the Fe(NO3)3.9H2O/NaI/DMSO catalytic system.

Selective oxidation of primary benzylic alcohols to aldehydes using NaNO3 under ball milling

A facile method for oxidation of primary benzylic alcohols to the corresponding aldehydes is reported using NaNO3/P2O5 under high-speed ball-milling conditions. This approach is clean, efficient, and exhibits broad functional group compatibility.

Selective visible-light-induced photooxidation of benzylic alcohols to corresponding carbonyl compounds over titanium dioxide: A study of the structure-reactivity relationship

We herein report the selective photooxidation of primary and secondary benzylic alcohol to the corresponding carbonyl compounds over titanium dioxide in acetonitrile under visible light irradiation. To enhance the understanding in which way parameters influence the reaction rate, several factors, such as initial concentration, catalyst amount, light intensity, and its spectral characteristics were investigated. The use of titanium dioxide in anatase modification as a photocatalyst was also considered with a significant change in the reaction rate. Further studies on benzylic alcohols substituted with different electron-donating (EDG) and electron-withdrawing groups (EWG) showed that the Hammett plot provided an excellent structure-reactivity relationship between substitution and rate constant for primary substituted alcohols. It displayed an upward curvature indicating that the reaction mechanism changed as the substituents became more electron-withdrawing. The kinetic isotope effect (KIE) revealed that the α-H abstraction was the rate-determining step for benzylic alcohols substituted with EDGs. When comparing the reaction rate between primary and secondary benzylic alcohols, it was found that the rate of reaction for secondary benzylic alcohols bearing EDGs decreased compared to primary benzylic alcohols, an increase was observed when the aromatic ring was substituted with EWGs.

Boryl Radical Activation of Benzylic C-OH Bond: Cross-Electrophile Coupling of Free Alcohols and CO2 via Photoredox Catalysis.

A new strategy for the direct cleavage of the C(sp3)-OH bond has been developed via activation of free alcohols with neutral diphenyl boryl radical generated from sodium tetraphenylborate under mild visible light photoredox conditions. This strategy has been verified by cross-electrophile coupling of free alcohols and carbon dioxide for the synthesis of carboxylic acids. Direct transformation of a range of primary, secondary, and tertiary benzyl alcohols to acids has been achieved. Control experiments and computational studies indicate that activation of alcohols with neutral boryl radical undergoes homolysis of the C(sp3)-OH bond, generating alkyl radicals. After reducing the alkyl radical into carbon anion under photoredox conditions, the following carboxylation with CO2 affords the coupling product.

Molecular Iodine Mediated Synthesis of 2,4,5-Trisubstituted Imidazoles Commencing from α-Methylene Ketones and Benzylic Primary Alcohols Using a One-Pot, Two-Step Approach

Molecular Iodine Mediated Synthesis of 2,4,5-Trisubstituted Imidazoles Commencing from α-Methylene Ketones and Benzylic Primary Alcohols Using a One-Pot, Two-Step Approach

Four- and five-coordinate nickel(ii) complexes bearing new diphosphine-phosphonite and triphosphine-phosphite ligands: catalysts for N-alkylation of amines.

The reaction of Ph2PCH2OH with PhPCl2 and PCl3 in the presence of Et3N afforded new phosphonite compounds PhP(OCH2PPh2)21 and P(OCH2PPh2)32, respectively. The reaction between 1 and [NiCl2(DME)] in dichloromethane gave the five-coordinate complex [NiCl2(1-κ3P,P,P)] 3. Conversely, 1 reacts with [NiCl2(DME)] in the presence of NH4PF6 in dichloromethane to yield the four coordinate ionic complex [NiCl(1-κ3P,P,P)][PF6] 4. The reactions between 1, [NiCl2(DME)] and KPF6 in the presence of RNC (R = Xylyl, tBu and iPr) in dichloromethane yielded the five coordinate monocationic [NiCl(1-κ3P,P,P)(RNC)][PF6] (R = Xylyl) and dicationic [Ni(1-κ3P,P,P)(RNC)2][PF6]2 (R = tBu and iPr) complexes, respectively. The analogous reaction of 2 with [NiCl2(DME)] in the presence of KPF6 gave complex [NiCl(2-κ4P,P,P,P)][PF6], 8. The structures of all complexes were determined by single crystal X-ray diffraction studies and supported by spectroscopic methods. To demonstrate their catalytic application, N-alkylation reactions between primary aryl amines, benzyl and 4-methoxy benzyl alcohols were found to proceed smoothly in the presence of 2.5 mol% of complexes bearing ligand 1 and <0.5 mmol of KOBut in toluene at 140 °C. The C–N coupled products were formed in very good yields. Its substrate scope includes sterically encumbered, heterocyclic amines and aliphatic alcohol.

Characterization of a thermotolerant aryl-alcohol oxidase from Moesziomyces antarcticus oxidizing 5-hydroxymethyl-2-furancarboxylic acid

The development of enzymatic processes for the environmentally friendly production of 2,5-furandicarboxylic acid (FDCA), a renewable precursor for bioplastics, from 5-hydroxymethylfurfural (HMF) has gained increasing attention over the last years. Aryl-alcohol oxidases (AAOs) catalyze the oxidation of HMF to 5-formyl-2-furancarboxylic acid (FFCA) through 2,5-diformylfuran (DFF) and have thus been applied in enzymatic reaction cascades for the production of FDCA. AAOs are flavoproteins that oxidize a broad range of benzylic and aliphatic allylic primary alcohols to the corresponding aldehydes, and in some cases further to acids, while reducing molecular oxygen to hydrogen peroxide. These promising biocatalysts can also be used for the synthesis of flavors, fragrances, and chemical building blocks, but their industrial applicability suffers from low production yield in natural and heterologous hosts. Here we report on heterologous expression of a new aryl-alcohol oxidase, MaAAO, from Moesziomyces antarcticus at high yields in the methylotrophic yeast Pichia pastoris (recently reclassified as Komagataella phaffii). Fed-batch fermentation of recombinant P. pastoris yielded around 750 mg of active enzyme per liter of culture. Purified MaAAO was highly stable at pH 2–9 and exhibited high thermal stability with almost 95% residual activity after 48 h at 57.5 °C. MaAAO accepts a broad range of benzylic primary alcohols, aliphatic allylic alcohols, and furan derivatives like HMF as substrates and some oxidation products thereof like piperonal or perillaldehyde serve as building blocks for pharmaceuticals or show health-promoting effects. Besides this, MaAAO oxidized 5-hydroxymethyl-2-furancarboxylic acid (HMFCA) to FFCA, which has not been shown for any other AAO so far. Combining MaAAO with an unspecific peroxygenase oxidizing HMFCA to FFCA in one pot resulted in complete conversion of HMF to FDCA within 144 h. MaAAO is thus a promising biocatalyst for the production of precursors for bioplastics and bioactive compounds.Key points• MaAAO from M. antarcticus was expressed in P. pastoris at 750 mg/l.• MaAAO oxidized 5-hydroxymethyl-2-furancarboxylic acid (HMFCA).• Complete conversion of HMF to 2,5-furandicarboxylic acid by combining MaAAO and UPO.

Cerium-photocatalyzed aerobic oxidation of benzylic alcohols to aldehydes and ketones.

We have developed a cerium-photocatalyzed aerobic oxidation of primary and secondary benzylic alcohols to aldehydes and ketones using inexpensive CeCl3·7H2O as photocatalyst and air oxygen as the terminal oxidant.

Chemically functionalized MIL-101-NH2 with cobalt(II) tetrasulfophthalocyanine: an efficient catalyst for the aerobic oxidation of alcohols and one-pot tandem conversion of alcohols to propargylamines

In this investigation, MIL-101-NH2 chemically functionalized with cobalt(II) tetrasulfophthalocyanine (CoTSPc) through a superior electrostatic interaction reaction. The configuration of the synthesized composite was characterized using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), thermal gravimetric analysis (TGA), energy-dispersive X-ray spectroscopy (EDS), scanning electron microscope (SEM), and inductively coupled plasma optical emission spectrometer (ICP-OES). This spongy composite showed excellent catalytic activity in the aerobic oxidation reaction of primary and secondary benzylic alcohols. The generated catalyst's behavior was examined to synthesize propargylamines via tandem oxidative A3 coupling process to illustrate the maximum potential of the synthesized catalyst. Utilizing air as an oxidant, operational simplicity, easy preparation, apt yielding, non‐hazardous nature of the catalyst, and reusability are the essential advantages of this catalyst.

Rapid Multialkylation of Aqueous Ammonia with Alcohols by Heterogeneous Iridium Catalyst under Simple Conditions

AbstractThis paper reports the synthesis of tertiary and secondary amines from aqueous ammonia and benzylic alcohols by titania‐supported iridium catalyst. It is a successful example of heterogeneous systems at moderate temperature without either additional solvent or high pressure. The catalytic system showed good tolerance to the atmosphere condition and performed rapidly to give tribenzylamine a yield of over 99 % within 6 hours in argon. The crystal structure of titania supports for iridium catalysts strongly affected their activity. The catalysis smoothly proceeded on larger scales. The catalyst could be easily reused and run at least for 5 cycles without significant loss of activity. The highly‐dispersed iridium species of less than 2 nm in diameter would be responsible for the excellent catalytic activity. This catalyst is well applicable in multialkylation of aqueous ammonia with various primary and secondary benzylic alcohols.

Enantioselective α-Arylation of Primary Alcohols under Sequential One-Pot Catalysis

Secondary benzylic alcohols and diarylmethanols are common structural motifs of biologically active and medicinally relevant compounds. Here we report their enantioselective synthesis by α-arylation of primary aliphatic and benzylic alcohols under sequential catalysis integrating a Ru-catalyzed hydrogen transfer oxidation and a Ru-catalyzed nucleophilic addition. The method can be applied to various alcohols and aryl nucleophiles tolerating a range of functional groups, including secondary alcohols, ketones, alkenes, esters, NH amides, tertiary amines, aryl halides, and heterocycles.

Oxalohydrazide Ligands for Copper‐Catalyzed C−O Coupling Reactions with High Turnover Numbers

AbstractHere, we report a class of ligands based on oxalohydrazide cores and N‐amino pyrrole and N‐amino indole units that generates long‐lived copper catalysts for couplings that form the C−O bonds in biaryl ethers. These Cu‐catalyzed coupling of phenols with aryl bromides occurred with turnovers up to 8000, a value which is nearly two orders of magnitude higher than those of prior couplings to form biaryl ethers and nearly an order of magnitude higher than those of any prior copper‐catalyzed coupling of aryl bromides and chlorides. This ligand also led to copper systems that catalyze the coupling of aryl chlorides with phenols and the coupling of aryl bromides and iodides with primary benzylic and aliphatic alcohols. A wide variety of functional groups including nitriles, halides, ethers, ketones, amines, esters, amides, vinylarenes, alcohols and boronic acid esters were tolerated, and reactions occurred with aryl bromides in pharmaceutically related structures.