Secondary Alcohols Research Articles

Kinetic Studies of the Oxidation of Primary Acyclic and Secondary Cyclic Perfumery alcohols using N- Bromosuccinimide in Alkaline Medium

Kinetic Studies of the Oxidation of Primary Acyclic and Secondary Cyclic Perfumery alcohols using N- Bromosuccinimide in Alkaline Medium

Oxidation of Primary Alcohols and Aldehydes to Carboxylic Acids with 1-Hydroxycyclohexyl Phenyl Ketone.

The oxidation of primary alcohols to the corresponding carboxylic acids is one of the fundamental and useful reactions in organic synthesis. In this paper, we report our comprehensive results toward the oxidation of primary alcohols and aldehydes to acids via hydride transfer reactions mediated by 1-hydroxycyclohexyl phenyl ketone. Under the strong basic conditions of sodium tert-butoxide, the room temperature oxidations tolerate a range of functional groups, including vulnerable tert-butanesulfinamides, amines, sulfides, olefins, and heterocycles, and provide good to excellent yields. Most importantly, our oxidation procedure can be applied to chemoselective oxidation of primary alcohols and aldehydes to carboxylic acids in the presence of secondary alcohols.

Aminoalcohol Synthesis through Nonprecious Metal Catalysis: Enantioselective Cu-Catalyzed Reductive Coupling of Aldehydes and Allenamides.

Herein, we report the development of a Cu-catalyzed aminoallylation of aldehyde electrophiles through reductive coupling by circumventing the problematic competitive reduction of the aldehyde electrophile by a CuH catalyst. This leads to a highly diastereo- and enantioselective process for the synthesis of chiral 1,2-aminoalcohols containing secondary alcohol substitution. Cleavage of the N substituents on the reaction products was performed, allowing access to the other diastereomer of the aminoalcohol, which was investigated in the context of a synthesis of eligulstat.

Catalytic Activity of Ti-Modified MCM-41 for Oxidation of Secondary Alcohol with H2O2

Catalytic Activity of Ti-Modified MCM-41 for Oxidation of Secondary Alcohol with H2O2

β-Arylation of Racemic Secondary Benzylic Alcohols to Access Enantioenriched β-Arylated Alcohols.

The transformation of alcohols into value-added products is of great importance, as simple alcohols are widespread and can be easily derived from both fossil fuels and biomass. The selective functionalization of a sp3 C-H bond on the alkyl side chain of an alcohol over its hydroxyl group would offer an expedient route to expand the chemical space of alcohols but it remains a challenging task. Harnessing the borrowing hydrogen strategy, the β-arylation of secondary alcohols with aryl bromides has been achieved in this study, which allows for the selective functionalization of a β-Csp3 -H bond in an alcohol substrate. Under the catalysis of a Pd complex, secondary alcohols reacted with aryl bromides to afford 1,2-diaryl alcohols with broad substrate scope in the presence of a ketone additive. Furthermore, the enantioconvergent version of the reaction has also been realized, transforming racemic secondary alcohols into enantioenriched chiral 1,2-diaryl alcohols under the cooperative Pd and Ru catalysis. Mechanism studies indicate that the reactions are enabled by borrowing hydrogen catalysis.

β‐Arylation of Racemic Secondary Benzylic Alcohols to Access Enantioenriched β‐Arylated Alcohols

AbstractThe transformation of alcohols into value‐added products is of great importance, as simple alcohols are widespread and can be easily derived from both fossil fuels and biomass. The selective functionalization of a sp3 C−H bond on the alkyl side chain of an alcohol over its hydroxyl group would offer an expedient route to expand the chemical space of alcohols but it remains a challenging task. Harnessing the borrowing hydrogen strategy, the β‐arylation of secondary alcohols with aryl bromides has been achieved in this study, which allows for the selective functionalization of a β‐Csp3−H bond in an alcohol substrate. Under the catalysis of a Pd complex, secondary alcohols reacted with aryl bromides to afford 1,2‐diaryl alcohols with broad substrate scope in the presence of a ketone additive. Furthermore, the enantioconvergent version of the reaction has also been realized, transforming racemic secondary alcohols into enantioenriched chiral 1,2‐diaryl alcohols under the cooperative Pd and Ru catalysis. Mechanism studies indicate that the reactions are enabled by borrowing hydrogen catalysis.

Phosphine‐Free Pincer Ruthenium‐Catalyzed α‐Alkylation of Ketones with Secondary Alcohols to form β‐Branched Ketones

AbstractHerein, an efficient and expedient method was developed for α‐alkylation of aromatic ketones with secondary alcohols to produce β‐disubstituted ketones using phosphine‐free pincer ruthenium complexes as the catalyst. Single α‐alkylated ketone is produced in high yields even in reactions where a mixture of products is possible. Interestingly, challenging substrates such as unsubstituted and nonhindered acetophenone compounds are effectively alkylated under the reaction conditions. The scope of the reaction can span with a verities of aliphatic, cyclic, and acyclic secondary alcohols. Functionalization of a cholesterol molecule is also possible under the reaction conditions. Substitution on cyclohexyl ring afforded products as a mixture of diastereoisomers, wherein the major isomer is found as 1,4‐cis conformation of the cyclohexyl ring. Origin of the cis stereoselectivity in the alkylation process was explored by DFT calculation study. Mechanistic studies reveal that the dehydrogenation of alcohols follows a proton shuttle‐type of TS, involvement of cross‐aldol condensation and borrowing hydrogen catalysis. Notably, this selective, catalytic C−C bond forming reaction proceeds with low catalyst load, catalytic amount of base under air and produces H2O as the only byproduct, making the process environmentally benign and atom efficient.

Degradation of oxytetracycline by iron-manganese modified industrial lignin-based biochar activated peroxy-disulfate: Pathway and mechanistic analysis

In this study, high-performance Fe-Mn-modified industrial lignin-based biochar (FMBC) was successfully prepared to facilitate the efficient degradation of oxytetracycline by its driven sulfate radical-based advanced oxidation process with 90% degradation within 30 min. The results showed that oxygenated functional groups (e. g. hydroxyl, carbonyl, etc.) in industrial lignin-based biochar, the synergistic effect of transition metals Fe and Mn, and defective structures were the active sites for activation of peroxy-disulfate. SO4·− produced during the degradation process assumed a key function. Significantly, 38 intermediates were innovatively proposed for the first time in the system, and oxytetracycline was degraded in 7 ways, including deamidation, demethylation, hydroxylation, secondary alcohol oxidation, ring opening, dehydration, and carbonylation. A new perspective on the application of industrial lignin in the advanced oxidative degradation of organic pollutants was provided by this study.

Cascade Kinetic Model on Ethoxylation of Iso/Sec/n-Octanol Catalyzed by Alkali Hydroxides/Alkoxides and Its Experimental Verification

BackgroundEthoxylation kinetics of isomeric and secondary alcohols are crucial to the ethylene oxide (EO) distribution of alcohol ethoxylates, which might be influenced by basicity intensity of catalysts, similar as the ethoxylation of linear alcohols in the presence of alkali hydroxides/alkoxides catalysts; but may be affected by the steric hindrance caused by the branch chains of the ethoxylates. MethodsA kinetic model is derived based on SN2 mechanism of base-catalyzed ethoxylation of fatty alcohols, and experimentally verified with the initial kinetic characteristics in ethoxylation of 2-ethylhexanol (2-EH), 2-octanol (2-OT) and 1-octanol (1-OT) catalyzed by alkali hydroxides/alkoxides, CH3OK, CH3ONa, KOH and NaOH by GC monitoring the yields of each monodisperse oligo (ethylene glycol) iso/sec/n-octyl ethers. Significant findingsWith same catalyst, the ethoxylation rate constants of mono- (k0′) and di-adduction (k1′) products of iso/sec/n-octanol are dominated by the steric hindrance of the octanols, resulting higher k1′/k0′ for 2-EH and 2-OT than that of 1-OT; but the effect of the steric hindrance on initial EO distribution could be eliminated by stronger catalyst basicity. This finding suggests that the stronger catalyst basicity is beneficial to suppress the adverse steric hindrance of branch octanols (2-EH and 2-OT) on initial adduction rates, therefore resulting in a narrower EO distribution profile of the ethoxylates.

Boron Nitride- and Carbon-Supported Iridium–Iron Catalysts for Synthesizing Mono-Alcohols from Biomass-Derived Vicinal Diols

Hydrogenolysis of 1,2-diols to primary and secondary alcohols was investigated over nonoxide-supported Ir–FeOx catalysts using 1,2-butanediol (1,2-BuD) as a model substrate. Boron nitride (BN) has been found as an effective support for 1,2-BuD hydrogenolysis to secondary alcohol (2-butanol (2-BuOH)), similar to rutile TiO2 in our previous report. The addition of Fe species (Fe/Ir = 0.25 (optimal ratio)) to Ir/BN greatly improved the catalytic activity (23 times; 2-BuOH selectivity: ∼70%; highest yield: 64%). Meanwhile, some other supports including carbon supports gave primary alcohol (1-butanol (1-BuOH)) as the main product, which was less affected by the Fe addition or types of carbon supports. Activated carbon (C) provided the highest activity among the screened carbon-type supports. The 74% yield of 1-BuOH was obtained over Ir–FeOx/C. The selectivity pattern given by Ir–FeOx/BN much depends on its calcination temperature: a low calcination temperature (<673 K) led to the change in the selectivity pattern (∼70% of 2-BuOH to >70% of 1-BuOH). Ir–FeOx/BN was reusable for the 2-BuOH synthesis at least 4 times when the suitable calcination treatment (573 K, 1 h) was adopted for catalyst regeneration. In contrast, the addition of acid was necessary for regenerating the Ir–FeOx/C catalyst. Secondary alcohol with high selectivity (>60%) was achieved in related alcohol hydrogenolysis over Ir–FeOx/BN (Ir = 5 wt %, Fe/Ir = 0.25) such as 1,2-propanediol to 2-propanol, glycerol to 1,2-propanediol, and 1,3-butanediol to 2-BuOH. 2,3-Butanediol was formed in 32% yield from erythritol. Over Ir–FeOx/C or Ir/C, good yields of 1-alcohols were formed from 1,2-alkanediols, while reversible cyclization occurred for erythritol. Characterizations with X-ray diffraction, transmission electron microscopy–energy-dispersive X-ray spectroscopy, temperature-programmed reduction with H2, CO adsorption, diffuse reflectance infrared Fourier transform spectroscopy of adsorbed CO, X-ray absorption near edge structure, and extended X-ray absorption fine structure suggested that Ir–FeOx/C (Ir = 5 wt %, Fe/Ir = 0.25) consists of Ir particles (about 2 nm), highly distributed and isolated FeOx (valence: ∼2+), and residual acid. In Ir–FeOx/BN (Ir = 5 wt %, Fe/Ir = 0.25), Ir–Fe alloy (Fe0/(Fe0 + Ir0) = 20%) with a two-dimensional nanodendrite structure was formed. The production of primary alcohol over C-supported catalysts is via the route of dehydration + hydrogenation, where the residual acid catalyzes dehydration as the rate-determining step. The high selectivity to secondary alcohol over Ir–FeOx/BN was derived from two aspects: removal of acid (HCl) by calcination and generation of the active Ir–Fe alloy phase in the formation of secondary alcohol.

β‐Alkylation through Dehydrogenative Coupling of Primary Alcohols and Secondary Alcohols Catalyzed by Thioether‐Functionalized N‐Heterocyclic Carbene Ruthenium Complexes

AbstractA catalytic system for the direct β‐alkylation of secondary alcohol with primary alcohol has been investigated. In this work, a series of cationic Ru(II)(η6‐p‐cymene) complexes with thioether‐functionalized N‐heterocyclic carbene ligands (imidazole‐based 1 a–l and benzimidazole‐based 2 a–e) have been successfully synthesized and evaluated as catalysts. This investigation shows that modifications in the ligand moiety (thioether group and/or NHC core) have a strong effect on both selectivity and reactivity. Imidazole‐based complex 1 c, with only 1 mol % of catalyst loading, displayed the best catalytic activity as well as the highest selectivity for the β‐alcohol up to 98 : 2 for this tandem borrowing hydrogen/aldol methodology. Applied to a wide range of substrates, β‐alkylated secondary alcohols have been obtained in moderate yields, but generally with complete conversion and very high selectivity.

Understanding the Oxidative Properties of Nickel Oxyhydroxide in Alcohol Oxidation Reactions.

The NiOOH electrode is commonly used in electrochemical alcohol oxidations. Yet understanding the reaction mechanism is far from trivial. In many cases, the difficulty lies in the decoupling of the overlapping influence of chemical and electrochemical factors that not only govern the reaction pathway but also the crystal structure of the in situ formed oxyhydroxide. Here, we use a different approach to understand this system: we start with synthesizing pure forms of the two oxyhydroxides, β-NiOOH and γ-NiOOH. Then, using the oxidative dehydrogenation of three typical alcohols as the model reactions, we examine the reactivity and selectivity of each oxyhydroxide. While solvent has a clear effect on the reaction rate of β-NiOOH, the observed selectivity was found to be unaffected and remained over 95% for the dehydrogenation of both primary and secondary alcohols to aldehydes and ketones, respectively. Yet, high concentration of OH- in aqueous solvent promoted the preferential conversion of benzyl alcohol to benzoic acid. Thus, the formation of carboxylic compounds in the electrochemical oxidation without alkaline electrolyte is more likely to follow the direct electrochemical oxidation pathway. Overoxidation of NiOOH from the β- to γ-phase will affect the selectivity but not the reactivity with a sustained >95% conversion. The mechanistic examinations comprising kinetic isotope effects, Hammett analysis, and spin trapping studies reveal that benzyl alcohol is oxidatively dehydrogenated to benzaldehyde via two consecutive hydrogen atom transfer steps. This work offers the unique oxidative and catalytic properties of NiOOH in alcohol oxidation reactions, shedding light on the mechanistic understanding of the electrochemical alcohol conversion using NiOOH-based electrodes.

Chemoenzymatic Dynamic Kinetic Resolution of Secondary Alcohols and Amines Employing Copper-Based Photocatalysis

A tandem photo- and biocatalytic dynamic kinetic resolution of secondary alcohols and amines was achieved employing a commercially available lipase, Candida antarctica lipase B (CALB), and a heteroleptic copper complex. The process is an example of using copper-based photocatalysis to promote hydrogen atom transfer (HAT) processes employing thiyl radicals. Screening of 48 complexes and 5 disulfides identified Cu(dtbbpy)(DPEPhos)BF4 and (Ph3SiS)2 as an optimal catalyst system to promote the HAT process. The catalytic system represents a general system for radical-mediated racemization applicable to both aliphatic and aromatic alcohols and amines (18 examples, 60 → 97% yield, 76 → 99% ee).

Pd-Coordinated Salinidol-Modified Mixed MOF: An Excellent Active Center for Efficient Nitroarenes Reduction and Selective Oxidation of Alcohols.

Selective oxidation of active and inactive alcohol substrates and reduction of nitroarenes is a highly versatile conversion that remains a challenge in controlling functionality and adjustments in metal-organic frameworks (MOFs). On the other hand, it offers an attractive opportunity to expand their applications in designing the next generation of catalysts with improved performance. Herein, a novel mixed MOF consisting of supported 2-hydroxybenzamide (mixed MOF-salinidol) has been fabricated by post-synthetic modifications of mixed MOF. Subsequently, the prepared nanocomposites were modified to impart catalytic sites using palladium chloride ions mixed with MOF-salinidol/Pd (II). After successfully designing and structurally characterizing nanocomposites, we evaluated their activity in oxidizing primary and secondary alcohols using aerobic conditions with molecular oxygen and an air atmosphere. In addition, the stability of (mixed MOF-salinidol/Pd (II)) catalysts under catalytic conditions was also demonstrated by comparing the Fourier-transform infrared spectrum, scanning electron microscopy image, and ICP-OES method before and after catalysis. Based on the results, the active surface area of the synthesized nanocatalyst is large, which highlights its unique synergistic effect between post-synthetic modified MOF and Pd, and furthermore, the availability of catalytic sites from Pd, as demonstrated by outstanding catalytic activity.

Silver-Catalyzed Synthesis of Benzyl Ethers via Alkoxylation of Benzylic C(sp3)-H Bonds.

Alkoxylation of benzylic C(sp3)-H bonds has become one of the most important tools for the construction of benzyl ethers from feedstock chemicals. Herein, we reported a silver catalyzed alkoxylation of benzylic C(sp3)-H bonds employing potassium persulfate as an oxidant at room temperature. This strategy showed good functional-group tolerance, site selectivity, and chemoselectivity. The reaction proceeded smoothly in the presence of various primary, secondary, and tertiary alcohol nucleophiles, affording corresponding benzyl ethers. Combined experimental studies provided mechanistic insights into the possible radical pathways. Furthermore, a possible mechanism was proposed for this method.

Lipase catalyzed chemo-enzymatic synthesis of propranolol: A newer enzymatic approach

The biocatalytic processes are greener and safer alternatives for synthesis of drug and drug intermediates. This study reports one such approach of chemo-enzymatic synthesis of propranolol, a β-adrenergic receptor blocker. A green synthetic route was employed for synthesis of propranolol using enzymatic kinetic resolution. Racemic mixture of secondary alcohol [1-chloro-3-(naphthalen-1-yloxy)propan-2-ol] (RS)-5 was synthesized chemically in two step reaction and further its enzymatic kinetic resolution was carried out by using lipase to synthesize enantiomeric forms (R)-5 and S-(6) of propranolol. The kinetic resolution of (RS)-5 involves the transesterification of secondary racemic alcohol in which vinyl acetate is used as acyl donor. Initially, we screened commercially available lipases for kinetic resolution and of all the screened lipases Addzyme 001 showed the best results. The several reaction parameters such as organic solvent, acyl donor, temperature, reaction time and enzyme concentration were optimized to improve rate of reaction and to achieve maximum enantioselectivity. Addzyme 001 at 40 mg shows the maximum conversion rate of 49% using cyclohexane as the organic solvent, vinyl acetate as the acyl donor and it was found that the reaction yield was higher for (R)-5 along with the (S)-6 (eep = 98%, ees = 97%) at 40 °C in 48 h. Further, the treatment of (R)-5 with isopropyl amine resulted into formation of (S)-propranolol eep = 98%, and overall yield 29% independently. To synthesize (R)-propranolol, S-(6) acetate was produced enzymatically and was further deacylated by chemical hydrolysis for the production of (R)-propranolol. This study reports newer approach for synthesis of (R) and (S) propranolol using chemoenzymatic route.

Facile Selective Acetylation of Primary Alcohols Using Ethyl Acetate in Acidic Medium

AbstractEsters are demanded in a varied range of human industries and, although the classical methods for their production have been known since the late 19th century, the search for improved and sustainable protocols to prepare this class of compounds is yet invaluable. An efficient, fast and straightforward method has been stablished, using TsOH and EtOAc for the acetylation of primary alcohols, with yields ranging from 81 to 98 %, depending on the groups near the hydroxyl group. A slight variation of the protocol might also be applied to secondary alcohols with moderate to high yields (65 to 91 %). Finally, the methodology can be used to selectively acetylate primary and secondary alcohols in the presence of tertiary or phenolic hydroxyl groups.

Malachite green dye adsorption by jackfruit based activated carbon: Optimization, mass transfer simulation and surface area prediction

The exposure of basic dye towards human and environment can caused severe adverse effects. Hence, this study aimed (i) to optimize the adsorption of malachite green (MG) dye onto jackfruit peel based activated carbon (JPAC) by using response surface methodology (RSM) and (ii) to simulate the mass transfer process using Polymath mass transfer (PMT) model. The RSM revealed that the optimum activation temperature, activation time and potassium hydroxide (KOH) impregnation ratio, IR to be 782 °C, 1 h and 2.96 g/g which translated into 66.80 mg/g of MG adsorption and 34.52 % of JPAC's yield. The Freundlich isotherm model described the adsorption process the best while the Langmuir monolayer adsorption capacity was computed to be 376.33 mg/g. The kinetic data obeyed the PMT model the best where the rate constant, KPMT decreased from 1.20 to 0.41 h−1 as the MG concentration increased from 25 to 300 mg/L. Also, the PMT model was succeeded in predicting the surface area, aPMT of JPAC to be 807.77 m2/g and this value is comparable with the actual JPAC's mesopores surface area of 714.25 m2/g (error 11.58 %). The adsorption of MG onto JPAC was aided by several functional groups such as primary or secondary alcohol, non-bonded hydroxy group and methoxy through ion-dipole force and dipole-dipole force. Based on thermodynamic parameters, MG-JPAC adsorption system was endothermic in nature (∆H° = 37.12 kJ/mol), had an increment of randomness at solid-liquid interface (∆S° = 0.19 kJ/mol·K), spontaneous in nature (−20.11 kJ/mol) and physisorptionally governed (Ea = 9.46 kJ/mol).

Identification of key upregulated genes involved in foam cell formation and the modulatory role of statin therapy

We aimed to investigate the possible effect of statins on important genes/proteins involved in foam cell formation. The gene expression profile of the GSE9874, GSE54666, and GSE7138from the Omnibus database were usedto identify genes involved in foam cell formation. The protein-protein interaction (PPI) network and MCODE analysis of the intersection of three databases were analyzed. We used molecular docking analysis to investigate the possible interaction of different statins with the overexpressed hub genes obtained from PPI analysis. The intersection among the three datasets showed 54 upregulated and 26 down-regulated genes. The most critical overexpressed genes/proteins obtained as hub genes included: G6PD, NPC1, ABCA1, ABCG1, PGD, PLIN2, PPAP2B, and TXNRD1 based on PPI analysis. Functional enrichment analysis of 81 intersection DEGs at the biological process level focusing on the cholesterol metabolic process, secondary alcohol biosynthetic process and the cholesterol biosynthetic process. Under cellular components, the analysis confirmed that these 81 intersection DEGs were mainly applied in endoplasmic reticulum membrane, lysosome and lytic vacuole. The molecular functions were identified as sterol binding, oxidoreductase activity and NADP binding. The molecular docking showed that all statins appear to affect important protein targets overexpressed in foam cell formation. However, lipophilic statins, especially pitavastatin and lovastatin, had a greater effect than hydrophilic statins. The most significant protein target of all the overexpressed genes interacting with all statin types was ABCA1. The effect of lipophilic statins was shown for several critical proteins in foam cell formation.

MORPHOLOGICAL, CHEMICAL, AND THERMAL CHARACTERIZATION OF TOBACCO STALK FOR APPLICATION IN COMPOSITE MATERIALS

The main objective of this study is to analyze the use of tobacco stalk to develop new composite materials. For this purpose, tests and analyses were carried out to characterize the morphological, thermal, and chemical properties, as well as to obtain structural information about this plant waste. Morphology was analyzed by scanning electron microscopy (SEM). Thermogravimetry (TGA) was used to analyze mass loss and temperature degradation. Fourier-transform infrared spectroscopy (FTIR) was applied to determine the chemical composition. SEM showed the presence of filling components such as parenchyma and vascular elements of the xylem. FTIR showed the presence of elements such as absorbed water and primary and secondary aliphatic alcohols identified in cellulose, hemicelluloses, lignin, and carboxylic acids, among other substances. TGA showed cellulose degradation temperature between 250 and 350 °C. The test results indicate that tobacco stalks can be used to develop composite materials as fillers.