•K2S2O8 catalysed oxidative coupling of o-phenylene diamines and primary alcohols for the synthesis of benzimidazoles.•Light emitting properties of benzimidazoles were studied.•The absorption and ...emission spectra of compounds were experimentally and theoretically analysed.
We report the K2S2O8 catalyzed oxidative coupling of 1,2-diaminobenzenes and primary alcohols for the synthesis of benzimidazoles under metal-free conditions by utilizing oxygen from air as terminal oxidant and water in reaction medium. Also, the challenging aliphatic alcohols showed good performance in synthesis of benzimidazoles. We also carried out a detailed exploration of the mechanism. The metal-free conditions, commercially available oxidant and good functional-group tolerance are the advantages of the present strategy. Further, we have studied the light emitting properties of benzimidazoles. The absorption and emission spectra's of the compounds 5a and 6m were experimentally and computationally analysed. Also, HOMO/LUMO distributions of compound 5a and 6m were elucidated theoretically.
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The depicted PNN-Mn complex serves as a versatile catalyst for the dehydrogenative oxidation of a wide range of primary alcohols in water to form their corresponding carboxylic acids.
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...•A green and sustainable process for producing the carboxylic acids in aqueous media.•Manganese-promoted efficiently dehydrogenative oxidation of the alcohols into corresponding carboxylic acids.•The wide range of alcohols including either (hetero)aromatic or aliphatic types.•A possible mechanism regarding the oxidation process proposed through controlled experimentation.
Three classes of manganese(I) complex cation, (PNHN)Mn(CO)3Br (Mn1), (SNHN)Mn(CO)3Br (Mn2) and (NRNHN)Mn(CO)3Br (Mn3 (NMe), Mn4 (NEt), Mn5 (NiPr)), all incorporating a chelating 5,6,7,8-tetrahydro-8-quinolinamine (NHN) but distinct in their third donor atom, have been assessed as catalysts for the dehydrogenative oxidation of primary alcohols to form their corresponding carboxylic acids. Using water as solvent and NaOH as base, PNHN-containing Mn1 proved the most effective allowing both aromatic and aliphatic alcohols to be converted at 160 °C with excellent functional group tolerance (25 examples disclosed). A possible mechanism for this process, that makes use of an acceptorless dehydrogenation pathway, has been proposed and supported by targeted experimentation. Overall, these catalysts show great promise for applications in atom-economic carboxylic acid synthesis as well as in the development of organic hydride-based hydrogen storage systems.
Catalytic dehydration of primary alcohols has been developed for selective and sustainable linear alpha-olefins (LAOs) production. While Al2O3-based catalysts with tunable Lewis acidity and thermal ...stability have shown promise in enhancing LAO selectivity, challenges like acidity loss and compromised selectivity persist. This study addresses the need for an efficient catalyst system, synthesizing CeO2-doped Al2O3 catalysts with varying Ce loading and assessing their performance in the dehydration of 1-hexanol. Characterization using various techniques revealed that 10 wt% CeO2–Al2O3 (10CA) catalyst exhibited the highest 1-hexene yield (88.1%) under optimized conditions. CeO2 doping enhanced both acidic and basic strength, with excess Ce (>15%) leading to acidity and basicity loss. The 10CA catalyst demonstrated effectiveness across alcohols of different chain lengths (C5 and C8) at varying temperatures, showcasing the impact of carbon chain length on product selectivity. The scalability of the process was explored, with the 10CA catalyst successfully applied from lab-scale (0.0072 L/day) to bench-scale (4.33 L/day) reactions. The bench-scale reaction yielded 79.9% 1-hexene with 90.5% conversion of 1-hexanol and 88.2% selectivity for 1-hexene. The successful scale-up of the catalytic dehydration process using the 10CA catalyst underscores its potential as a pivotal component in the green economy, promoting sustainability and environmental friendliness in producing LAO.
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•CeO2-doped Al2O3 catalysts were synthesized and evaluated in the dehydration of 1-hexanol to 1-hexene.•Tuning the acidity and basicity significantly improved 1-hexene selectivity without compromising 1-hexanol conversion.•The chain length of the applied primary alcohol affected the product distribution.•Elevated reaction temperature was required to decompose dialkyl ethers with longer chain lengths.•The catalyst was successfully applied to a bench-scale reaction (4.33 L/day) of 1-hexanol dehydration.
• Odd-numbered primary alcohols are components of plant cuticular wax, but their biosynthesis remains unknown.
• We isolated a rice wax crystal-sparse leaf 5 (WSL5) gene using a map-based cloning ...strategy. The function of WSL5 was illustrated by overexpression and knockout in rice, heterologous expression in Arabidopsis and transient expression in tobacco leaves.
• WSL5 is predicted to encode a cytochrome P450 family member CYP96B5. The wsl5 mutant lacked crystalloid platelets on the surface of cuticle membrane, and its cuticle membrane was thicker than that of the wild-type. The wsl5 mutant is more tolerant to drought stress. The load of C23–C33 alkanes increased, whereas the C29 primary alcohol reduced significantly in wsl5 mutant and WSL5 knockout transgenic plants. Overexpression of WSL5 increased the C29 primary alcohol and decreased alkanes in rice leaves. Heterologous expression of WSL5 increased the C29 primary alcohol and decreased alkanes, secondary alcohol, and ketone in Arabidopsis stem wax. Transient expression of WSL5 in tobacco leaves also increased the production C29 primary alcohol.
• WSL5 catalyzes the terminal hydroxylation of alkanes, yielding odd-numbered primary alcohols, and is involved in the formation of epidermal wax crystals on rice leaf, affecting drought sensitivity.
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•The first tandem electrocatalyst for green synthesis of nitrile is designed and prepared.•Two active sites are co-localized on the catalyst surface, accelerating the cascade ...reaction.•The reaction pathway and product selectivity on different active sites are revealed.•Both high selectivity and high activity for the electrocatalytic synthesis of nitrile are achieved.
Nitriles are vital precursors in the production of pharmaceuticals, advanced materials and many other commercial chemicals. Conventional approaches for nitrile synthesis are limited by the utilization of highly toxic cyanide ion and harsh conditions. The electrochemical conversion of primary alcohols and ammonia to nitriles offers a cost-effective and green approach to prepare nitriles, which requires highly efficient and selective catalysts to drive the cascade reaction and minimize side reactions. Here, we demonstrate how nitriles can be selectively synthesized by electrocatalytic oxidation of benzyl alcohol and ammonia on NiCo nitride and oxide that are co-localized on carbon cloth (NiCo-N,O/CC) electrode. In this electrocatalyst, the oxidation from alcohols to aldehydes is mainly catalyzed by NiCo oxide, while the oxidation from imine to nitrile is mainly catalyzed by NiCo nitride, endorsing preferential oxidation and cascade reactions on these catalytic interfaces. A total faradaic efficiency of 52%, productivity rate of 35 μmol cm-2h−1 and 70.1% selectivity of nitriles was achieved at 1.53 V vs RHE. The two interface NiCo-N,O/CC tandem electrocatalyst revealed synergistic activity and selectivity superior to NiCo-O/CC with single interface. Our results demonstrate that the utilization of tandem catalytic mechanisms could create new prospects in designing electrocatalysts for cascade reactions.
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•This is a metal-free oxidative amination protocol for N-heterocycles.•Various primary alcohols are all tolerant.•Low environmental pollution, high atom-economy and good to excellent ...yields.
A general metal-free oxidative cyclization process has been developed for the synthesis of quinazolinones, benzothiadiazines and quinazolines. By this protocol, a range of substituted 2-aminobenzamides, 2-aminobenzenesulfonamide and 2-(aminomethyl)anilines react with various alcohols, leading to the desired annulated products smoothly. This protocol features many advantages as broad substrate scope, mild reaction conditions, low environmental pollution, high atom-economy and good to excellent yields.
The selective oxidation of primary alcohols to aldehydes by O2 instead of stoichiometric oxidants (for example, MnVII, CrVI, and OsIV) is an important but challenging process. Most heterogeneous ...catalytic systems (thermal and photocatalysis) require noble metals or harsh reaction conditions. Here we show that the Bi24O31Br10(OH)δ photocatalyst is very efficient in the selective oxidation of a series of aliphatic (carbon chain from C1 to C10) and aromatic alcohols to their corresponding aldehydes/ketones under visible‐light irradiation in air at room temperature, which would be challenging for conventional thermal and light‐driven processes. High quantum efficiencies (71 % and 55 % under 410 and 450 nm irradiation) are reached in a representative reaction, the oxidation of isopropanol. We propose that the outstanding performance of the Bi24O31Br10(OH)δ photocatalyst is associated with basic surface sites and active lattice oxygen that boost the dehydrogenation step in the photo‐oxidation of alcohols.
The great oxidizer: Bi24O31Br10(OH)δ is a very efficient photocatalyst in the selective oxidation of various aliphatic and aromatic alcohols to their corresponding aldehydes and ketones under visible‐light irradiation and ambient conditions. The outstanding performance is associated with basic surface sites and active lattice oxygen, which boost the dehydrogenation step in the photo‐oxidation.
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An environmentally benign, mild approach for synthesis of C-3 alkylated indoles, bisindolylmethanes and flavanones using alcohols at room temperature under visible light has been ...developed. The reported reaction conditions were favorable for a wide range of alcohols afforded good to excellent yields of the respective products. Additionally, the reaction system was successfully extended to the synthesis of flavanones from 2-hydroxyacetophenone. The low cost and air stable Knölker iron catalyst has been employed for the dehydrogenation of alcohols under photolysis that would usually require a higher temperature.
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•This review highlights the Light-promoted methodologies for the oxidation of alcohols.•Different photocatalysts like MOF-hybrids, metal hybrids, metal oxides, and metal free ...catalysts are discussed.•This study includes the critical analysis of the different reports along with comparative account.
Light-promoted methodologies can be considered ideal protocols for green and environment-friendly oxidation of alcohols, unlike many traditional methods and reagents that are toxic, hazardous, and low-yielding with tedious work up. The visible-light-induced photo redox catalysis to produce radical species has a broad scope in the selective oxidation of alcohols into their carbonyl compounds that have a broad application in industries and synthetic chemistry. In this comprehensive review, we targeted articles focused on photocatalytic transformations of primary aromatic alcohols to respective aldehydes. The photoconversion of alcohols into aldehydes was accelerated by MOF-hybrids, metal hybrids, metal oxides, and metal free catalysts. Overall, the present manuscript involves the different aspects of light promoted oxidation reactions of aromatic alcohols employing varied photocatalysts. This study also includes the critical analysis of the different reports available along with comparative account.
The direct α-alkylation of ketones with alcohol to synthesize important α-alkylated ketones and enones is an attractive procedure for C–C bond formation. High reaction temperatures are always needed ...for heterogeneous catalysis using non-noble metals, and switching product selectivity in one catalysis system remains a great challenge. In the present study, a visible-light-driven procedure for this reaction is proposed, using oxidized TiN photocatalysts under mild conditions, whereby the product selectivity can be well-tuned. Oxidized TiN photocatalysts with tunable surface N/O ratios were successfully synthesized through the facile and flexible thermal oxidation treatment of low-cost TiN nanopowder. The α-alkylation of acetophenone with benzyl alcohol to form the two important compounds chalcone and dihydrochalcone occurred even at room temperature and almost complete conversion was achieved at 100 °C under visible light. The proportion of the two products can be well-tuned by switching the surface N/O ratio of the synthesized photocatalysts. Visible light is demonstrated to affect the surface N/O ratio of the photocatalysts and contribute to tuning the product selectivity. Light intensity and action spectrum study proves that the generation of energetic charge carriers results in the observed activities under visible light, based on interband transitions of TiN or the ligand-to-metal charge transfer (LMCT) effect of the surface complex formed on TiO2. Thermal energy can be coupled with light energy within this photocatalytic system, which will facilitate the full use of solar energy. Different sequential reaction mechanisms on TiN and TiO2 are proposed to be responsible for the tunable product selectivity. The wide reaction scope, the fine conversion at a low light intensity, and the favorable reusability of photocatalysts prove the great application potential of this visible-light-driven procedure for the α-alkylation of ketones with primary alcohols.
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