Secondary Alcohols Research Articles

Efficient Hydroboration of Ketones and Imines Using Amidophosphine‐Borane Under Catalyst‐Free Conditions

AbstractWe report here the use of amidophosphine borane {(BH₃)₂(PPh)₂N(CH₂)C₆H₅} as a competent reducing agent for the hydroboration of ketones and imines under mild and catalyst‐free reaction conditions yielding the corresponding secondary alcohols and secondary amines after aqueous work. Solid amidophosphine boranes, which are easy to synthesize, and easy to handle demonstrated excellent reactivity and functional group tolerance toward a wide variety of ketones and imines, including aromatic, heteroaromatic, and aliphatic derivatives with electron‐withdrawing and electron‐donating substitutions, thus showing excellent chemoselectivity.

A Machine Learning-Guided Approach to Navigate the Substrate Activity Scope of Galactose Oxidase: Application in the Conversion of Pharmaceutically Relevant Bulky Secondary Alcohols

A Machine Learning-Guided Approach to Navigate the Substrate Activity Scope of Galactose Oxidase: Application in the Conversion of Pharmaceutically Relevant Bulky Secondary Alcohols

Switching the Stereopreference of TeSADH: Enabling Anti‐Prelog Asymmetric Reduction of Aryl‐Ring‐Containing Ketones

AbstractThe biocatalytic asymmetric reduction of prochiral ketones offers a promising approach for producing optically active secondary alcohols. Alcohol dehydrogenases (ADHs) are enzymes that facilitate the reversible conversion of prochiral ketones into their corresponding optically active secondary alcohols, and thus are pivotal for this process. Most ADHs adhere to Prelog's rule in determining the stereopreference for the asymmetric reduction of prochiral ketones. This study focuses on the ΔP84/A85G mutation of TeSADH, demonstrating its capability to reduce aryl‐ring‐containing ketones to their corresponding alcohols in anti‐Prelog mode with high stereoselectivities. The study also highlights the crucial role of P84 in switching the stereopreference of TeSADH in the asymmetric reduction of aryl‐ring‐containing ketones. Furthermore, this mutant exhibits a broad substrate scope, including substrates accepted by the previously reported W110 mutants of TeSADH with opposite stereopreference. The ability to create mutants of the same enzyme with opposite stereopreferences presents intriguing opportunities for fascinating transformations, such as bienzymatic racemization, which can be utilized in dynamic kinetic resolution, and stereoinversion using two enantiocomplementary mutants of the same enzyme.

An improved synthesis of alkyl AMP esters

Enzymes belonging to the Acyl-CoA/NRPS/Luciferase (ANL) superfamily of enzymes, are significant targets in drug development. One member of this superfamily is Acetyl-CoA Synthetase (ACS). This enzyme is an emerging target for the treatment of various infectious diseases and cancer. Alkyl AMP esters have emerged as potent inhibitors of ACS. Previous methods for synthesizing these esters often involved water-based reactions or necessitate purification through reverse phase prep-HPLC or ion-exchange chromatography. To address these challenges, we developed a new approach utilizing 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC·HCl) to couple 5′-adenylic acid to the corresponding alcohol, utilizing triethylamine as the base. This method yielded primary, secondary, unsaturated, and cyclic alcohols in excellent yields. Importantly, we optimized the reaction conditions to achieve excellent yield and purity without the need for reverse phase prep-HPLC or ion exchange chromatography. Instead, purification was achieved through silica gel chromatography using Biotage ® Sfar spherical silica gel.

Overview of Baker's Yeast as a Biocatalyst

Biocatalysis is an approach to green chemistry. A crucial step in the synthesis of or-ganic compounds is the reduction of aldehydes and ketones to secondary alcohols. The use of a biocatalyst, such as enzymes or entire cells, has not affected this process.. It offers great selectiv-ity, high specificity, and an environmentally friendly approach to synthesis. Dried baker's yeast mediates the conversion of optically active alcohols from aromatic aldehydes and ketones. This work highlights applications of Baker's yeast in synthesizing pharmaceutical intermediates and chiral building blocks, demonstrating its practical relevance. Sustainable technology is based on the ideas and measurements of sustainable development and green for good enantioselectivity across several organic solvents.

Rhodium-Catalyzed Asymmetric Transfer Hydrogenation of Aryl Ketones Involving Free Phenolic Hydroxyl Group(s).

A straightforward asymmetric transfer hydrogenation for accessing enantiomerically enriched secondary benzyl alcohols involving free phenolic hydroxyl group(s) under mild conditions was developed. Various of optical pure aryl alcohols with a remarkable functional group compatibility were achieved with 78 %-97 % yields, 84 %->99 % ee's and up to 10 000 TON. This rhodium-catalyzed reaction could be performed in a gram-scale without loss of the efficiency. Furthermore, the synthetic utility has also been demonstrated in the asymmetric synthesis of (S)-adrenaline and (S)-phenylephrine.

TEMPO‐Catalyzed Continuous‐Flow Aerobic Oxidations of Alcohols on Silica

Abstract2,2,6,6′‐Tetramethylpiperidine‐N‐oxyl (TEMPO) is a highly efficient oxidation catalyst, valued for its environmentally benign nature, particularly in comparison to transition‐metal catalysts. Despite their merits, TEMPO‐based catalysts are not notably cost‐effective. Immobilization of TEMPO onto supports offers a promising strategy to overcome this limitation. In this work, we present the synthesis and application of immobilized TEMPO catalysts 2–5, prepared via a straightforward condensation reaction, for the aerobic oxidation of alcohols. These catalysts demonstrate remarkable activity for alcohol oxidations under continuous‐flow conditions, employing nitric acid as the co‐catalyst. Notably, catalyst 2 immobilized by COOH silica gel exhibits outstanding performance for the oxidation of benzyl alcohol by oxygen gas, achieving a turnover frequency (TOF) of 15 h−1 and a turnover number (TON) exceeding 300. Catalyst 2 further demonstrates broad substrate scope, effectively oxidizing primary, secondary, and benzylic alcohols. Post‐reaction analysis of spent catalyst 2 reveals that deactivation primarily stems from nitrosation of the N−O bond. Interestingly, the amide moiety remains intact despite the harsh acidic reaction conditions.

Organophotocatalyst Enabled Deoxycyclopropanation of Alcohols.

Cyclopropane fragments, which widely exist in marketed drugs and natural products, can confer special pharmacological properties to small-molecule drugs. Therefore, developing methods to construct cyclopropanes is of great significance. Nevertheless, the introduction of cyclopropane primarily relies on already-formed cyclopropyl groups, which significantly restricts the diversity of cyclopropane skeletons. Late-stage direct cyclopropanation is still a challenging task. Herein, a photo-induced intermolecular deoxycyclopropanation reaction that employs alcohols as substrates, and 1 mol.% of 2,3,5,6-tetrakis(carbazol-9-yl)-1,4-dicyanobenzene (4CzTPN)as organophotocatalyst is reported. This method proceeds with high transformation efficiency (up to 98% yield) and exhibits broad functional group tolerance, such as primary, secondary, and tertiary alcohols as well as various activated β-halogenated alkenes. This process is mild, easy to operate, and has low equipment requirements. The power of this technology is demonstrated by the late-stage functionalization of five marketed drugs and five natural products.

Palladium-Catalyzed Ortho Alkoxylation of Oxazoline Derivatives: An Avenue to Reach Meta-Substituted Electron-Rich Arenes Exploiting Oxazoline as a Removeable Directing Group.

An efficient and highly regioselective palladium-catalyzed oxazoline-directed alkoxylation is reported. The reaction proceeds under air and mild temperatures (60 °C). A series of alcohols can be used as alkoxylating agents and concomitantly act as reaction solvents, whereas primary and secondary alcohols are tolerated. Furthermore, fluorinated alcohols can be applied as well, introducing pharmaceutically relevant fluorine-containing groups. 1,3-Dialkoxylated products can be further subjected to hydrolysis transforming the oxazoline-directing group to a carboxylic acid, which can be removed by decarboxylation if desired. This approach demonstrates the capability to reverse the conventional site selectivity of electrophilic aromatic substitution reactions, since it allows the synthesis of arenes with two electron-donating groups in a 1,3-relationship.

A reagent-free, sequence-dependent in situ peptide self-cyclization strategy under physiological condition

Cyclic peptides are an important class of bioactive molecules used as drugs as well as biomolecular probes. Peptide cyclization under the physiological environment, without added chemicals or reagents, would be a highly useful technique for in situ applications. A simple, highly efficient, and green procedure for side-chain to side-chain in situ peptide cyclization is established here at the physiological condition. The methodology further allows the release of small biologically active molecules through peptide self-cyclization. Bioactive molecules, as well as other organic leaving groups (having primary or secondary alcohol as a functional group), were conjugated to a short peptide RXE sequence (X = Pro/Ala/Gly). The peptides were designed to undergo cyclization under physiological conditions and release the covalently attached chemotherapeutic drug and nucleobases, in a controlled manner. In vitro studies were performed in detail, with optimized physiological parameters, to understand the kinetics as well as the mechanism of self-cyclization. The mechanism of action was investigated by HPLC and ESI-Mass spectrometry. The conformational change, due to cyclization of the peptides, was monitored by CD spectroscopy. The present concept of peptide self-cyclization leading to a bond cleavage could be a potential method of delivery of small, bioactive molecules such as chemotherapeutic drugs.

Determination of Chain Transfer Constants of Alcohols for High‐Pressure Polyethylene Polymerization

AbstractIn low‐density polyethylene (LDPE) production, low‐molecular‐weight species are used as chain transfer agents (CTAs). They reduce the degree of polymerization, which has an impact on the polymer properties, such as processability. To specifically adjust the product properties, a detailed understanding of the transfer kinetics to CTAs is indispensable. Thus, the transfer activity of various primary, secondary, and tertiary alcohols as well as diols was investigated experimentally between 120 °C and 250 °C at 2000 bar. The results were evaluated using the Mayo and chain length distribution (CLD) method, and the latter was found to give more reliable results. It was observed that the hydroxy group systematically increases transfer activity compared to alkanes. Additionally, a linear increase of transfer activity with the number of hydrogen atoms is found.

Selective C- and N-Methylation of Secondary Alcohols and Nitroaromatics with Methanol Catalyzed by a New Ru(II)-Azo Complex

Selective <i>C</i>- and <i>N</i>-Methylation of Secondary Alcohols and Nitroaromatics with Methanol Catalyzed by a New Ru(II)-Azo Complex

Promoting role of Ru species on Ir-Fe/BN catalyst in 1,2-diols hydrogenolysis to secondary alcohols

Noble metal-based-bimetallic catalysts have been highly investigated and applied in wide applications including biomass transformation via regioselective C−O hydrogenolysis while further modification especially with noble metal is highly promising yet still under investigation. Herein, Ru was found as an effective modifier among the screened noble metals (Ru, Pt, Rh, Pd, Au, and Ag) for Ir-Fe/BN (Ir = 5 wt%, Fe/Ir = 0.25) catalyst in terminal C−O hydrogenolysis of 1,2-butanediol (1,2-BuD) to 2-butanol (2-BuOH). Only trace amount of Ru (up to 0.5 wt%) was effective in terms of high 2-BuOH selectivity (> 60%) and activity (about twice). Larger amount of Ru species (3 wt%) highly enhanced the activity but gave low selectivity to 2-BuOH with by-products of terminal C−C bond scission. Optimized catalyst (Ru(0.5)-Ir-Fe/BN) was reusable at least 4 times and gave moderate 2-BuOH yield (47%) in hydrogenolysis of 1,2-BuD. The promoting effect of Ru addition (0.5 wt%) to Ir-Fe/BN on hydrogenolysis of various alcohols was also confirmed. Combining catalytic tests with various characterizations, the promotion mechanism of Ru species in trimetallic catalysts was clarified. The Ru species in Ru(0.5)-Ir-Fe/BN form alloy with Ir and are enriched at the interface with BN surface, and direct interaction between Ru and Fe was not necessary in Ru-Ir-Fe alloy. The interface of Ir and Fe on the surface of Ir-Fe alloy may work as active sites for 1,2-diols to secondary alcohols via direct C−O hydrogenolysis, in which Ru-modified Ir activates H2 to form hydride-like species. The activity of Ru species in C−C bond cleavage was highly suppressed due to the direct interaction with Ir species and less exposed to substrate. Larger loading amount of Ru species (3 wt%) led to the formation Ru-rich trimetallic alloy, which further works as active sites for C−C bond scission.

Hydrogen Bonding Interaction Enabled Ru(III)‐Catalyzed Synthesis of (Multi)‐Substituted Pyridines

AbstractHerein, we report a cost‐effective synthesis of various multi‐substituted pyridine derivatives, especially 2‐aryl pyridines, using secondary alcohols and 1,3‐diol as the primary feedstock with ammonium acetate serving as nitrogen donor, catalyzed by a new well‐defined singlet mono‐radical Ru(III)‐catalyst featuring a cyclopentadienyl group, one PPh3, and a redox‐active scaffold −N1‐(2‐aminophenyl)benzene‐1,2‐diamine having a pendant ‐NH2 arm. The ‐NH2 arm of the catalyst facilitates the generation of the critical reactive intermediates by enhancing the electrophilicity of the carbonyl carbon center of the diols or diketones by forming hydrogen bonds, making it more catalytically effective over the similar other Ru‐catalysts having no pendant ‐NH2 arm. The Ru‐catalyst also functionalizes 2‐aryl pyridine moieties with different coupling partners, such as aryl iodides, terminal alkynes, and styrene derivatives at the o‐position of the phenyl ring.

Model catalytic studies on the thermal dehydrogenation of the benzaldehyde/cyclohexylmethanol LOHC system on Pt(111).

We investigated the dehydrogenation reaction and the thermal robustness of the liquid organic hydrogen carrier (LOHC) couple benzaldehyde/cyclohexylmethanol on a Pt(111) model catalyst in situ in synchrotron radiation photoelectron spectroscopy- and complementary temperature-programmed desorption experiments. The system stores hydrogen in a cyclohexyl group and a primary alcohol functionality and achieves an attractive hydrogen storage capacity of 7.0 mass%. We observed a stepwise dehydrogenation mechanism, characterized by a low temperature dehydrogenation of the alcohol group at 235 K. However, stability limitations challenge the system's applicability as reversible hydrogen storage solution, as the resultant aldehyde was found to decompose during the dehydrogenation of its cyclohexyl group (between 250 and 350 K). A comparison of cyclohexylmethanol with the structurally related secondary alcohol (1-cyclo-hexylethanol; 6.3 mass% hydrogen) revealed a parallel stepwise dehydrogenation pattern for both compounds, but a technically relevant superior thermal robustness of the latter. This demonstrates the influence of the alcohol group's substitution degree on the dehydrogenation characteristics of alcohol-functionalized LOHC compounds. Density functional theory calculations are in good agreement with the experimentally observed stability trend.

Multifunctional Polymer Synthesis via Sequential Postpolymerization Modification Using a Single Aldehyde Repeat Unit: Allylation and Orthogonal Esterification and Thiol-ene Reaction.

Herein, we present a highly efficient method for synthesizing multifunctional polymers. This method involves the sequential postpolymerization modification (PPM) of a highly reactive aldehyde polymer. We introduce an allylic alcohol functionality into the polymer backbone via Barbier-type allylation, a process facilitated by easy-to-handle indium(0) powder. This step enables the formation of orthogonal pendants, secondary alcohol, and terminal alkene, which can be further functionalized through esterification and thiol-ene click reactions. All of these processes are carried out under mild conditions, ensuring high efficiency and a wide range of functional groups. Our study underscores PPM's operational simplicity and versatility in developing advanced polymer materials and expanding the scope of multifunctional polymer design.

Cobalt-Catalyzed Divergence in C(sp3)-H Functionalization of 9H-Fluorene: A Streamlined Approach Utilizing Alcohols.

Sustainable chemical production demands the creation of innovative catalysts and catalytic technologies. While the development of coherent and robust catalytic systems using earth-abundant transition metals is essential, it remains a significant challenge. Herein, an expedient divergence strategy for tandem dehydrogenative C(sp3)-H alkylation and cyclization reactions of 9H-fluorene using a newly developed N,N-bidentate cobalt catalytic system is developed. This method capitalizes on the use of abundant and readily accessible alcohol. Demonstrating wide-ranging applicability, the catalytic protocol successfully integrated a diverse array of fluorenes and alcohols. This includes benzylic, heteroaromatic, and aliphatic primary and secondary alcohols, amassing a total of 75 distinct examples. When applied to sterically bulky alcohols, the reaction preferentially undergoes alkenylation, yielding a tetrasubstituted olefin as the main product. In the case of diols, the expected outcome is Dual-fluorescence at both terminal positions. This process leads to difluorination, followed by a cyclization step, culminating in the formation of a relatively unprecedented spiro compound. The scalability of this method has been validated through gram-scale synthesis. Control experiments have shed light on the reaction mechanism, indicating that it progresses through an unsaturated intermediate and adheres to the borrowing hydrogen pathway.

Manifestation of Anxiety in People with an Addictive (Alcoholic) Form of Behavior

The focus of this article is on the problem of addictive behavior, namely, the psychological characteristics of a person with alcohol dependence. The aim is to analyze and generalize the factors that contribute to the formation of addictive behavior and to highlight the socio-psychological nature of this dependence in relation to anxiety. A number of important psychological and pedagogical issues regarding the factors contributing to the formation of this form of behavior are considered. The features that help to understand and uncover the mechanisms of their action are also considered. It is pointed out that in the study of the personality of people with alcohol dependence, one of the dominant points of view is the phenomenon of anxiety. The researchers' interest is focused on understanding the nature of anxiety as a trigger. The psychology of anxiety is considered as an individually psychological feature of a person who is in one or another difficult situation for him. Recognizing the complexity of studying the personality of people with alcohol dependence, it emphasizes such characteristic features for the majority as short temper, lack of compromise, intolerance to the opinions of others, resentment, a tendency to revenge, a high level of conflict. It is impossible not to pay attention to the fact that there is a contradictory character in the conclusions about the ratio of primary and secondary anxiety and alcohol consumption as two mutually determining factors. An attempt is made to explain this discrepancy based on research. The different types of work significantly enrich our understanding of this phenomenon. Studies have shown that this category of people has a higher level of situational and personal anxiety. The revealed nature of the relationship indicates the peculiarities of conflict in this category. The data obtained show an example of traits that are interrelated with it.

Organophotocatalytic Selective Deuteration of Metabolically Labile Heteroatom Adjacent C-H Bonds via H/D Exchange with D2O.

We report a general approach for efficient deuteration of the metabolically labile α-C-H bonds of widespread amides and amines. Temporarily masking the secondary amine group as a carbamate allows an unprecedented photoredox hydrogen atom transfer-promoted α-carbamyl radical formation for efficient H/D exchange with D2O. The mild protocol delivers structurally diverse α-deuterated secondary amines including "privileged" piperidine and piperazine structures highly regioselectively with excellent levels of deuterium incorporation (≤100%). Furthermore, we successfully implemented the strategy for α-deuteration of amides, lactams, and ureas with high regioselectivity and high levels of D incorporation. Finally, the observed efficient deuteration of secondary alcohol moieties in late-stage modification of complex amine-containing pharmaceuticals allows for the development of a viable method for efficient α-deuteration of the important functionality.

Temperature dependence of structural evolution and fragility of glass-forming monohydroxy alcohols

The dynamic, structural, and thermodynamic properties of thirty-four monohydroxy alcohols with varying molecular architectures, including differences in alkyl chain length, OH group position, and presence/type of carbon ring, were investigated. Results of dielectric spectroscopy, temperature-modulated differential scanning calorimetry, and X-ray diffraction, were analyzed to verify correlations between the glass transition temperature (Tg), molar mass (M), boiling temperature (Tb), dynamic and thermodynamic fragility (mα and m), and the structurally related parameter (S). The collected data revealed that primary and secondary alcohols generally adhere to the correlations Tg ∝ M0.51 and Tb = 132 + 2.2Tg, while alcohols with phenyl ring deviate from these trends. Moreover, it was found that the changes in the width of the main diffraction peak normalized by the peak position ΔQM/QM over temperature scaled by Tg correspond to the variable m. However, the extent and course of this relationship varies across alcohols belonging to different structural groups. The weakest correlation and largest scatter between S and m occur for phenyl alcohols exhibiting the greatest structural heterogeneity. This study underscores the challenges of establishing universal correlations between physical variables within the diverse group of monohydroxy alcohols and emphasizes the importance of considering specific molecular features in predicting glass-forming behaviour.