Organic selenium compounds have attracted great attention from researchers because of their unique chemical reactivity and their wide applications in bioactive drugs, agricultural chemicals, and advanced functional materials. Therefore, the efficient and sustainable construction of C-Se bonds has become a core goal in modern synthetic chemistry. This review comprehensively summarizes the latest research progress in alkene selenylation reactions, a highly versatile strategy for constructing complex selenium-containing molecular skeletons. The article systematically outlines a variety of catalytic systems developed for these reactions, including transition-metal catalysis, visible- light catalysis, electrochemical methods, and small-molecule organocatalysis. This review focuses on the intrinsic mechanisms underlying selenium transfer and how cutting-edge synthesis methods address the limitations of traditional routes in operational costs, substrate scope, and environmental impact. By analyzing the unique advantages of various strategies, including enhanced sustainability, precise regioselectivity, and stereoselectivity, this review provides a comprehensive overview of the current state of synthetic research in this field. Finally, the article identifies existing challenges and outlines future directions for development, aiming to inspire the green, sustainable large-scale synthesis of high-value organic selenium derivatives and to promote further innovative research.
Introduction: The selective oxidation of allylic and conjugated alcohols to α,β- unsaturated aldehydes is a transformation of substantial interest in organic chemistry, both for mechanistic insights and synthetic value. The kinetics and mechanisms of oxidation of cinnamyl alcohol and crotyl alcohol by N-bromosuccinimide (NBS) have been systematically examined in aqueous alkaline media under pseudo-first-order conditions. Method: The reactions were monitored iodometrically by tracking the depletion of NBS. The progress of the reaction was observed by measuring the volume of sodium thiosulfate (hypo) solution required to titrate the unreacted NBS at various time intervals. Result: The rate of reaction demonstrates first-order dependence on alcohol and hydroxide ion concentrations, but a negative fractional order with respect to NBS is seen, suggesting the existence of a pre-equilibrium involving the oxidant species. The absence of any significant effect on ionic strength indicates that the rate-determining step involves neutral or weakly interacting species. discussion: The oxidation of cinnamyl alcohol is characterized by higher enthalpy of activation (ΔH# = 103.10 kJ mol⁻¹) and activation energy (Ea = 105.70 kJ mol⁻¹) compared to crotyl alcohol (ΔH# = 73.84 kJ mol⁻¹, Ea = 76.42 kJ mol⁻¹), showing a stronger energetic need for the former. In contrast, cinnamyl alcohol exhibits a positive entropy of activation (ΔS# = +29.27 J mol⁻¹ K⁻¹), whereas crotyl alcohol shows a negative value (ΔS# = −65.1 J mol⁻¹ K⁻¹), suggesting differences in the degree of structure in the activated complexes. Discussion: A comparative kinetic analysis reveals that crotyl alcohol undergoes oxidation at a faster rate than cinnamyl alcohol under identical conditions due to reduced steric hindrance and the absence of resonance stabilization, whereas the phenyl group in cinnamyl alcohol stabilizes the ground state and increases the energy barrier for oxidation. Activation parameters were examined using Arrhenius and Eyring treatments. The oxidation of cinnamyl alcohol is characterized by a higher enthalpy of activation (ΔH# = 103.10 kJ mol-1) and activation energy (Ea = 105.70 kJ mol-1) compared to crotyl alcohol (ΔH# = 73.84 kJ mol-1, Ea = 76.42 kJ mol-1), showing a stronger energetic need for the former. In contrast, cinnamyl alcohol exhibits a positive entropy of activation (ΔS# = +29.27 J mol-1 K- 1), whereas crotyl alcohol shows a negative value (ΔS# = −65.1 J mol-1 K-1), suggesting differences in the degree of structure in the activated complexes. Conclusion: Despite these discrepancies, both systems have essentially equal Gibbs free energies of activation, demonstrating an enthalpy–entropy compensating effect. A feasible process involving the creation of hypobromite species in alkaline media and a rate-determining hydride transfer step is proposed. The study reveals the substantial significance of structural and electrical variables in determining the oxidation kinetics of unsaturated alcohols and gives mechanistic insights pertinent to selective oxidation procedures.
Abstract: Asymmetric synthesis is a method of organic chemistry in which a reaction is designed to preferentially produce one enantiomer, leading to the formation of a product with specific stereochemistry. At present, asymmetric synthesis has become essential to modern chemistry because lots of biologically active molecules exist as enantiomers having different physiological effects. It helps researchers to control stereochemistry with high accuracy. This method lowers the need for separation of the racemic mixture, which makes the process more efficient and cost-effective. Asymmetric synthesis plays a significant role in organic synthesis as it has the ability to selectively produce a single enantiomer from an achiral or racemic intermediate. Its application in the field of organic synthesis and medicinal chemistry has grown significantly, primarily for the synthesis of complex natural products. It plays a key role in improving drug performance and selectivity by understanding the relationship between chemical structure and biological activity. Advances in asymmetric synthesis have enabled the efficient construction of complex chiral molecules with high enantioselectivity, facilitating the development of enantiomerically pure drugs, agrochemicals, and advanced materials. Additionally, the integration of advanced technologies such as artificial intelligence and computational modelling is expected to further enhance reaction design and predictability in asymmetric synthesis. Various catalysts, including organo- and metal-complex catalysts, have been discovered that promote and accelerate asymmetric synthesis. This review summarises the organocatalytic and organometallic approaches to asymmetric synthesis, highlighting the diverse catalysts employed, their synthetic applications, and future prospects in the field.
Abstract: GMC oxidoreductases are a superfamily that has a common FAD-dependent oxidation reaction mechanism. This article focuses on the commonalities and the differences between alkaline or acidic oxidoreductases like flavin-dependent Alcohol Dehydrogenase (ADH) and GMC. All three enzymes (GMCs, ADHs, and AOs) share a similar folding structure; all three have conserved motifs in their active sites; and all three oxidize alcohols (or alcohol-type substrates) by using molecular oxygen. However, there are many differences between how each oxidoreductase accomplishes the oxidation of alcohol through the various mechanistic pathways employed. For example, AOs catalyze the oxidation of aryl (phenol) to degrade lignin, whereas, in contrast, flavin-dependent oxidoreductases such as flavin-dependent alcohol dehydrogenases (ADH) produce the physiological result (breakdown of lignin) through the pathway of oxidation of aryl or alcohol. This paper explores the various mechanisms by which AOs differ from other GMC oxidoreductases (i.e., ADH) with regards to reaction mechanisms, kinetic control, and reactivity as a function of bond cleavage and redox properties. Furthermore, it describes the difference between the unidirectional stepwise reductive half-reaction used by AOs and ADH and the concerted hydrogen transfer mechanism utilized by AOs. Each of these enzymes contains structural features that give each its functionality. While a more detailed analysis of AOs' features can give biotechnological knowledge on how flavindependent oxidation of alcohols will take place, ultimately, there remains a significant opportunity within the biotechnological domain to exploit and engineer such mechanisms for commercial or other purposes.
Introduction: Carbohydrates play vital roles in both biological systems and materials science. In this study, an efficient synthetic route is presented for the preparation of novel carbohydrate– diol–sulfonate conjugates derived from sugars such as glucose and fructose. Through a sequence involving peracetylation, selective anomeric deacetylation using tin oxide, and subsequent sulfonation, reactive glycosyl donors were successfully synthesized. These compounds hold considerable potential for applications in advanced drug delivery systems. Methods: The study employs materials sourced from Sigma-Aldrich to develop an efficient synthetic route for novel carbohydrate–diol conjugates. Through a sequential process involving peracetylation, selective anomeric deacetylation, and diol coupling, glucose, fructose, lactose, mannose, and sucrose are transformed into reactive glycosyl donors through anomeric sulfonation. This synthetic strategy facilitates the construction of advanced molecular architectures with potential applications in carbohydrate- based molecular design. Results: Various saccharides were initially subjected to complete acetylation using acetic anhydride in the presence of sodium acetate as a catalyst. Subsequently, the anomeric protecting group was selectively removed using tin oxide, thereby freeing the anomeric hydroxyl group. The resulting intermediates were then reacted with various diols to generate new derivatives, which were subsequently sulfonated at the anomeric position using Methanesulfonyl Chloride (MsCl). The synthesized compounds were finally characterized and confirmed by spectroscopic analysis. Discussion: Saccharides undergo a sequence of acetylation, selective deacetylation, diol coupling, and anomeric sulfonation to yield novel carbohydrate–diol conjugates, which are confirmed through spectroscopic analysis. This synthetic approach efficiently generates reactive glycosyl donors, providing valuable building blocks for constructing advanced molecular architectures. Conclusion: This research presents a streamlined synthetic route for preparing carbohydrate–diol– sulfonate derivatives from readily available sugars through a sequence of selective acetylation, deacetylation, and sulfonation steps. The developed method enables the generation of structurally tunable compounds with enhanced reactivity as glycosyl donors, demonstrating promising potential for the development of glycoconjugate biomaterials and advanced drug delivery applications.
