Deoxyfluorination of 1°, 2°, and 3° Alcohols by Nonbasic O-H Activation and Lewis Acid-Catalyzed Fluoride Shuttling

Iron-Mediated One-Pot Dehydroxylative Cross-Electrophile Coupling of Alcohol with Disulfide for Thioether Synthesis by Using TCT as a Hydroxyl-Activating Agent

An efficient dehydroxythiolation between alcohols and disulfides using the widely abundant and cheapest iron as a reaction mediator was developed. The one-pot thiolation proceeded effectively via C-O bond activation with the aid of cyanuric chloride (TCT) as a hydroxyl-activating agent to give the corresponding thioethers in modest to excellent yields, displaying both a wide substrate scope (applicable to benzyl alcohol, allyl alcohol, and primary alkyl alcohol) and good functional group tolerance. In addition, diselenide was also proven to be an appropriate substrate for the protocol, and the reaction could be subjected to scale-up synthesis. Preliminary mechanistic examination revealed that transiently formed TCT-derived ether A, which is generated in situ via the reaction of TCT with alcohol, possibly serves as the pivotal intermediate of the cross-electrophile thioetherification.

Dual Activation of Organoboron for the Ion-Pair-Mediated Synthesis of Hindered Alkyl Fluorides

A novel electrochemical approach for the synthesis of hindered alkyl fluorides has been developed. The protocol grants access to a diverse array of tertiary and secondary alkyl fluorides using readily attainable organoboron precursors under mild conditions. The efficiency of the system stems from the dual activation of the redox-active borate intermediate, providing both electrophilic and nucleophilic reaction partners in the form of an internally generated ion pair.

Recent Advances in Fluorination Reactions via De-Carboxylative and De-Oxygenative Strategies: A Perspective

Organic fluorine compounds encompass a vast and diverse variety of species that possess unique biological activity due to the presence of fluorine atoms. Fluorine is highly electronegative, increases the lipophilicity (fat-solubility) and hydrophobicity (water-repellent nature) of molecules, often exhibit remarkable chemical and thermal stability. This is especially useful in drug design, as it can improve the bioavailability of pharmaceutical compounds and help them interact more effectively with biological membranes. The growing demand for fluorinated compounds in materials science, agrochemicals, and medicine has made selective fluorine incorporation into organic molecules a challenging but necessary component of modern organic synthesis. Development of C-F building blocks are invaluable in organic synthesis due to their ability to impart chemical stability, selectivity, and reactivity to organic molecules. This article provides a detailed analysis of two popular fluorination processes: deoxyfluorination and decarboxyfluorination. Deoxyfluorination is the process of enhancing the physicochemical properties of molecules by replacing hydroxyl groups with fluorine atoms. Decarboxyfluorination is a type of chemical reaction where transformation of carboxylic acid derivatives into fluorinated compounds. The various fluorinating reagents, mechanistic processes, synthetic uses and substrate scope are covered in this section. When combined, these novel transformation strategies provide effective and focused approaches to the production of C-F bonds, offering useful resources for obtaining fluorinated compounds. This review mainly focuses on the construction of fluorinated compounds via deoxygenative and decarboxylative fluorination since 2011. We hope this review offers a useful conceptual overview and inspires further advancements in the efficient construction of C-F bond.

Borane-Mediated Highly Secondary Selective Deoxyfluorination of Alcohols

Organofluorine compounds are vital across multiple sectors, hence highly selective methods to install fluorine are of considerable importance. The deoxyfluorination of alcohols is a key approach to prepare organofluorine compounds, however, a highly secondary (2°)-selective deoxyfluorination of alcohols has not been realized to date. Herein, we report that borane-mediated deoxyfluorination results in high 2°-selectivity in inter- and intra-molecular competition reactions versus primary (1°), tertiary (3°) and even benzylic (Bn) alcohols. This is an operationally simple method using only commercial reagents (e.g., Et3N ⋅ 3HF) that starts from the alcohol which is converted to the O-alkyl-N-H-isourea in situ. The origin of the high 2°-selectivity was elucidated to be due to the relative barriers to carbodiimide elimination from the O-alkyl-N-(BR2)-isoureas. As the selectivity controlling step does not involve fluoride, this borane-mediated approach can be applied to other nucleophiles, as demonstrated by 2°-selective deoxychlorination using HCl occurring in preference to substitution of 1° and Bn analogues. This borane-mediated nucleophilic substitution therefore provides a new approach to circumvent the selectivity limitations inherent in classical SN2 and SN1 type reactions.

Exploring Chemical Reaction Space with Machine Learning Models: Representation and Feature Perspective

Chemical reactions serve as foundational building blocks for organic chemistry and drug design. In the era of large AI models, data-driven approaches have emerged to innovate the design of novel reactions, optimize existing ones for higher yields, and discover new pathways for synthesizing chemical structures comprehensively. To effectively address these challenges with machine learning models, it is imperative to derive robust and informative representations or engage in feature engineering using extensive data sets of reactions. This work aims to provide a comprehensive review of established reaction featurization approaches, offering insights into the selection of representations and the design of features for a wide array of tasks. The advantages and limitations of employing SMILES, molecular fingerprints, molecular graphs, and physics-based properties are meticulously elaborated. Solutions to bridge the gap between different representations will also be critically evaluated. Additionally, we introduce a new frontier in chemical reaction pretraining, holding promise as an innovative yet unexplored avenue.

Ligand-enforced geometric constraints and associated reactivity in p-block compounds

The geometry at an element centre can generally be predicted based on the number of electron pairs around it using valence shell electron pair repulsion (VSEPR) theory. Strategies to distort p-block compounds away from these predicted geometries have gained considerable interest due to the unique structural outcomes, spectroscopic properties or reactivity patterns engendered by such distortion. This review presents an up-to-date group-wise summary of this exciting and rapidly growing field with a focus on understanding how the ligand employed unlocks structural features, which in turn influences the associated reactivity. Relevant geometrically constrained compounds from groups 13-16 are discussed, along with selected stoichiometric and catalytic reactions. Several areas for advancement in this field are also discussed. Collectively, this review advances the notion of geometric tuning as an important lever, alongside electronic and steric tuning, in controlling bonding and reactivity at p-block centres.

Geometrically Deformed and Conformationally Rigid Phosphorus Trisamides Featuring an Unsymmetrical Backbone

Nonclassical P(III) centers have attracted much attention in recent years. Incorporating a P(III) center in a rigid bicyclic platform offers a particularly attractive way to invoke significant geometric distortion of the phosphorus atom that may in turn induce unusual reactivity. Although still relatively scarcely explored, phosphorus centers enforced in a non-C3 symmetry have gained significant traction lately. However, the current scaffolds are based on a relatively limited set of design principles and ligand platforms associated therewith. This work is focussed on the synthesis as well as versatile oxidation, addition and coordination chemistry of a geometrically distorted P(III) species featuring a synthetically modular, nonsymmetric trisamine platform derived from 2-(methylamino)-N-(2-(methylamino)phenyl)benzenesulfonamide.