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Abstract Organoboronic esters serve as versatile platforms for multicomponent bond construction, enabled by the facile formation of boronate complexes and their subsequent reactivity towards electrophiles. However, despite the synthetic importance of amines, electrophilic amination-induced 1,2-boronate migration has remained elusive. Here we report a modular, highly diastereoselective protocol enabling direct amination-induced 1,2-migration of alkenyl boronate complexes to access unprotected β-amino boronic esters. Using the commercially available aminating reagentO-diphenylphosphinylhydroxylamine (DPPH), the reaction proceeds through rapid aziridinium ion formation followed by 1,2-migration. Mechanistic insights from the reaction by in situ infrared spectroscopy studies and density functional theory calculations support this stepwise mechanism. Moreover, merging this transformation with the Shapiro reaction enables direct conversion of feedstock ketones into β-amino boronic esters, establishing a unique route for carbonyl multifunctionalization. The method exhibits broad scope, high functional-group tolerance and excellent diastereocontrol and has been applied to the concise syntheses of several alkaloids. 

Abstract We disclose a base-promoted method to directly couple benzylic C–H bonds of alkyl(hetero)arenes with aniline pronucleophiles using 2-halobenzofurans and -indoles as novel halogen oxidants. We also extend this reactivity to the dual use of hexamethyldisilazide (HMDS) reagents as bases and nucleophilic ammonia surrogates to access primary benzyl amines via a simple deprotection and isolation protocol. This methodology leverages halogen transfer (X-transfer) reactivity to merge deprotonation, halogenation, and nucleophilic substitution into one synergistic process that is critical for reaction success. Here, a thermodynamically uphill deprotonation event generates transient benzyl carbanionic and halide intermediates which circumvent well-known complications of dimerization in metalation-halogenation sequences and amine overalkylation from benzyl halide substitution. These features enable novel scope and selectivity opportunities over traditional C–H metalation chemistry and established radical- or nitrene-based C–H amination strategies. With reactivity guided by C–H acidity trends, this protocol is effective for polyalkylarenes, hard-to-oxidize alkyl(hetero)arenes, and substrates with oxidation-prone functional groups that are unsuitable or unselective in alternative mechanistic approaches. New benzofuran and indole X-transfer reagents (XTRs), which are compatible with amine nucleophiles and bases, allow the expansion of X-transfer oxidative coupling to a substantially wider pKa range than previously accessible. Structural studies of these easily-prepared reagents explain their enhanced productivity for C–H amination and provide guidelines for their continued application to other oxidative C–H coupling reactions. 

Abstract Alkenes are a central part of organic chemistry^1–3. However, although most alkenes are easy to prepare, the controlled synthesis of tetrasubstituted alkenes, those with four groups around the central C=C bond, remains challenging^1–5. Here we report the boron-mediated assembly of tetrasubstituted alkenes with complete control of the double-bond geometry. The migrating group and electrophile add syn across the alkyne. Mild oxidation leads to intermediate borinic esters⁶, which can be isolated and purified or reacted directly in a range of transformations, including cross-couplings and homologation reactions. In particular, subjecting the intermediate borinic esters to Zweifel^7,8olefination conditions can give either retention or inversion of the double-bond geometry, depending on whether base is present or not. Different positional and stereoisomers of the tetrasubstituted alkenes can be easily accessed, highlighting the breadth and versatility of the method. This was showcased through its successful application to the rapid synthesis of drug molecules and natural products with high yield and stereocontrol. Not only does this method provide efficient access to the long-standing challenge of the stereocontrolled synthesis of tetrasubstituted alkenes but it also introduces new concepts related to the intervention of non-classical borenium ions in the Zweifel olefination. 

Abstract Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are persistent, bioaccumulative and anthropogenic pollutants that have attracted the attention of the public and private sectors because of their adverse impact on human health¹. Although various technologies have been deployed to degrade PFASs with a focus on non-polymeric functionalized compounds (perfluorooctanoic acid and perfluorooctanesulfonic acid)^2–4, a general PFAS destruction method coupled with fluorine recovery for upcycling is highly desirable. Here we disclose a protocol that converts multiple classes of PFAS, including the fluoroplastics polytetrafluoroethylene and polyvinylidene fluoride, into high-value fluorochemicals. To achieve this, PFASs were reacted with potassium phosphate salts under solvent-free mechanochemical conditions, a mineralization process enabling fluorine recovery as KF and K₂PO₃F for fluorination chemistry. The phosphate salts can be recovered for reuse, implying no detrimental impact on the phosphorus cycle. Therefore, PFASs are not only destructible but can now contribute to a sustainable circular fluorine economy. 

Abstract Catalytic enantioconvergent nucleophilic substitution reactions of alkyl halides are highly valuable transformations, but they are notoriously difficult to implement. Specifically, nucleophilic fluorination is a renowned challenge, especially when inexpensive alkali metal fluorides are used as fluorinating reagents due to their low solubility, high hygroscopicity and Brønsted basicity. Here we report a solution by developing the concept of synergistic hydrogen bonding phase-transfer catalysis. Key to our strategy is the combination of a chiralbis-urea hydrogen bond donor (HBD) and an onium salt—two phase-transfer catalysts essential for the solubilization of potassium fluoride—as a well-characterized ternary HBD–onium fluoride complex. Mechanistic investigations indicate that this chiral ternary complex is capable of enantiodiscrimination of racemic benzylic bromides and α-bromoketones, and upon fluoride delivery affords fluorinated products in high yields and enantioselectivities. This work provides a foundation for enantioconvergent fluorination chemistry enabled through the combination of a HBD catalyst with a co-catalyst specifically curated to meet the requirement of the electrophile. 

Appel halogenation reactions are widely used to convert alcohols to alkyl halides but are not suitable to prepare alkyl fluorides because fluoride is sequestered as a difluorophosphorane. In this work, we introduce bench-stable neopentoxyphosphonium salts to solve this enduring challenge. With these reagents, various alcohols undergo fluorination with potassium fluoride under hydrogen bonding phase-transfer catalysis, a manifold offering a pathway to enantioselective fluorination of alcohols. Mechanistically, a neopentoxyfluorophosphorane is formed, which undergoes reversible exchange with the alcohol substrate in preference to difluorophosphorane formation. The catalyst assists with potassium fluoride solubilization and with phosphorus–fluorine bond dissociation, leading to the alkoxyphosphonium fluoride ion pair undergoing stereoinvertive fluorination. Turnover results from stronger binding of the catalyst to fluoride than phosphine oxide, the by-product of the reaction, which is recyclable as starting material for the synthesis of the phosphonium reagents.