Alkene Syn- and Anti-Oxyamination with Malonoyl Peroxides

Preassembly-Controlled Radical Recombination at Bismuth: Decarboxylative C─N Coupling with Sulfonamides

Persistent transition metal radicals form the foundation for many metallaphotoredox protocols. Their ability to efficiently trap organic radicals and convert them into various coupling products has inspired the exploration of selective radical reactions even beyond the d-block. Radical processes involving bismuth hold great potential, but innovative strategies are required to control the reactivity of bismuth intermediates. Herein, we report preassembly as a powerful strategy to enforce a selective recombination of a bismuth(II) radical and an organic radical. As a result, an inner-sphere pathway is accessed, enabling the formation of C─N coupling products.

Phenothiazine Sulfoxides as Active Photocatalysts for the Synthesis of γ-Lactones

N-substituted phenothiazines are prominent and highly effective organic photoredox catalysts, particularly known for their strong reducing capabilities. Despite their wide utility, the closely related phenothiazine sulfoxides, which easily form upon oxidation, have been largely overlooked and have not been explored in the context of photocatalysis. Herein, we describe the discovery and application of N-phenylphenothiazine sulfoxide as a photocatalyst for the reductive activation of cyclic malonyl peroxides, giving access to complex γ-lactones starting from simple olefins. Detailed mechanistic studies were carried out to better understand the in situ formation of the active catalyst species from a commercial precursor, as well as the catalyst species interconversion and the photocatalytic mechanism for the formation of γ-lactone products. Specifically, we employed a broad range of mechanistic tools, including time-resolved spectroscopy, spectroelectrochemistry, transient UV-vis absorption spectroscopy, cyclic voltammetry, isotopic labeling, radical trapping experiments, NMR spectroscopy, and density functional theory (DFT) calculations. The synthetic utility of this protocol is demonstrated in a substrate scope study, highlighting the facile access to complex spirocyclic γ-lactones, which are widely recognized for their biological importance.

Ferric Chloride-Mediated Transacylation of N-Acylsulfonamides

Transacylation of N-acylsulfonamides, which replaces the N-acyl group with a new one, is a challenging and underdeveloped fundamental transformation. Herein, a general method for transacylation of N-acylsulfonamides is presented. The transformation is enabled by coincident catalytic reactivities of FeCl3 for nonhydrolytic deacylation of N-acylsulfonamides and subsequent acylation of the resultant sulfonamides and can be conducted either stepwise or in a one-pot manner. GaCl3 and RuCl3·xH2O are similarly effective for the reaction. This method is mild, efficient, and operationally simple. A variety of functional groups such as halogeno, keto, nitro, cyano, ether, and ester are well tolerated, providing the transacylation products in good to excellent yields.

Iron-Catalyzed Intermolecular Oxyamination of Terminal Alkenes Promoted by HFIP Using Hydroxylamine Derivatives

An atom-economical intermolecular iron-catalyzed oxyamination of alkenes is described herein. The insertion of oxygenated and nitrogenated moieties from the hydroxylamine substrate was observed with full regio- and chemo-selectivity for terminal alkenes in good yields. HFIP as a solvent appeared to have a synergistic effect with the iron catalyst to promote the formation of the oxyaminated products. Preliminary mechanistic studies suggest a pathway going through an aziridination reaction followed by an in situ ring opening.

Organoiodine-Catalyzed Enantioselective Intermolecular Oxyamination of Alkenes

Metal-free, catalytic enantioselective intermolecular oxyamination of alkenes is realized by use of organoiodine(I/III) chemistry. The protocol is applicable toward aryl- and alkyl-substituted alkenes with high enantioselectivity and electronically controlled regioselectivity. The oxyaminated products can be easily deprotected in one step to reveal free amino alcohols in high yields without loss of enantioselectivity. A key to our success is the discovery of a virtually unexplored chemical entity, N-(fluorosulfonyl)carbamate, as a bifunctional N,O-nucleophile.

Beyond osmium: progress in 1,2-amino oxygenation of alkenes, 1,3-dienes, alkynes, and allenes

Olefin 1,2-difunctionalization has emerged as a popular strategy within modern synthetic chemistry for the synthesis of vicinal amino alcohols and derivatives. The advantage of this approach is the single-step simplicity for rapid diversification, feedstock nature of the olefin starting materials, and the possible modularity of the components. Although there is a vast number of possible iterations of 1,2-olefin difunctionalization, 1,2-amino oxygenation is of particular interest due to the prevalence of both oxygen and nitrogen within pharmaceuticals, natural products, agrochemicals, and synthetic ligands. The Sharpless amino hydroxylation provided seminal results in this field and displayed the value in achieving methods of this nature. However, a vast number of new and novel methods have emerged in recent decades. This review provides a comprehensive review of modern advances in accomplishing 1,2-amino oxygenation of alkenes, 1,3-dienes, alkynes, and allenes that move beyond osmium to a range of other transition metals and more modern strategies such as electrochemical, photochemical, and biochemical reactivity.

Recent advances in reactions using diacyl peroxides as sources of O- and C-functional groups

This review summarizes recent advances in reactions utilizing diacyl peroxides as O- and C-sources, with examples illustrating how the reactivity of diacyl peroxides in organic reactions can be controlled.