Coupling reactions of amines and alcohols are of central importance for applications in chemistry and biology. These transformations typically involve the use of a reagent, activated as an electrophile, onto which nucleophile coupling results in the formation of a carbon-nitrogen or a carbon–oxygen bond. Several promising reagents and procedures have been developed to achieve these bond forming processes in high yields with excellent stereocontrol, but few offer direct coupling without the intervention of a catalyst. Herein, we report the synthesis of chiral donor–acceptor azetines by highly enantioselective [3 + 1]-cycloaddition of enoldiazoacetates with aza-ylides and their selective coupling with nitrogen and oxygen nucleophiles via 3-azetidinones to form amino acid derivatives, including those of peptides and natural products. The overall process is general for a broad spectrum of nucleophiles, has a high degree of electronic and steric selectivity, and retains the enantiopurity of the original azetine.

Based on the strategy of polarity reversal in the generation of free radicals derived from diazo compounds, photocatalyzed multicomponent reactions (MCRs) of nitrogen aromatic heterocycles, alkenes, and diazo compounds form functionalized derivatives in good to high yields and exacting regioselectivities. The carbon radicals generated from the acceptor diazo compounds are electrophilic, and their selective additions with alkenes provide nucleophilic radicals, which enable the further rapid assembly with various heteroarenes. A delicate balance has been achieved between the activation of heteroarenes through protonation and the decomposition of diazo compounds by the same acid. This multicomponent Minisci reaction shows high functional group tolerance, especially in the incorporation of biologically active molecules. Detailed mechanistic studies that include photophysical measurements elaborate this radical cascade reaction. Furthermore, this transformation provides new opportunities for versatile reactions of diazo compounds in radical cascade multicomponent coupling reactions.

1,2,3-Triazine 1-oxides are formed by nitrosyl addition from tert-butyl nitrite to the vinylogous position of vinyl diazo compounds. This transformation, which is a formal intermolecular [5 + 1] cycloaddition, occurs under mild conditions, with high functional group tolerance and regioselectivity, and can be employed for late-stage functionalization. Upon heating at refluxing chlorobenzene temperature, these triazine-N-oxides undergo dinitrogen extrusion to form isoxazoles in very high yields.

Oxidative cleavage reactions of arylalkenes by tert-butyl hydroperoxide that occur by free radical processes provide access to carboxylic acid or ketone products. However, the pathway to these cleavage products is complex, initiated by regioselective oxygen radical addition to the carbon–carbon double bond. Subsequent reactions of the initially formed benzyl radical lead eventually to carbon–carbon cleavage. Thorough investigations of these reactions have identified numerous reaction intermediates that are on the pathways to final product formation, and they have identified a new synthetic methodology for the synthesis of peroxy radical addition-induced hydroperoxide formation.

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