Photoredox‐Enabled Self‐(3+2) Cyclization of Vinyldiazo Reagents: Synthesis of Cyclopentenyl α‐Diazo Compounds

Abstract

A photocatalytic self‐(3+2) cycloaddition of vinyldiazo compounds is described, which provides cyclopentene derivatives with conservation of one diazo functional group. Experimental insights and density functional theory indicate that the reaction is triggered by an unusual single electron oxidation of vinyldiazo compounds, while the photolysis for the generation of free carbene species is not involved. The synthetic applications of the resulting cyclopentenyl α‐diazo compounds were demonstrated based on the rich chemistry of the diazo functional group.

Visible Light-Induced Reactions of Diazo Compounds and Their Precursors

“…Very recently, Koenigs, Zhou, and co-workers developed a photocatalytic method for the self-cyclization of vinyldiazo compounds 98.1 (Scheme ). This transformation preserves the valuable diazo functional group, allowing for the efficient synthesis of cyclopentenyl α-diazo compounds 98.2 . The reaction mechanism commences with the single-electron oxidation of the vinyldiazo substrate by the photoexcited Ir III complex, yielding a radical cation intermediate.…”

Chiral Magnesium Complex-Catalyzed Asymmetric Cyclization of Vinyl Diazo Compounds with Phenol Derivatives via Noncarbene Pathways

“…These transformations can be roughly categorized into three types (Scheme A bottom). First, due to the resonance nature of vinyl diazo compounds, they often act as dipolar reagents to react with electrophiles to generate diazo cation intermediates Int 1 and Int 2 , which are aligned for tandem electrophilic substitution/addition. − Second, the vinyl diazo compounds can serve as radical acceptors to react with electron-deficient radicals or radical cation species in a photoreaction system, where the vinyl radicals Int 3 are generally formed and could be trapped inter- or intramolecularly . In addition, a variety of cyclic products could be delivered through direct cycloaddition or annulation-rearrangement process, where the vinyl diazo compounds serve as two- or five-atom building units ( Int 4 and 5 ). , Despite these advancements, to the best of our knowledge, the asymmetric transformation of vinyl diazo compounds via noncarbene pathways has not been achieved so far.…”

Photoinduced [3+2] Cycloaddition of Alkyl–Acceptor Diazoalkanes: Diversity-Oriented Synthesis of Pyrazolines Containing a Quaternary Center

“…In addition, diazoalkanes, as ambiphilic reagents, can react with electrophiles to yield diazonium ions or with nucleophiles to yield azo compounds (Figure B) . As such, diazoalkanes serve as practical 1,3-dipoles to react with dipolarophiles for constructing five-membered nitrogen heterocycles. , For example, olefins as dipolarophiles can react with diazoalkanes to assemble pyrazoline rings (Figure C) . This strategy is powerful for the diversity-oriented synthesis of pyrazoline derivatives.…”