Pro‐aromaticity Enabled Dealkenylative Functionalizations via Photo‐Excitation and Oxidation

Abstract

A general and practical approach for diverse dealkenylative functionalization of olefin‐containing substrates has been developed through the one‐pot formation and utilization of pro‐aromatic 1,4‐dihydropyridazines using tetrazine as the key cycloaddition reagent. Triggered by either excitation or oxidation, the targeted C−C bonds in the 1,4‐dihydropyridazine intermediates could be readily cleaved to generate alkyl radicals for subsequent transformations. Diverse carbon‐carbon and carbon‐hetero bond forming protocols, including Giese‐type addition, hydrazination, borylation, Minisci‐type alkylation, copper‐catalyzed NH alkylation, acylation, alkynylation, cyanation, and azidation, are achieved in a highly modular fashion.

Aromatization-driven deconstructive functionalization of spiro dihydroquinazolinones via dual photoredox/nickel catalysis

“… 8 Especially in radical chemistry, the aromatization-driven cleavage of chemical bonds is an important transformation. In this field, structurally diverse pre-aromatic (PA) compounds such as 1,4-DHPs, 9 benzothiazolines, 10 dihydroquinazolinones, 11 and others 12 are widely used as hydrogen atom transfer (HAT) reagents, functional group transfer reagents and radical precursors. For example, Dong and co-workers disclosed several unique deacylative C–C bond functionalizations of chain ketones, 13 in which the in situ formed pre-aromatic intermediates underwent Ir( iii )-catalyzed aromatization-driven C–C bond cleavage to achieve the deacetylation process.…”

C(sp3)–C(sp3) Radical-Cross-Coupling Reaction via Photoexcitation

“…However, structurally similar alkyl-DHPs were recently been utilized by the Tang group as a precursor for “transfer-alkylation” reactions for the construction of C–C bonds (Scheme b) . Later, Nishibayashi, Sakata, Molander, and other groups used alkyl-DHPs for an alkyl-transfer process (Scheme c) . Very recently, the Melchiorre group successfully implemented alkyl-DHPs as a powerful reductant in their excited state for single-electron transfer (SET) in the presence of a suitable acceptor to construct various C–C bond formations, without the requirement of any external photocatalysts (Scheme d) …”