DTBP/TBHP‐Promoted Hydroacylation of Unactivated Alkenes

Abstract

Di-tert-butyl peroxide (DTBP)-promotedi ntermolecular hydroacylation reaction of alkenes with aromatic aldehydes that provides ketonesi sd escribed. In this study,4 -chromanones were formed when 2-(allyloxy)benzaldehydesw ere treated with tert-butyl hydroperoxide (TBHP). The reactions were performed under solvent-and metal-free conditions. Reactions proceeded through the generation of acyl radicals, followed by the reaction with alkenes. Remarkably,n ot only terminal alkenes but also internal alkenes could serve as the starting materials for intramolecular hydroacylationr eaction.Scheme1.Metal-free hydroacylation of alkenes.

Radical Reactions for the Synthesis of 3‐Substituted Chroman‐4‐ones

“…The desired chroman-4-one products 14 were obtained in 31-64 % yields (Scheme 5). [47] Although only moderate yields were observed, the metal-free conditions of this reaction were interesting and attractive for further applications. In the proposed mechanism, an acyl radical intermediate 13a was produced from 13.…”

“…In this study, tert ‐butyl hydroperoxide (TBHP) was employed as the sole oxidant and radical initiator. The desired chroman‐4‐one products 14 were obtained in 31–64 % yields (Scheme ) . Although only moderate yields were observed, the metal‐free conditions of this reaction were interesting and attractive for further applications.…”

Acyl Radical Chemistry via Visible-Light Photoredox Catalysis

“…In this process, a radical species generated from a HAT reagent abstracts the hydrogen atom of aldehydes forming an acyl radical. Common HAT reagents 4b, 17 such as persulfates, 18 or tert- butyl hydro-peroxide, 19 which are used in the traditional thermal radical chemistry, are also applicable to photoredox catalysis. Compounds like quinuclidine 20 and Eosin Y 21 have also emerged as new HAT reagents for activation of aldehydes.…”

Photocatalytic Decarboxylative [3 + 2] and [4 + 2] Annulation of Enynals and γ,σ-Unsaturated N-(Acyloxy)phthalimides by NaI/PPh3 Catalysis

“…Despite the tremendous progress that has been made, there are still some limitations, including the following: (1) expensive photocatalysts or oxidants are essential in these reactions and (2) the hydrolysis process leads to waste generation and a low atomic economy. However, the radical-mediated C–H functionalization of easily available aldehydes is a straightforward and atom-economical way to the synthesis of fused ketones . Zhu and co-workers described an efficient copper-catalyzed annulation of unsaturated α-carbonyl alkyl bromides with enynals, which is the first example of using aldehydes as radical acceptors to afford fused ketones (Scheme b); however, the complex reaction system (including transition-metal catalysts, ligands, additives, and bases) and narrow substrate scope have impeded its further application.…”