Remazol‐Catalyzed Hydroperoxyarylation of Styrenes

Abstract

A mild photocatalytic hydroperoxyarylation of styrenes has been developed, in which a novel photocatalyst, remazol brilliant blue R (RBBR), is employed at low catalytic loading (1 mol %). The operationally easy procedure uses air as the dioxygen source. Simple mono-substituted styrenes react with aryl hydrazines in moderate-to-good yields. RBBR is proposed to act as a photosensitizer for the generation of singlet oxygen.

Thermally Induced Carbohydroxylation of Styrenes with Aryldiazonium Salts

“…Potassium acetate (Table , entries 6–8) was found to be a better suited base than sodium carbonate (Table , entries 1–5), and in the former case the reaction under nitrogen gave a slightly lower yield of alcohol 3 a than that under air (Table , entries 6 and 8). The lower yield obtained under oxygen atmosphere (Table , entry 2) already indicated at an early stage that radical trapping by oxygen is—in contrast to many other carbooxygenations,—at least not the major mechanistic pathway. The use of twice as much alkene 2 a (12 equivalents) did not further increase the yield, as the reaction was then complicated by phase separation (Table , entry 5).…”

“…[4] Seminal examples are the TEMPO/ sodium-mediated carboaminohydroxylationbyStuder et al [5] and the remazol-catalyzed hydroperoxyarylation by Leow et al (Scheme 1). [6][7][8] Inspired by new carboamination reactions, [9] we investigated whether basic conditions-which have so far mainly been applied in Gomberg-Bachmann reactions [1e, 10, 11] -could also add to the attractiveness of Meerwein-type carbohydroxylations.…”

Recent Advances in Meerwein Arylation Chemistry

“…Scheme 13 Hydroperoxyarylation of alkenes using oxygen from air 33,60 An unusual photocatalyzed carbooxygenation, as developed by Leow, 61 is depicted in Scheme 14. The activated photocatalyst Remazol brilliant blue R (RBBR) promotes the oxidation of phenylhydrazine (29) to phenyldiazene (PhN=NH).…”

Photochemical and electrochemical C–N borylation of arylhydrazines

“…Photochemistry 9–13 and electrochemistry 14–20 represent two environmentally benign strategies in organic synthesis. Arylhydrazines were reported to generate aryl radical species upon visible light irradiation 21–29 or anodic oxidation. 30 Recently, borylation reactions based on a radical mechanism have attracted considerable attention.…”