Visible light-mediated photo-oxygenation of arylcyclohexenes

Abstract

The photo-oxygenation of versatile arylcycloalkenes proceeds through zwitterionic intermediates and provides access to new allyl hydroperoxides and endoperoxides.

Light‐Driven Waste‐To‐Value Upcycling: Bio‐Based Polyols and Polyurethanes from the Photo‐Oxygenation of Cardanols

“…The high efficacy of such downstream diversifications has been demonstrated with cardanol monoene‐derived product mixtures. A saturated aqueous solution of inexpensive sodium sulfite (Na 2 SO 3 ) [20] effected clean reduction of the crude product solution of the cardanol monoene hydroperoxides (without any workup) to give full conversion (Scheme 3 a). The resultant two regioisomeric allyl alcohol derivatives were isolated in overall 79 % yield (two distinct sets of 13 C NMR signals).…”

“…The CH oxidation of allylic hydrocarbon positions with singlet oxygen is an especially useful reaction that operates under very mild conditions with perfect atom economy by incorporation of both oxygen atoms from 1 O 2 [17,18] . The resultant allylhydroperoxides are versatile intermediates that can be readily converted to various oxygenates including alcohols, ketones, and epoxy alcohols [19–21] . High dispersions of the three distinct entities – gas (O 2 ), light, and solution phase – may be challenging so that mass transfer across phase boundaries and light penetration depth may become rate‐determining.…”

“…[ 17 , 18 ] The resultant allylhydroperoxides are versatile intermediates that can be readily converted to various oxygenates including alcohols, ketones, and epoxy alcohols. [ 19 , 20 , 21 ] High dispersions of the three distinct entities – gas (O 2 ), light, and solution phase – may be challenging so that mass transfer across phase boundaries and light penetration depth may become rate‐determining. Several microreactor setups have been developed to overcome this limitation, such as film, [22] microchannel, [23] or tube reactors.…”

Selective C–H Allylic Oxygenation of Cycloalkenes and Terpenoids Photosensitized by [Cu(Xantphos)(neoc)]BF4

“…Beyond the technical multiton scale productions of natural products, i.e., the fragrance Rose oxide and the antimalarial drug Artemisinin, − singlet oxygen “ene” reaction is still underutilized in the context of the oxyfunctionalization processes. Herein, we present, for the first time, the regioselective oxygenation of several substituted cycloalkenes − and terpenoids performed by 1 O 2 generated in situ upon UV–vis light irradiation of the noble-metal-free Xantphos/neocuproine/diimine copper-complex [Cu­(Xantphos)­(neoc)]­BF 4 Cu-1 under atmospheric conditions (Scheme C), a procedure that may open new research avenues in copper-photosensitized oxygenation processes.…”

Visible-Light Photoredox Catalyzed Dehydrogenative Synthesis of Allylic Carboxylates from Styrenes

“…At the outset of the optimization stage, we discovered that the combined use of [Co(III)(dmgH) 2 pyCl] ( 3a ) (5 mol %, dmgH = dimethylglyoximate, py = pyridine) and Fukuzumi 9-mesityl-10-methylacridinium perchlorate ( 4a ) (2.5 mol %) promoted the chemoselective anti -Markovnikov ( 5aa vs 5aa″ ) 5a , 11 , 12 formation of the butyrate 5aa in 63% yield (blue LED 23 W 465 nm, rt, DCM, entry 1, Table 1 ). Furthermore, high allylic ester ( 5aa ) vs enolester ( 5aa′ ) chemoselectivity (generally >25:1) was observed as well (see mechanistic discussion for details).…”