Visible-Light-Driven Dehydrogenative Coupling of Primary Alcohols with Phenols Forming Aryl Carboxylates

Abstract

A preparative method for obtaining aryl esters from aliphatic primary alcohols and phenols was developed. The reaction proceeds under the irradiation of visible light at ambient temperature, dispensing with any oxidant or hydrogen acceptor. Primary alcohols having a variety of functional groups are successfully esterified with phenols. The produced esters can be utilized as the precursor of various carbonyl compounds.

Bromine radical-enhanced HAT activity leading to stoichiometric couplings of methylarenes with acid chlorides

“…Combining the present results and previous reports, 18–21 a plausible mechanism was proposed as shown in Scheme 3. Initially, the irradiation of the Ir III complex would generate a long-lived triple excited *Ir III complex ( τ = 557 ns).…”

Bromine-radical-induced Csp2–H difluoroalkylation of quinoxalinones and hydrazones through visible-light-promoted Csp3–Br bond homolysis

“…Bromine radical as “pioneers of substrate activation” can activate various molecules in organic synthesis, and the resulting intermediates can in turn quench other reactive substrates or intermediates to achieve diverse pivotal chemical transformations, as shown in Scheme 1a. 3–5 The primary way in which bromine radical activates substrates is as an electrophilic hydrogen atom transfer (HAT) 6 agent, abstracting hydrogen atoms from Si–H bonds 3 or C–H bonds 4 to provide nucleophilic silicon or carbon radicals. Taking advantage of this property, we envisioned a radical cross-coupling strategy involving bromine radicals for the visible light-driven homolysis of the C sp 3 –Br bonds (Scheme 1b).…”

Synthetic Applications of Photocatalyzed Halogen‐Radical Mediated Hydrogen Atom Transfer for C−H Bond Functionalization

“…[94] The same group reported also two dehydrogenative strategies based on the generation of bromine radicals for the synthesis of esters by coupling primary alcohols or aldehydes with phenols. [95,96] Recently, a similar approach for the dehydrogenative coupling of aldehydes and alkyl arenes in flow was reported. [97] The use of a photo-flow reactor enabled the authors to shorten the reaction times (from 20 h to 120 min) and increase the productivity up to 10.5 g • day À 1 .…”

“…The same group reported also two dehydrogenative strategies based on the generation of bromine radicals for the synthesis of esters by coupling primary alcohols or aldehydes with phenols [95,96] …”