Metal‐free Dehydrogenation of Substituted Cyclohexanones to Phenols

Abstract

The preparation of substituted phenols via a direct carbonyl desaturation is an intrinsic challenging task in modern synthetic chemistry. Herein, we develop a modular catalytic protocol for the synthesis of substituted phenols via the direct dehydrogenative aromatization of simple cyclohexanones in a metal‐free manner. A broad variety of substrates bearing an assortment of functional substituent groups are compatible with this protocol. Preliminary mechanistic investigations revealed that the reaction underwent a hydride leaving mechanism in the presence of a catalytic amount of tetrabutylammonium iodide. The current approach features simple operation, low reagent cost and green conditions. Insight gained from our studies is expected to advance general efforts towards the green synthesis of structurally diverse phenols via readily available raw materials, offering an alternative strategy for the carbonyl desaturation in organic synthesis.

Phenalenyl-Based Photocatalyst for Bioinspired Oxidative Dehydrogenation of N-Heterocycles and Benzyl Alcohols

“…(E)-4-Phenylbut-3-en-2-one (4s). 28 The crude mixture was purified by column chromatography on a silica gel (hexane/EtOAc as an eluent), and product 4s (17 mg, 58% yield) was obtained as a colorless oil. 1 H NMR (500 MHz, CDCl 3 ) δ 7.51 (d, J = 17.4 Hz, 3H), 7.39 (s, 3H), 6.71 (d, J = 16.3 Hz, 1H), 2.38 (s, 3H); 13 C{ 1 H} NMR (126 MHz, CDCl 3 ) δ 198.…”

Synthesis of meta-arylphenol derivatives via acid-promoted rearrangement of cyclohexadienones

“…5 Metal-catalyzed or metal-free dehydrogenative aromatization of 3-arylcyclohexanones or 3-arylcyclohexenones offers an alternative strategy for the synthesis of meta -arylphenol derivatives due to the fact that 3-arylcyclohexanones or 3-arylcyclohexenones are easily accessible compounds (Scheme 1C). 6 For example, in 2013, Kikushima and Nishina reported a CuBr 2 /HBr/O 2 system-promoted synthesis of meta -arylphenols. 7 In 2016, Jiao and co-authors published an I 2 /DMSO system-mediated green conversion of 3-arylcyclohexenones into meta -arylphenols.…”

Copper-Catalyzed Synthesis of Substituted Primary Arylamines from Cyclohexenone Oxime Esters

“…It is surprising that copper catalysis has not yet been developed for the conversion of cyclohexenone oxime esters to primary arylamines. Based on our ongoing efforts in the development of aromatization transformations of cyclohexanone derivatives, we report the Cu-catalyzed synthesis of substituted primary arylamines from cyclohexenone oxime esters (Scheme C).…”