Synthesis of Phenols from Aryl Ammonium Salts under Mild Conditions

Abstract

A general method for the synthesis of phenols from electron-deficient aryl ammonium salts or heteroaryl ammonium salts under mild conditions was developed. Benzaldehyde oxime, acetohydroxamic acid, and hydroxylamine hydrochloride were investigated as hydroxide surrogates respectively. With these hydroxide surrogates, a series of phenols were prepared in yields of 20–98%.

Hydroxylation of Aryl Sulfonium Salts for Phenol Synthesis under Mild Reaction Conditions

“…Analogously, the reactions proceeded with tolerances to a plethora of important functionalities, such as CN, NO 2 , SO 2 Me, CHO, COR, and COOR. Additionally, aryl sulfonium salts containing electron-donating group in the aryl ring were proven to be inappropriate for the current hydroxylation reaction, which is similar to reports in the literature [ 38 , 39 , 49 , 50 ].…”

“…Recently, the development of alternative electrophiles [ 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 ] as substitutes for conventional aryl halides in hydroxylative reactions have aroused considerable attention in the field of synthetic organic chemistry ( Scheme 1 c) [ 48 , 49 , 50 ]. For instance, Cornella et al have described how pyridinium salts generated in situ from the reaction of aminoheterocycles with pyrylium tetrafluoroborate salts could be converted into their hydroxylated analogue by utilizing acetohydroxamic acid as a hydroxyl source [ 48 ].…”

“…James et al have demonstrated that nitroarenes could also be effectively transformed into phenols via a denitrative functionalization protocol that employs their previously developed pyrrole-based oxime as hydroxylating agent under transition-metal-free conditions [ 49 ]. Cheng and Ye have reported that aryl ammonium salts could also efficiently undergo hydroxylation by using benzaldoxime and acetohydroxamic acid as hydroxide surrogates [ 50 ]. In recent decades, readily accessible and shelf-stable organosulfonium salts have also been proven to be versatile electrophiles for undergoing a broad range of organic transformations [ 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 ].…”

“… Hydroxylation of aryl halides and their counterparts. ( a ) Hydroxylation of aryl halides by using various hydroxide sources [ 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 ]; ( b ) Hydroxylation of aryl halides by using oxime and acetohydroxamic acid [ 34 , 35 , 36 , 37 , 38 , 39 ]; ( c ) Hydroxylation of other aryl electrophiles by using oxime and hydroxamic acid [ 48 , 49 , 50 ]; ( d ) Hydroxylation of aryl sulfonium salts by using oxime and hydroxamic acid (this work). …”

Electrochemically Driven para‐Selective C(sp2)−H Alkylation Enabled by Activation of Alkyl Halides without Sacrificial Anodes

“…For example, the group of Sevov used Ni complexes to implement cross‐electrophile coupling of alkyl and aryl halides and construct multiple alkylarenes under electroreduction conditions [12b–c] . A method for C(sp 2 )−H alkylation through cathodic reduction of alkyl bromides has also recently been proposed [14] . However, the activation of alkyl halides usually requires sacrificial anodes, which often leads to more complex reactions and cumbersome post‐processing.…”