Copper-catalyzed synthesis of phenol and diaryl ether derivatives via hydroxylation of diaryliodoniums

Abstract

A copper-catalysed hydroxylation of diaryliodoniums to generate phenols and diaryl ethers allows the synthesis of diversely functionalized phenols under mild reaction conditions and prepares diaryl ethers in a one-pot operation.

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

“…or 7 equiv., entries [22][23], reaction time (12 h or 24 h, entries [24][25], equivalents of N-hydroxyacetamide 2a (2 equiv. or 4 equiv., entries [26][27], and the amount of DMSO (4 mL, entry 28), were performed. However, in most cases, variation of the reaction conditions either led to decreased product yield or produced a comparable result to that of entry 21.…”

“…In addition to the classic methods developed in order to access phenols by virtue of Sandmeyer reactions and direct arene oxidation [ 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 ], the transition-metal-catalyzed hydroxylation of aryl halides has also been proven to be one of the most efficient methods by which to synthesize phenol [ 11 , 12 , 13 , 14 , 15 , 16 , 17 ]. A range of hydroxide sources and their surrogates, such as alkali metal hydroxide (MOH) [ 18 , 19 , 20 , 21 ], water [ 22 , 23 , 24 , 25 , 26 , 27 ], boric acid [ 28 ], molecular oxygen [ 29 , 30 ], silanol [ 31 ], hydrogen peroxide [ 31 ], and nitrous oxide [ 32 , 33 ], have been revealed to be effective for the hydroxylation of aryl halides and its variants ( Scheme 1 a). In 2016 and 2017, the group of Fier and Maloney originally disclosed that benzaldoxime [ 34 , 35 , 36 , 37 ] and acetohydroxamic acid [ 38 ] could also function as effective hydroxylating agents for the conversion of aryl halides to phenols ( Scheme 1 b).…”

“… 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). …”

Palladium-Catalyzed Cross-Electrophile Coupling between Aryl Diazonium Salt and Aryl Iodide/Diaryliodonium Salt in H2O–EtOH

“…28 This stoichiometric experiment also supports the ionic pathway rather than radical pathway; i.e., the reaction may proceed through a Pd(0)−Pd(II)−Pd(IV) catalytic cycle (Scheme 3). From diaryliodonium salt, aryl iodide generates as a byproduct 29 which may undergo oxidative addition to Pd(II) species leading to inactive PdI 2 . Ag 2 CO 3 may indirectly prevent the formation of PdI 2 in the reaction.…”