An Efficient Synthesis of Phenols via Oxidative Hydroxylation of Arylboronic Acids Using (NH₄)₂S₂O₈

Abstract

A mild and efficient method for theipso-hydroxylation of arylboronic acids to the corresponding phenols was developed using (NH4)2S2O8as an oxidizing agent. The reactions were performed under metal-, ligand-, and base-free conditions.

Oxidative homocoupling of arylboronic acids catalyzed by a 4‐aminoantipyrine–Pd(II)complex

“…Recently, we studied the ipsohydroxylation of arylboronic acids to the corresponding phenols using (NH 4 ) 2 S 2 O 8 as an oxidizing agent. [19] It is well known that bases have a significant effect on coupling reactions. [20] Thus, we tested the homocoupling reaction of 1a with 0.5 mol% of the 4-AAP-Pd(II) complex and KMnO 4 in the presence of various bases at room temperature.…”

“…Interestingly, when we use (NH 4 ) 2 S 2 O 8 or H 2 O 2 we obtain trace amounts of phenol 3a , which is formed by the oxidative hydroxylation of phenylboronic acid, a side reaction of arylboronic acids occurring in aqueous or alcoholic solvents. Recently, we studied the ipso ‐hydroxylation of arylboronic acids to the corresponding phenols using (NH 4 ) 2 S 2 O 8 as an oxidizing agent …”

Recent Advances in Green Synthesis of Functionalized Phenols from Aromatic Boronic Compounds

“…With (NH 4 ) 2 S 2 O 8 as the oxidant, Celedón and co‐workers reported the efficient synthesis of phenols via oxidative hydroxylation of aryl boronic acids (Scheme b) . The reaction was conducted using microwave‐mediated synthesis and tolerated different kinds of functional groups.…”

Catalyst- and solvent-freeipso-hydroxylation of arylboronic acids to phenols

“…Arylboronic acids are explored as a new source for the synthesis of phenol derivatives due to their easy availability and stability, and the synthetic route is known as the ipso-hydroxylation of arylboronic acids that occurs via C-B bond cleavage. An oxidant, such as O 2 , 8 H 2 O 2 , 9 NaClO 2 , 10 NH 2 OH, 11 (NH 4 ) 2 S 2 O 8 12 N-oxides, 13 is essential for the ipso-hydroxylation reaction (Scheme 1). Catalysts, such as noble metal complexes, 14 transition metal oxides, 9,15 and noble metal catalysts, 16 are oen employed in the reaction system besides a base additive, such as NaOH 17 and NaCO 3 .…”