Transition Metal‐Free ipso‐Functionalization of Arylboronic Acids and Derivatives

Abstract

Arylboronic acids and their derivatives have been widely exploited as important synthetic precursors in organic synthesis, materials science, and pharmaceutical development. In addition to numerous applications in transition-metal-mediated cross-coupling reactions, transition-metal-free transformations involving arylboronic acids and derivatives have recently received a surge of attention for converting the C-B bond to C-C, C-N, C-O, and many other C-X bonds. Consequently, a wide range of useful compounds, e.g., phenols, anilines, nitroarenes, and haloarenes, have been readily synthesized. Amongst these efforts, many versatile reagents have been developed and a lot of practical approaches demonstrated. The research in this promising field is summarized in the current review and organized on the basis of the type of bonds being formed.

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

“…In organoboronic acids, the boron atoms adopt sp 2 hybridization. 16 As shown in Fig. 4, when Consequently, the target product P is released with 104.1 kcal mol À1 relative to the zero-point surface of exergonicity.…”

“…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 . 18 Moreover, some organic solvents, such as CH 3 OH, 19 CH 3 CH 2 OH, 18 CHCl 3 , 20 DMF, 21 THF, 22 are used as the reaction solvents.…”

Ascorbic Acid as a Highly Efficient Organocatalyst for ipso‐Hydroxylation of Arylboronic Acid

“…Many literatures have been reported for the ipso ‐hydroxylation of arylboronic acid utilising transition metal based catalytic systems such as CuSO 4 ‐Phenanthroline, CuNP, CuFe 2 O 4 , Montmorilonite‐KSF entrapped Cu(OH) x , H 2 O 2 ‐Cu 3 (BTC) 2 , H 2 O 2 ‐Cu 2 O NP etc. Some metal free procedures have also been reported using H 2 O 2 ‐complexes,, TBHP, oxone,, m ‐CPBA, NH 2 OH, H 2 O 2 ‐Amberlite IR‐120, H 2 O 2 ‐Acidic Al 2 O 3 , H 2 O 2 ‐H 3 BO 3 , H 2 O 2 ‐Lactic acid, H 2 O 2 ‐biosilica, quinone, etc. Most of the reported methods have some shortcomings such as use of excess oxidizing agent, higher temperature, base, metal catalysts etc.…”

Metal‐Free Cross‐Coupling of Arylboronic Acids and Derivatives with DAST‐Type Reagents for Direct Access to Diverse Aromatic Sulfinamides and Sulfonamides

“…[11] Both transition-metal-catalyzed and metal-free transformations of arylboronic acids have been studied extensively. [12,13] We therefore envisaged that ametalfree sulfonation of arylboronic acids might be possible with as uitable reagent. This kind of reagent should be able to activate the boronic acid, and it should contain af unctional group that has an À SO 2 À moiety or afunctionality that can be readily converted into as ulfonyl group.T oo ur delight, this idea was realized when DAST was chosen as the reagent and sulfinamide 3aa was obtained.…”