Advances in Direct Metal-Catalyzed Functionalization of Azobenzenes

Abstract

Azobenzenes are a unique class of compounds that originally aroused interest because of their exceptional photochromic properties. Selective reactions allowing the preparation of complex polysubstituted azo-based photoswitches, in a direct and efficient manner, have received considerable attention over the past few years. Among them, regio- and chemoselective C–H bond activation in the presence of a transition-metal catalyst has emerged as the most attractive and challenging strategy in the synthesis of sterically constrained azo compounds. This synthetic approach is currently an intensive research field for introducing functional and structural diversity from azobenzenes. This short review summarizes the recent advances in both ortho-functionalization of azobenzenes and the synthesis of azo-derived heterocycles based on transition-metal-catalyzed direct C–H bond activation. The substrate scope, limitation, reaction mechanism as well as additional applications are discussed.

Synthesis of Phenolic Compounds via Palladium Catalyzed C−H Functionalization of Arenes

“…Azoarenes occupy an important place in organic chemistry as well as in material applications as nonlinear optics, dyes, indicators, photochemical switches, and therapeutic agents . Thus, functionalization of azoarene has drawn considerable attention in recent times . The catalytic C−H activation directed by the azo group has proven to be an attractive strategy for the synthesis of functionalized aromatic azo compounds.…”

“…[12] Thus, functionalization of azoareneh as drawn considerable attention in recent times. [13] Thec atalytic CÀHa ctivation directed by the azo group has provent ob ea na ttractive strategy for the synthesis of functionalized aromatic azo compounds. Josephe tal.…”

Ruthenium‐Catalyzed Regioselective Direct Ortho‐Acyloxylation of Azoarenes with Carboxylic Acids via C–H Bond Activation

“…Synthesis of azobenzene derivatives has been investigated in recent years. [10] Palladium-catalyzed ortho-acylation of azobenzenes with α-oxocarboxylic acids, [11] aldehydes, [12] and toluene derivatives [13] have been reported recently. [10] Palladium-catalyzed ortho-acylation of azobenzenes with α-oxocarboxylic acids, [11] aldehydes, [12] and toluene derivatives [13] have been reported recently.…”

“…[9] Direct C-H functionalization of azobenzenes has engrossed significant attention using the azo group as a directing group. [10] Palladium-catalyzed ortho-acylation of azobenzenes with α-oxocarboxylic acids, [11] aldehydes, [12] and toluene derivatives [13] have been reported recently. Wang′s group re-onstrates a broad substrate scope and good functional group tolerance.…”

“…Table 1, entries[8][9][10][11]. The reaction was also monitored with different catalyst loadings, and theTable 1.…”