Divergent synthesis of unsymmetrical azobenzenes via Cu-catalyzed C–N coupling

Abstract

An efficient, one-pot, and low-cost metal-catalyzed tandem Chan–Lam coupling/deprotection/oxidation reaction to access unsymmetrical azobenzenes was developed. The phthaloyl group was automatically released from the rest of the molecule under the conditions of the basic catalytic system of this protocol, without extra steps for deprotection. A variety of azobenzenes were easily obtained using this C–N coupling strategy, without precautions against generating undesired azo by-products. Moreover, an unusual, three-component and domino Ullmann/Chan–Lam/deprotection/oxidation reaction proceeded smoothly to assemble azobenzenes in good yields, where phthalic hydrazide served as a source of N2.