The Disappearing Director: The Case of Directed <i>N</i>‐Arylation <i>via</i> a Removable Hydroxyl Group

Abstract

Abstract A facile and broadly applicable method for the regiospecific N ‐arylation of benzotriazoles is reported. Copper‐mediated reactions of diverse 1‐hydroxy‐1 H ‐benzotriazoles with aryl boronic acids lead to 1‐aryl‐1 H ‐benzotriazole 3‐oxides. A N 1‐OH→ N 3 prototropy in the 1‐hydroxy‐1 H ‐benzotriazoles is plausibly the underlying basis, where the tautomer is captured by the boronic acid, leading to C−N (not C−O) bond formation. Because the N−O bond in amine N ‐oxides and 1‐hydroxy‐1 H ‐benzotriazoles can be easily reduced by diboron reagents such as (pinB) 2 and B 2 (OH) 4 , exposure of the 1‐aryl‐1 H ‐benzotriazole 3‐oxides to B 2 (OH) 4 then leads to facile reduction of the N−O bond resulting in diverse, regiospecifically‐arylated benzotriazoles. Thus, the N ‐hydroxyl group in 1‐hydroxy‐1 H ‐benzotriazoles acts as a disposable arylation director. magnified image