Reaction of Carboranyl Lithium and 2,3-Dichloroquinoxaline to Synthesize Carborane-Fused N-Heteroaromatic

Nucleophilic substitution of B–H is an important strategy for the synthesis of carborane derivatives. Although the intermolecular B–H nucleophilic substitution has been widely explored, intramolecular B–H nucleophilic substitution has rarely been reported. Herein, we synthesized a novel carborane-fused N-heteroaromatic through a transition-metal-free reaction between carboranyl lithium and 2,3-dichloroquinoxaline. Two intermolecular C–Cl nucleophilic substitutions and one intramolecular B–H nucleophilic substitution with carboranyl lithium were involved in this transformation. Instead of the most electron-deficient B(3)–H vertex, the B–H nucleophilic substitution selectively occurred on the B(4)–H vertex. This method provides a new method for the synthesis of carborane-fused ring compounds.