Double ortho-C–H Activation/Annulation of Benzamides with Aryl Alkynes: A Route to Double-Helical Polycyclic Heteroaromatics

It
remains a challenge to achieve N,O-double annulations of primary benzamides with aryl alkynes due to
competitive N,N-double annulations.
Herein, we employed sterically hindered 1-methylcyclohexane-1-carboxylic
acid to address this challenge, the double ortho-C–H
activation of benzamides and subsequent N,O-double annulations with aryl alkynes have been accomplished
for the first time. The resulting product can be further transformed
into a double-helical extended π-conjugated polycyclic heteroarene
via Scholl oxidation, which exhibits blue emission with high fluorescence
quantum yields.

鉴于初级苯甲酰胺与芳基乙炔之间N,N-双官能团化反应的竞争性，实现N,O-双官能团化的目标仍是一项挑战。本研究中，我们采用了位阻较大的1-甲基环己烷-1-羧酸以应对此挑战，首次实现了苯甲酰胺的双邻位-C-H激活以及随后的与芳基乙炔的N,O-双官能团化反应。所得产物可通过Scholl氧化进一步转化成双螺旋扩展π共轭的多环杂芳烃，该化合物表现出高荧光量子产率的蓝色发光特性。