Tandem synthesis of benzo[b]carbazoles and their photoluminescent properties.

5 H-Benzo[b]carbazoles were prepared through a tandem reaction between 2-ethynyl-N-triphenylphosphoranylidene anilines and α-diazoketones through ketenimine intermediates in moderate-to-good yields. By using this approach, benzo[b]benzo[5,6]indolo[3,2-h]carbazoles, fluoreno[9,1-ab]carbazoles, and fluoreno[9,1-ab]fluoreno[1',9':5,6,7]indolo[3,2-h]carbazoles were constructed in one pot. Moreover, the resulting products emitted light within the range 410-521 nm, with quantum yields of up to 62 %.