Scheme 271. Lactam-Fused Carbazole Derivatives^,

Reagents and conditions: (a)⁵⁰⁹ diethyl malonate (3 equiv), diphenyl ether, 250–260 °C, 7 h; (b) NaOH, ethylene glycol, 180 °C, 3 h; (c) P₂O₅, MsOH, 150 °C, 20 min; (d) DMF, reflux, 2 h; (e) bromobenzene, reflux, 3 h; (f)⁵¹⁰ AcOH, reflux, air, 30–40 h.

The chains of atoms in 271.1 that originate from the first and second reacting diethyl malonate molecules are shown in blue and green, respectively.