A three-step sequence has been developed for converting o-nitrobenzald
ehydes into 2-nitroindoles. The key step involves the thermolysis of 2
-(o-azidophenyl)nitroethylene (10) in xylenes which gives 2-nitroindol
e (4) in 54% yield, akin to the classic Sundberg indole synthesis. Thi
s procedure has also been utilized to synthesize 5,6-dimethoxy-2-nitro
indole (14). (C) 1997 Elsevier Science Ltd.