A new synthesis of 2-nitroindoles

The C-2 lithiation of N-Boc- and N-(phenylsulfonyl)indoles (4–7) followed by reaction with dinitrogen tetroxide at low temperature affords the corresponding 2-nitroindoles 10–13 in 63–78% yields. Deprotection of the N-Boc-2-nitroindoles (10, 11) with trifluoroacetic acid gives 2-nitroindole (3) and 3-methyl-2-nitroindole (14) in essentially quantitative yields.