Synthesis of Five-Membered Nitro-Heterocycles

2-Nitropyrroles do not seem to have been made by cyclization procedures, but several such routes have been described for 3-nitropyrroles. The nitro-containing synthon may be of type 1, 2, or 3. In addition, there is one report of the synthesis of a 3,4-dinitropyrrole by direct ring closure. 

Nitromalonaldehyde reacts with ethyl glycinate5-6 and j8-aminopropio-phenone7 in the presence of alkali to yield 6 (66%) and 7 (30%), respectively.5-8 

Quinolinium ylids react similarly to give 3-nitropyrrolo[l,2-a]quinolines (11) (40-45%) and A-phenacylquinoxalinium bromide gives 3-nitro-2-phenylpyrrolo[l,2-a]quinoxaline 12 (41%).J Neither N-acetonyl- nor N-phenacylpyridinium bromide undergoes cyclization with nitromethane. However, when the pyridine ring carries a nitrile group at the 3-position, a 1-nitroindolizine (13) is formed.1 

Russian workers have recently devised a synthesis of 2-anilino-3-nitro-indoles (14) ( 75%) by reacting aromatic amines with trichloronitro-ethylene [Eq. (I)].9 

Condensation of the nitroenamine 15 with glyoxal and glyoxylic acid results in the formation of the pyrrolo[2,l-ft][l,3]thiazine derivatives 16 

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