Alkylpyrroles maleimides

The nitrosation of pyrroles and indoles is not a simple process. The 3-nitroso derivatives (84) obtained from indoles exist largely in oximino forms (85) (80IJC(B)767). Nitrosation of pyrrole or alkylpyrroles may result in ring opening or oxidation of the ring and removal of the alkyl groups. This is illustrated by the formation of the maleimide (86) from 2,3,4 -trime thylpyrrole. 

Nitrosation of pyrrole or alkylpyrroles may result in ring opening or oxidation of the ring and removal of the alkyl groups. This is illustrated by the formation of the maleimide (119) from 2,3,4-trimethylpyrrole. 

With strong oxidizing agents such as chromium trioxide in aqueous sulfuric acid, alkylpyrroles are converted into maleimides, e.g., 154. This oxidative technique played an important part in the classical determination of porphyrin structures. Milder oxidizing agents, such as hydrogen peroxide, convert pyrroles into pyrrolinones, e.g., oxidation of the parent heterocycle gives a tautomeric mixture of pyrrolin-2-ones 155 and 156. 

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