3.5- Diethoxycarbonyl-2,4-dimethylpyrrole

The second group of target molecules selected to illustrate the use of dicarbonyl compounds consists of 3,5-dimethylpyrazole (53), 3-methyl-1-phenylpyrazol-5-one (54) and 3,5-diethoxycarbonyl-2,4-dimethylpyrrole (55). 

An example of the Knorr pyrrole synthesis is provided by the formation of 3,5-diethoxycarbonyl-2,4-dimethylpyrrole (55). Overall ring construction in this case may be related to (46) above. A retrosynthetic analysis involving disconnection of the N—C2 bond, appropriate prototropic shifts, and finally a retro-aldol reaction to effect disconnection of the C3—C4 bond, reveals ethyl acetoacetate and ethyl a-aminoacetoacetate (ethyl 2-amino-3-oxo-butanoate) (56) as reagents. An FGI transform on this latter compound generates the corresponding nitroso (oximino) compound which may also be derived from ethyl acetoacetate. 

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