Some Notable Syntheses of Pyrroles

This synthesis of octaethylporphyrin, widely used as a model compound, uses a Barton-Zard sequence and leads to a pyrrole-2-ester which is then hydrolysed and decarboxylated. 

All of the non-natural isomers (porphycenes) of the porphyrin ring system comprising permutations of four pyrrole rings, four methines and having an 18 Jt-electron main conjugation pathway, have been synthesised. The scheme below shows the use of a MacDonald condensation to assemble a tetrapyrrole and then the use of the McMurray reaction to construct the macrocycle.  

Several ingenious approaches have been described for the elaboration of the pyrrolo-indole unit (strictly a benzo[l,2-fc 4,3-( ]dipyrrole) three of which are present in the potent anti-tumour compound CC-lObS the approach shown here uses the van Leusen approach (16.16.1.3). ° 

Two isomeric mono-nitro derivatives, C5H6N2O2, are formed in a ratio of 6 1, by treating 2-methylpyr-role with AC2O/HNO3. What are their structures and which would you predict to be the major product  

Write structures for the products formed by the reaction of pyrrole with POCI3 in combination with  

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