Hypothesis, heterocyclic compound formation

The high selectivity in the a positions which is illustrated in the formation of compounds 49 and 50 has been tentatively explained50 by a homolytic hydroxylation, a process well known for phenols50 and also for other heterocyclic compounds.60 This hypothesis is supported by studies on oxidation of unsubstituted pyrrole with hydrogen peroxide in conditions suitable for the generation of hydroxy radicals heating, light, or ferrous ions.50... 

The hypothesis about the formation of compounds like B was also proven by other authors [35, 36]. For example, the Padmavathi et al. [36] studied the reactions of heterocyclic analogues of chalcones 14 obtained from the appropriate diaroylacetones 13 and diazomethane (Scheme 2.5). It was shown that this treatment gives a solid which was identified as (4 -aryl-4/,5 -dihydro-l/Ff-pyrazol-3 -yl)-(4-aryl-l/f-pyrrol-3-yl)methanone 15. 

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