Additivity rules pyrrole

Approximate additivity rules for the chemical shifts of azoles have been reported (110). For the pyrrole-type nitrogen atoms, the shifts may be related to that of N-Me-pyrrole [25]. They are composed of the algebraical summation of the following contributions ... 

As a rule, such reaction involves splitting of the oxygen-containing radical to give a mixture of simpler pyrroles in low yields. Having no great synthetic value, these results, nevertheless, shed additional light on some peculiarities of this reaction as a whole. 

Monitoring of the addition of unsubstituted pyrrole to benzoylacetylene in methanol (an equimolar ratio of the reagents, room temperature) by ultraviolet (UV) spectroscopy reveals that a band 396 nm) characteristic of the Z-isomer is observed in the initial stage of the reaction [504], Gradually, this band is replaced by another one with 385 nm assigned to E-adducts. Therefore, the Z-isomer is a kinetically controlled product that is in agreement with the rule of trani-nucleophilic addition to acetylenes. 

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