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The validity of calculated NMR shifts to predict the outcome of electrophilic aromatic substitution reactions on different heterocyclic compounds has been examined. Based on an analysis of >130 literature examples, it was found that the lowest predicted (13)C and/or (1)H chemical shift of a heterocycle correlates qualitatively with the regiochemical outcome of halogenation reactions in >80% of the investigated cases. In the remaining cases, the site of electrophilic aromatic substitution can be explained by the calculated HOMO orbitals obtained using density functional theory. Using a combination of these two methods, the accuracy increases to >95%.

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Art Winter tweeted this paper by Morten Jrgensen and co-workers last year and I decided to see if semi-empirical methods could help here.  The paper uses Chemdraws chemical shift predictor to predict where a bromine atom will be added to a heteroaromatic...