Nitration in the imidazo[1,2‐a]pyrazine series. Experimental and computational results

Abstract

AbstractNitration was carried out on a series of imidazo[1,2‐a]pyrazine derivatives. The reactivities of diversely substituted derivatives and of all positions of substitution were analysed and experimental results compared with 13‐nmr data and semi empirical calculations (AMI). Although the unsubstituted heterocycle is highly resistant to nitration, electron‐donating groups such as alkoxy or alkylamino on position 8 enhance the reactivity of the imidazo[1,2‐a]pyrazine derivatives towards electrophilic substitution and, more specifically, nitration. The 13‐nmr experiments, electronic distributions and Molecular Electrostatic Potential isodensity surfaces calculated on the neutral forms are in good agreement with experimental results indicating position 3 is the most reactive position towards nitration.