A Method for Heteroaromatic Nitration Demonstrating Remarkable Thermal Stability

Herein we report a novel heterogeneous pyrrole nitration that can be run on a large scale in batch mode. Activation of sodium nitrate by SO3–pyridine in acetonitrile leads to the formation of an insoluble nitronium sulfate intermediate that effects a high-yielding reaction. These conditions allow for a safer and practical nitration reaction with unique thermal stability that appears to be a function of the low solubility of the proposed nitronium ion carrier. Mechanistic insights gained from reaction kinetics as well as 1H and 15N NMR studies are presented to support this analysis.