Reactions of Piroxicam with Alkyl Iodides.

Alkylation of piroxicam with a homologous series of alkyl iodides gave reversibly formed O-alkyl products 1 as well as unexpected, irreversibly formed zwitterionic compounds 2, alkylated on the pyridine nitrogen, and O,N-bis-alkyl products 3. Proof of structure was accomplished by nmr and X-ray crystal analysis. Product distribution ratios were determined by hplc and are explained by the Hard-Soft Acid-Base principle.