Fe-polyaniline composite nanofiber catalyst for chemoselective hydrolysis of oxime

A facile chemoselective one-pot strategy for the deprotection of oxime has been developed using Fe⁰-polyaniline composite nanofiber (Fe⁰-PANI), as a catalyst. Nano material based Fe⁰-PANI catalyst has been synthesized via in-situ polymerization of ANI monomer and followed by reductive deposition of Fe⁰ onto PANI matrix. The catalyst was characterized by FE-SEM, HR-TEM, BET, XRD, ATR-FTIR, XPS and VSM techniques. The scope of the transformation was studied for aryl, alkyl and heteroarylketoxime with excellent chemoselectivity (>99%). Mechanistic investigations suggested the involvement of a cationic intermediate with Fe³⁺ active catalytic species. Substituent effect showed a linear free energy relationship. The activation energy (E_a) was calculated to be 17.46 kJ mol⁻¹ for acetophenone oxime to acetophenone conversion. The recyclability of the catalyst demonstrated up to 10 cycles without any significant loss of efficiency. Based on the preliminary experiments a plausible mechanism has been proposed involving a carbocationic intermediate.