Sulfonic acid-functionalized ordered nanoporous Na~+-montmorillonite (SANM): A novel, efficient and recyclable catalyst for the chemoselective N-Boc protection of amines in solventless media

摘要

Sulfonic acid-functionalized ordered nanoporous Na~+-montmorillonite (SANM) was used as an efficient catalyst for N-tert-butoxycarbonylation of amines with di-tert-butyl dicarbonate under solvent-free conditions at room temperature. Various aliphatic, aromatic, heterocyclic amines and aminols were protected as their corresponding mono-carbamates in excellent yields and short reaction times. No competitive side reactions such as isocyanate, urea, and NJV-di-Boc formation were observed. The reported method is mild, chemoselective and has the advantages such as heterogeneous catalysis, low cost and the recyclability of the catalyst.