Non-Noble-Metal Metal–Organic-Framework-Catalyzed Carboxylative Cyclization of Propargylic Amines with Atmospheric Carbon Dioxide under Ambient Conditions

Abstract

The coupling reaction of propargylic amines and carbon dioxide (CO₂) to synthesize 2-oxazolidinones is an important reaction in industrial production, and yet harsh reaction conditions and noble-metal catalysts are often required to achieve high product yields. Herein, one novel noble-metal-free three-dimensional framework, [Mg₃Cu₂I₂(IN)₄(HCOO)₂(DEF)₄]_<i>n</i> (<b>1</b>), assembled by magnesium and copper clusters was synthesized and applied to this reaction. Compound <b>1</b> displays excellent solvent stability. Importantly, <b>1</b>, acting as heterogeneous catalyst, can highly catalyze the cyclization of propargylic amines with CO₂ under atmospheric pressure at room temperature, which can be recycled at least five times without an obvious decrease of the catalytic activity. NMR spectroscopy, coupled with ¹³C-isotope- and deuterium-labeling experiments, clearly clarifies the mechanism of this catalytic system: CO₂ was successfully captured and converted to the product of 2-oxazolidinones, the C≡C bond of propargylic amines can be effectively activated by <b>1</b>, and proton transfer was involved in the reaction process. Density functional theory calculations are further conducted to uncover the reaction path and the crucial role of compound <b>1</b> during the reaction.