Highly Efficient Conversion of Propargylic Alcohols and Propargylic Amines with CO2 Activated by Noble-Metal-Free Catalyst Cu2 O@ZIF-8.

Abstract

The cyclization reactions of propargylic alcohols and propargylic amines with CO2 are important in industrial applications, but it was a great challenge that non-noble-metal catalysts catalyzed both reactions under mild conditions. Herein, the catalyst Cu2 O@ZIF-8 was prepared by encapsulating Cu2 O nanoparticles into robust ZIF-8, and it can effectively catalyze the cyclization of both propargylic alcohols and propargylic amines with CO2 into valuable α-alkylidene cyclic carbonates and oxazolidinones with turnover numbers (TONs) of 12.1 and 19.6, which can be recycled at least five times. The mechanisms were further uncovered by NMR, FTIR, 13 C isotope-labeling experiments and DFT calculations, in which Cu2 O and DBU can synergistically activate the C≡C bond and the hydroxy/amino group of substrates. Importantly, it is the first example of a noble-metal-free catalyst that can catalyze both propargylic alcohols and propargylic amines with CO2 simultaneously.