Metavanadate-mediated hydroxyl activation enhances reaction efficiency in the carboxylative cyclization of propargyl alcohol with CO2

Abstract

The catalytic transformation of CO₂ into value-added carbonates, particularly through carboxylative cyclization of propargyl alcohols, has emerged as a prominent research frontier in green catalysis. Herein, we report a hydroxyl activation strategy mediated by metavanadate (VO₃⁻), which significantly enhances the catalytic efficiency of the carboxylative cyclization reaction. Under the optimized conditions (2 mol% AgVO₃/Sphos catalyst, solvent-free, atmospheric CO₂ pressure), up to 96% yields with exclusive chemo-selectivity are obtained within 2 hours. The catalyst exhibits excellent catalytic stability (6 cycles without significant activity loss) and a high turnover number (TON = 1407). Substrate scope studies demonstrate broad applicability, including ethisterone derivatives and propargylamine analogues. Mechanistic insights gained through in situ FT-IR spectroscopy and DFT calculations reveal the key vibrational peaks at 834, 1048, and 1242 cm⁻¹, corresponding to critical intermediates in the hydroxyl activation pathway. The peak intensity evolution during the reaction process provides direct spectroscopic evidence for the proposed activation mechanism and enhanced catalytic performance. This work not only provides fundamental insights into the activation mechanism but also establishes a practical and sustainable approach for CO₂ utilization in organic synthesis.