Catalysis Science & Technology COMMUNICATION Cite this: Catal. Sci. Technol., 2017, 7, 2935 Received 10th April 2017, Accepted 19th June 2017 DOI: 10.1039/c7cy00696a rsc.li/catalysis A simple and robust AgI/KOAc catalytic system for the carboxylative assembly of propargyl alcohols and carbon dioxide at atmospheric pressure† Ye Yuan, ab Yu Xie, a Cheng Zeng, b Dandan Song, b Somboon Chaemchuen, a Cheng Chen* a and Francis Verpoort * abcd A simple and robust AgI/KOAc system was developed for the cyclization of propargyl alcohols and carbon dioxide under mild conditions, and was identified to have excellent activities for numerous substrates, especially sterically hindered terminal alkynes and internal alkynes. Notably, the Ag loading involved was an unprecedentedly low level of 0.05 mol%. With the advantages of being nontoxic, abundant, economical and renewable, carbon dioxide (CO 2 ) is considered as a promising substituted C1 source of phosgene and carbon monoxide (CO), and has evoked great interest in the past few decades. 1 However, transformation of CO 2 into high value chemicals remains a great challenge due to the inherent thermodynamic and kinetic stability of CO 2 . 1a Gratifyingly, significant progress has been achieved in this area during the past few decades. 2 Treatment of CO 2 with epoxides, 3 alkynes, 4 alkenes 5 or amines 6 etc. could successively afford the desired products under relatively mild reaction conditions with certain effective catalytic systems. Particularly, one of the most promising and eco-friendly routes of CO 2 utilization is carboxylative cyclization of propargyl alcohols with CO 2 to ac- cess α-alkylidene cyclic carbonates, which are a series of ver- satile heterocyclic compounds with potential bioactivities in pharmaceutical chemistry and wide applications in organic synthesis. 7 In recent years, several successful catalytic processes for the conversion of CO 2 and propargyl alcohols into α-alkylidene cyclic carbonates have emerged. N-heterocyclic carbene/CO 2 adducts, 8 N-heterocyclic olefin/CO 2 adducts, 9 alkoxide-functionalized imidazolium betaines/CO 2 adducts, 10 bicyclic guanidines, 11 phosphines, 12 azole-anion-based apro- tic ionic liquids, 13 etc. have been developed as metal-free cat- alysts for this conversion. However, relatively harsh reaction conditions and high catalyst loadings are usually inevitable for these metal-free catalytic systems. In this regard, transition-metal-based catalytic systems, such as Cu, 14 Ag, 7b,15 Zn, 16 Co, 17 Pd, 18 Ru, 19 and W, 20 have been reported. Among them, Ag-based systems have been of wide interest due to their excellent activation of triple bonds in numerous organic synthesis and catalysis reactions. 21 However, these catalytic systems still suffer from some drawbacks, such as usage of complicated structures, avoid- ance of air, requirement of relatively high catalyst loadings and harsh reaction conditions, and limitations for sterically hindered substrates and internal alkynes. Thus, simple and stable catalytic systems exhibiting robust activities and broad substrate generality under mild conditions are highly desirable. Herein, we reported a simple, economical and highly effi- cient AgI/KOAc catalytic system for the carboxylative assembly of propargyl alcohols with CO 2 to afford α-alkylidene cyclic carbonates. Notably, the reaction could be performed under atmospheric CO 2 using an easily accessible and straightfor- ward procedure even with an extremely low Ag loading of 0.05 mol%. Additionally, the AgI/KOAc system exhibited broad substrate applicability with efficient conversion of sev- eral challenging substrates. The carboxylative cyclization of 2-methylbut-3-yn-2-ol and CO 2 was selected as a model reaction for the screening of the effective catalytic systems (as depicted in Table 1). Initially, different metal compounds were investigated. Interestingly, AgI, KOAc, AgOAc, and KI were demonstrated to be ineffec- tive for the cyclization individually (entries 1–4), whereas α-alkylidene cyclic carbonates were obtained in excellent yields by employing a combination of AgOAc/KI or AgI/KOAc as the catalytic system (entries 5 and 6). In comparison with Catal. Sci. Technol., 2017, 7, 2935–2939 | 2935 This journal is © The Royal Society of Chemistry 2017 a State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, PR China b School of Materials Science and Engineering, Wuhan University of Technology, Wuhan 430070, PR China c National Research Tomsk Polytechnic University, Lenin Avenue 30, Tomsk 634050, Russian Federation d Global Campus Songdo, Ghent University, 119 Songdomunhwa-Ro, Yeonsu-Gu, Incheon, Korea. E-mail: francis.verpoort@ghent.ac.kr † Electronic supplementary information (ESI) available: Materials, instrumenta- tion, procedures, and characterizations. See DOI: 10.1039/c7cy00696a