A series of boronate esters (1–3) and N-heterocyclic carbene (NHC)-stabilized boronate esters (4–6) were synthesized and characterized by various spectroscopic techniques, including NMR (¹H, ¹³C, and ¹¹B), FT-IR, UV-Vis, LC-MS/MS spectrometry, melting point, and elemental analysis techniques. The boronate esters (1–3) and N-heterocyclic carbene (NHC)-stabilized boronate esters (4–6) (as Lewis acid) rapidly catalyze the coupling of a variety of epoxides and CO₂ to obtain cyclic carbonates in the presence of DMAP (as Lewis base) without the organic solvent. Good to excellent yields of various cyclic carbonates were also achieved under suitable conditions (125 °C, 0.5 h, and 1.6 MPa). After seeing the high catalytic performance of boronate ester catalysts, effects of epoxide, base, temperature, CO₂ pressure, reaction time and amount of catalyst and base were investigated for these catalysts. The boronate ester (1) and DMAP showed the best catalytic activity (94.3%) and selectivity (97.5%) for the coupling of CO₂ and ECH under suitable conditions (125 °C, 0.5 h, and 1.6 MPa).

中文翻译：

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硼酸酯与N杂环卡宾（NHC）稳定的硼酸酯的CO2环加成反应的合成及其在环加成反应中的有效催化性能

合成了一系列硼酸酯（1-3）和N-杂环卡宾（NHC）稳定的硼酸酯（4-6），并通过各种光谱技术进行了表征，包括NMR（¹ H，¹³ C和¹¹ B）， FT-IR，UV-Vis，LC-MS / MS光谱，熔点和元素分析技术。硼酸酯（1-3）和N-杂环卡宾（NHC）稳定的硼酸酯（4-6）（路易斯酸）迅速催化多种环氧化物与CO ₂的偶联在没有有机溶剂的情况下，在DMAP（作为路易斯碱）存在下获得环状碳酸酯。在合适的条件下（125°C，0.5 h和1.6 MPa），各种环状碳酸酯的收率也达到了良好或优异的水平。在看到硼酸酯催化剂的高催化性能后，研究了环氧化物，碱，温度，CO ₂压力，反应时间以及催化剂和碱的量的影响。硼酸酯（1）和DMAP在合适的条件下（125°C，0.5 h和1.6 MPa）对CO ₂和ECH偶联显示出最佳的催化活性（94.3％）和选择性（97.5％）。