A superbase-derived protic ionic liquid (IL, [DBUH][OAc]) catalyst was used to directly synthesize carbamate from an amine, CO₂, and a silicate ester. This IL catalyst was easily prepared using its precursors, DBU, and acetic acid. Using 10 mol% of the catalyst under a CO₂ pressure of 5 MPa in acetonitrile at 150 °C, carbamate was isolated in up to 96% yield. Specifically, aliphatic and aromatic amines were activated even though aromatic amines exhibited low activities because of their low pK_a values. Other functional groups in amines were barely activated, affording exclusive chemoselectivity for amine activation. Isotope labeling experiments indicated that the proton in the counter cation is crucial in the catalytic cycle to produce water. In addition, a chemical shift corresponding to a mixture of aniline and [DBUH][OAc] was observed in the ¹H NMR spectrum, related to the formation of hydrogen bonds between aniline and basic acetate anions. The experimental results indicated that the designed IL catalysts require a protonated cation and a basic anion.

中文翻译：

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使用任务特定的离子液体催化剂从CO ₂直接合成氨基甲酸酯

使用超碱衍生的质子离子液体（IL，[DBUH] [OAc]）催化剂直接从胺，CO ₂和硅酸酯中合成氨基甲酸酯。使用其前体DBU和乙酸可以轻松制备这种IL催化剂。在150°C的乙腈中，在5 MPa的CO ₂压力下，使用10 mol％的催化剂，可分离出氨基甲酸酯，收率高达96％。具体而言，即使芳族胺由于其较低的p K _a而表现出较低的活性，其仍被活化。价值观。胺中的其他官能团几乎未活化，为胺活化提供了唯一的化学选择性。同位素标记实验表明，抗衡阳离子中的质子在产生水的催化循环中至关重要。此外，在¹ H NMR光谱中观察到与苯胺和[DBUH] [OAc]的混合物相对应的化学位移，这与苯胺和碱性乙酸根阴离子之间氢键的形成有关。实验结果表明，设计的IL催化剂需要质子化阳离子和碱性阴离子。