Ochoa-Gómez José R, Lorenzo-Ibarreta Leire, Diñeiro-García Cristina, Gómez-Jiménez-Aberasturi Olga
TECNALIA, Basque Research and Technology Alliance (BRTA), Parque Tecnológico de Alava Leonardo Da Vinci 11 01510 Miñano (Alava) Spain
RSC Adv. 2020 May 18;10(32):18728-18739. doi: 10.1039/d0ra03552a. eCollection 2020 May 14.
Isosorbide bis(methyl carbonate) (IBMC) is a scarcely studied green chemical with potential applications in the manufacturing of non-isocyanate polyurethanes and bisphenol A-free polycarbonates. Its synthesis by transesterification of isosorbide with dimethyl carbonate (DMC) is very negatively influenced by the presence of small amounts of acidic impurities in isosorbide when heterogeneous inorganic carbonates such as potassium and cesium carbonates are used as catalysts. In this paper it is shown that the problem can be solved by using homogeneous catalysts consisting of nitrogenated bases and superbases having a suitable dual nucleophilic-basic character and able to form a highly reactive acyl intermediate with the electrophilic reactant DMC. Cycloaliphatic secondary and tertiary amines, guanidines and amidines covering a nucleophilicity parameter () range between 13.58 and 20.58 in either acetonitrile or dichloromethane, and a p range in acetonitrile between 15.68 and 26.02 have been tested in batchwise mode. Highly active catalysts leading to hydroxyl conversions of 84-93% require a minimum of 16 and a p ranging from 18.0 to 26.0. Within this p range, must increase by about 0.5-0.6 units per each unit the p falls to keep the catalytic activity, indicating that nucleophilicity has approximately twice as much influence as basicity on the catalytic activity. One guanidine (TBD), one amidine (DBN) and three cycloaliphatic secondary amines (-methylpyrrolidine, quinuclidine and DABCO) have been found to be excellent catalysts at 5 mol% ISO. The side reaction leading to oligomer formation is not avoided, with oligomers, mainly the dimer, affording 6 wt% of the crude product independently of hydroxyl-conversion and catalyst type.
异山梨醇双（碳酸甲酯）（IBMC）是一种研究较少的绿色化学品，在非异氰酸酯聚氨酯和无双酚A聚碳酸酯的制造中具有潜在应用。当使用碳酸钾和碳酸铯等非均相无机碳酸盐作为催化剂时，异山梨醇与碳酸二甲酯（DMC）通过酯交换反应合成IBMC会受到异山梨醇中少量酸性杂质的严重负面影响。本文表明，使用由具有合适双亲核 - 碱性特征且能够与亲电反应物DMC形成高活性酰基中间体的含氮碱和超强碱组成的均相催化剂可以解决该问题。在乙腈或二氯甲烷中亲核性参数（）范围为13.58至20.58且在乙腈中p范围为15.68至26.02的脂环族仲胺、叔胺、胍和脒已以间歇模式进行了测试。导致羟基转化率达到84 - 93%的高活性催化剂需要最小为16且p范围为18.0至26.0。在该p范围内，每降低一个单位的p，必须增加约0.5 - 0.6个单位以保持催化活性，这表明亲核性对催化活性的影响约为碱性的两倍。已发现一种胍（TBD）、一种脒（DBN）和三种脂环族仲胺（ - 甲基吡咯烷、奎宁环和三乙烯二胺）在ISO为5 mol%时是优异的催化剂。导致低聚物形成的副反应无法避免，低聚物主要是二聚体，无论羟基转化率和催化剂类型如何，其在粗产物中的含量均为6 wt%。
