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General Approach to Silica-Supported Salens and Salophens and Their Use as Catalysts for the Synthesis of Cyclic Carbonates from Epoxides and Carbon Dioxide
The Journal of Organic Chemistry ( IF 3.6 ) Pub Date : 2022-12-01 , DOI: 10.1021/acs.joc.2c02104
Ryan E Barker 1 , Liping Guo 1, 2 , Claudio J A Mota 3, 4, 5 , Michael North 1 , Leonardo P Ozorio 3, 4, 5 , William Pointer 1 , Sarah Walberton 1 , Xiao Wu 1
Affiliation  

General routes for the synthesis of silica-immobilized symmetrical and unsymmetrical salophen and salen ligands and metal complexes have been developed starting from the natural product 4-allylanisole (methyl-chavicol and estragole). The key step of the syntheses is a microwave-assisted, platinum oxide catalyzed hydrosilylation of the terminal alkene of 5-allyl-2-hydroxybenzaldehyde to afford a sol–gel precursor which can be immobilized into silica before or after conversion to salen and salophen ligands to afford unsymmetrical and symmetrical silica-supported ligands, respectively. Both the symmetrical and unsymmetrical silica-supported salophens were found to catalyze the formation of cyclic carbonates from epoxides and carbon dioxide with catalytic activities at least comparable to those previously reported for non-immobilized homogeneous salophens. This reaction could also be carried out in a multi-phase flow reactor using ethyl acetate solutions of 3-phenoxypropylene oxide. Metal complexes of the silica-immobilized ligands could be prepared, and the aluminum complexes were also found to catalyze cyclic carbonate formation.

中文翻译:

二氧化硅负载的 Salens 和 Salophen 的一般方法及其作为催化剂用于从环氧化物和二氧化碳合成环状碳酸酯

从天然产物 4-allylanisole(甲基-chavicol 和 estragole)开始,开发了合成二氧化硅固定的对称和不对称 salophen 和 salen 配体以及金属络合物的一般路线。合成的关键步骤是微波辅助、氧化铂催化的 5-烯丙基-2-羟基苯甲醛末端烯烃的氢化硅烷化,以提供溶胶-凝胶前体,该前体可以在转化为 salen 和 salophen 配体之前或之后固定到二氧化硅中分别提供不对称和对称的二氧化硅支持的配体。发现对称和不对称二氧化硅负载的沙芬均能催化环氧化物和二氧化碳形成环状碳酸酯,其催化活性至少与先前报道的非固定化均相沙芬相当。该反应也可以在多相流反应器中使用 3-苯氧基环氧丙烷的乙酸乙酯溶液进行。可以制备二氧化硅固定配体的金属络合物,并且还发现铝络合物催化环状碳酸酯的形成。
更新日期:2022-12-01
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