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Direct oxidative carboxylation of terminal olefins to cyclic carbonates by tungstate assisted-tandem catalysis
Green Chemistry ( IF 9.3 ) Pub Date : 2021-09-10 , DOI: 10.1039/d1gc02603h
Roberto Calmanti 1 , Maurizio Selva 1 , Alvise Perosa 1
Affiliation  

Tungstate catalysts are well established for olefin epoxidation reactions, while their catalytic activity for CO2 insertion in epoxides is a more recent discovery. This dual reactivity of tungstate prompted the present development of a catalytic tandem process for the direct conversion of olefins into the corresponding cyclic organic carbonates (COCs). Each of the two steps was studied in the presence of the ammonium tungstate ionic liquid catalyst – [N8,8,8,1]2[WO4] – obtained via a benign procedure starting from ammonium methylcarbonate ionic liquids. The catalytic epoxidation first step was optimised on 1-decene as model substrate, using H2O2 as benign oxidant, [N8,8,8,1]2[WO4] as catalyst and phosphoric acid as promoter affording quantitative conversion with 92% selectivity towards decene oxide. Unfortunately, the addition of CO2 from the start (auto-tandem catalysis) gave low yields of decene carbonate (<10%). On the contrary, the addition of 1 atm CO2 and tetrabutyl ammonium iodide after completion of the epoxidation first step without any intermediate work-up (assisted-tandem catalysis) afforded a 94% yield in decene carbonate. The protocol could be scaled up to a 10 gram scale. The scope of the reaction was demonstrated for primary aliphatic olefins with different alkyl chain lengths (C6–C16), while cyclic and aromatic activated olefins such as cyclohexene and styrene suffered from the formation of undesired overoxidation products in the first step.

中文翻译:

钨酸盐辅助串联催化将末端烯烃直接氧化羧化为环状碳酸酯

钨酸盐催化剂在烯烃环氧化反应中得到很好的证实,而它们对环氧化物中CO 2插入的催化活性是最近的发现。钨酸盐的这种双重反应性促进了目前将烯烃直接转化为相应的环状有机碳酸酯 (COC) 的催化串联工艺的发展。在钨酸铵离子液体催化剂 - [N 8,8,8,1 ] 2 [WO 4 ] -存在下研究了两个步骤中的每一个,该催化剂通过从甲基碳酸铵离子液体开始的良性程序获得。催化环氧化第一步以 1-癸烯为模型底物进行优化,使用 H 2 O 2作为良性氧化剂,[N 8,8,8,1 ] 2 [WO 4 ] 作为催化剂,磷酸作为促进剂,提供定量转化,对氧化癸烯的选择性为 92%。不幸的是,从一开始就加入 CO 2(自动串联催化)导致碳酸癸烯的产率低(<10%)。相反,在环氧化第一步完成后加入1atm CO 2和四丁基碘化铵,无需任何中间后处理(辅助串联催化),碳酸癸烯的产率为94%。该协议可以放大到 10 克的规模。对于具有不同烷基链长度(C 6 -C 16),而环状和芳族活化烯烃如环己烯和苯乙烯在第一步中会形成不希望的过氧化产物。
更新日期:2021-09-22
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