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Rational synthesis of interpenetrated 3D covalent organic frameworks for asymmetric photocatalysis
Chemical Science ( IF 7.6 ) Pub Date : 2019/12/19 , DOI: 10.1039/c9sc04882k
Xing Kang 1 , Xiaowei Wu 1 , Xing Han 1 , Chen Yuan 1 , Yan Liu 1 , Yong Cui 1
Affiliation  

Covalent organic frameworks (COFs) show great promise as heterogeneous photocatalysts, but they have not yet been explored for asymmetric photocatalysis, which is important for the sustainable production of pharmaceuticals and fine chemicals. We report here a pair of twofold interpenetrated 3D COFs adopting a rare (3,4)-connected ffc topology for photocatalytic asymmetric reactions by imine condensation of rectangular and trigonal building blocks. Both COFs containing a photoredox triphenylamine moiety are efficient photocatalysts for the cross-dehydrogenative coupling reactions and asymmetric α-alkylation of aldehydes integrated with a chiral imidazolidinone catalyst. Under visible-light irradiation, the targeted chiral products are produced in satisfactory yields with up to 94% enantiomeric excess, which are comparable to those of reported reactions using molecular metal complexes or organic dyes as photosensitizers. Whereas the COFs became amorphous after catalysis, they can be recrystallized through solvent-assisted linker exchange and reused without performance loss. This is the first report utilizing COFs as photocatalysts to promote enantioselective photochemical reactions.

中文翻译:

用于不对称光催化的互穿3D共价有机框架的合理合成

共价有机框架(COF)作为异质光催化剂显示出巨大的前景,但尚未对其用于不对称光催化进行探索,这对于药物和精细化学品的可持续生产非常重要。我们在这里报道了一对双重互穿的 3D COF,采用罕见的 (3,4) 连接的ffc拓扑,通过矩形和三角形构件的亚胺缩合进行光催化不对称反应。两种含有光氧化还原三苯胺部分的 COF 与手性咪唑啉酮催化剂结合,都是有效的光催化剂,可用于醛的交叉脱氢偶联反应和不对称 α-烷基化。在可见光照射下,目标手性产物的产率令人满意,对映体过量高达94%,与报道的使用分子金属配合物或有机染料作为光敏剂的反应相当。虽然 COF 在催化后变成无定形,但它们可以通过溶剂辅助的连接基交换进行重结晶并重复使用,而不会损失性能。这是第一份利用COF作为光催化剂来促进对映选择性光化学反应的报告。
更新日期:2020-02-13
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