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Immobilization of (L)-valine and (L)-valinol on SBA-15 nanoporous silica and their application as chiral heterogeneous ligands in the Cu-catalyzed asymmetric allylic oxidation of alkenes
New Journal of Chemistry ( IF 3.3 ) Pub Date : 2021-09-03 , DOI: 10.1039/d1nj02580e
Saadi Samadi 1 , Akram Ashouri 1 , Hersh I Rashid 1 , Shiva Majidian 1 , Mahsa Mahramasrar 1
Affiliation  

SBA-15 nanoporous silica was synthesized by hydrothermal method using P123 surfactant and tetraethoxyortosilicate in acidic condition and then functionalized by 3-chloropropyltrimethoxysilane. Next, by immobilization of chiral amino acid (S)-2-amino-3-methyl butanoic acid (L-valine) and chiral amino alcohol (S)-2-amino-3-methylbutane-1-ol (L-valinol), prepared via the reduction of L-valine by NaBH4/I2 in THF, on functionalized-SBA-15, chiral heterogeneous ligands AL*-i-Pr-SBA-15 and AA*-i-Pr-SBA-15 were prepared and characterized by FT-IR, XRD, TGA, EDX, SEM, BET-BJH techniques. The asymmetric allylic oxidation of alkenes was done using copper-complexes of these ligands and the as-synthesized peresters. The reactions were optimized by varying various parameters such as temperature, solvent, amount of chiral heterogeneous ligand, as well as the type and amount of copper salt. Under optimized conditions, 6 mg of AL*-i-Pr-SBA-15 and 3.2 mol% of Cu(CH3CN)4PF6 in acetonitrile at 50 °C, the chiral allylic ester was obtained with 80% yield and 39% enantiomeric excess in 24 h. The recyclability of the chiral heterogeneous catalysts was also evaluated without significant reduction in the reaction results up to three runs.

中文翻译:

(L)-缬氨酸和(L)-缬氨醇在SBA-15纳米多孔二氧化硅上的固定化及其作为手性异质配体在Cu催化烯烃不对称烯丙基氧化中的应用

以P123表面活性剂和原硅酸四乙氧基硅酸盐为原料,采用水热法合成SBA-15纳米多孔二氧化硅,然后用3-氯丙基三甲氧基硅烷进行功能化。接下来,通过固定手性氨基酸(S)-2-氨基-3-甲基丁酸(L-缬氨酸)和手性氨基醇(S)-2-氨基-3-甲基丁烷-1-醇(L-缬氨醇)通过在 THF 中通过 NaBH 4 /I 2还原L-缬氨酸制备,在功能化的 SBA-15 上,手性异质配体 AL*-i-Pr-SBA-15 和 AA*-i-Pr-SBA-15 是通过 FT-IR、XRD、TGA、EDX、SEM、BET-BJH 技术制备和表征。不对称烯丙基ic 烯烃的氧化是使用这些配体的铜配合物和合成的过酸酯完成的。通过改变各种参数如温度、溶剂、手性异质配体的量以及铜盐的类型和量来优化反应。在优化条件下,6 mg AL*-i-Pr-SBA-15 和 3.2 mol% Cu(CH 3 CN) 4 PF 6在 50 °C 的乙腈中,以 80% 的收率和 39 24 小时内对映体过量百分比。还评估了手性非均相催化剂的可回收性,但最多三轮反应结果没有显着降低。
更新日期:2021-09-03
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