氨基酸DES催化3-苯基环丁酮的不对称Baeyer-Villiger氧化反应

Asymmetric Baeyer-Villiger Oxidation of Pheny lcyclobutanone Catalyzed by Amino Acid DES

以手性氨基酸与Br?nsted酸为原料合成了一系列新型酸性低共熔溶剂(DES)催化剂,以环境友好的H2O2为氧化剂,首次将DES应用于环酮的不对称Baeyer-Villiger氧化反应中。以3-苯基环丁酮为模板底物,探究了不同DES的催化活性,其中以L-亮氨酸(L-Leu)为氢键受体(HBA)、以H3PO4为氢键供体(HBD)合成的DES为最优催化剂。研究了HBA与HBD的比例、催化剂用量、氧化剂用量、反应温度、反应时间等对催化反应的影响。较佳条件:n(HBD)∶n(HBA)=4∶1,n(DES)∶n(H2O2)∶n(底物)=2.6∶7∶1,反应温度25℃,反应时间5 h。较佳条件下,苯基环丁酮转化率98.59%,苯基丁内酯产率78.08%,对映体过量百分数69.26%。水相中的DES经过干燥后可以重复使用,经过6次循环使用后催化活性有些许下降(DES在每次分离时有少量损失所致)。DES催化剂L-Leu/4H3PO4还可以用于其它环酮底物的B-V氧化反应,结果表明该催化剂具有较好的底物普适性。

A series of new acidic DES catalysts were synthesized from chiral amino acids and Bronsted acids.Using eco-friendly H2O2 as oxidant,DES catalysts were applied to the asym-metric Baeyer-Villiger catalytic oxidation of cyclobutanones.Using 3-phenylcyclobutanone as.template,the catalytic activities of different DESs were investigated,and the best catalyst was DES synthesized with L-Leu as hydrogen bond receptor(HBA)and H:PO4 as hydrogen bond donor(HBD).The effects of the ratio of HBA to HBD,catalyst amount,oxidant dose,reaction temperature,and reaction time on the reaction were studied.The optimum conditions are:n(HBD):n(HBA)=4:1,n(DES):n(H2O2):n(substrate)=2.6:7:1,reaction temperature 25 C,and reaction time 5 h.Under the optimum conditions,the conversion of phenyleyclobutanone is 98.59%,the yield of phenylbutyrolactone is 78.08%,and ee is 69.26%.DES in aqueous phase can be reused after drying,and the catalytic activity decreases slightly after 6 cycles(due to a small loss of DES at each separation).DES catalyst L-Leu/4H3PO4 can also be used for B-V oxidation of other cycloketone substrates,and the results show that DES has good substrate universality.