Cyclofunctionalisation of epoxyalcohol derivatives. 1. Delivery of functionalised carbon for stereospecific synthesis of dihydrofurans and dihydroxyacids
作者:Stuart W. McCombie、Bandarpalle B. Shankar、Ashit K. Ganguly
DOI:10.1016/s0040-4039(01)84583-4
日期:——
E-2-(Phenylsulfonyl)vinyl ethers of 2,3-epoxyalcohols are stereospecifically rearranged to 3-(phenylsulfony])-4-(1-hydroxyalkyl)-4,5-dihydrofurans on treatment with LDA. Oxidation of these compounds or the derived des-sulfonyl compounds provides esters or lactones which correspond to regiospecific delivery of -CO2H or -CH2CO2H to C-2, with inversion.
在用LDA处理后,将2,3-环氧醇的E-2-(苯磺酰基)乙烯基醚立体有择地重排为3-(苯磺酰基)-4-(1-羟烷基)-4,5-二氢呋喃。这些化合物或衍生的去磺酰基化合物的氧化提供了酯或内酯,其对应于-CO 2 H或-CH 2 CO 2 H向C-2的区域特异性递送,并具有转化作用。
Manganese-Catalyzed Epoxidations of Alkenes in Bicarbonate Solutions
作者:Benjamin S. Lane、Matthew Vogt、Victoria J. DeRose、Kevin Burgess
DOI:10.1021/ja025956j
日期:2002.10.1
screening, for the epoxidation of alkenes. It useshydrogenperoxide as the terminal oxidant, is promoted by catalytic amounts (1.0-0.1 mol %) of manganese(2+) salts, and must be performed using at least catalytic amounts of bicarbonate buffer. Peroxymonocarbonate, HCO(4)(-), forms in the reaction, but without manganese, minimal epoxidation activity is observed in the solvents used for this research
total synthesis of myxol stereoisomers 1a,b and deoxymyxol (plectaniaxanthin) stereoisomers 2a,b was accomplished by Wittig reaction of (S)- and (R)-C10-phosphonium salts 8a,b bearing a silyl-protected 1,2-dihydroxy-ψ end group with C30-apocarotenals 6 and 7. The phosphonium salts 8a,b were derived from aldehydes 11a,b possessing a cyclopentylidene ketal moiety, prepared via Sharpless asymmetric epoxidation
underwent structural transformation in the presence of H2O2 but regenerated to their initial state at the end of the reaction. In particular, the highly dispersed Nb oxoclusters can absorb a large amount of polar organic solvents and thus were swollen greatly, which exhibited “pseudo” liquid phase behavior, and enabled the substrate molecules to be highly accessible to the catalytic center of Nb oxocluster
我们在这里提出了一种新型的铌氧簇,它可以通过羧酸盐离子液体有效地稳定下来。这些功能化的IL在本工作中分别命名为[TBA] [LA],[TBA] [PA]和[TBA] [HPA],其中TBA代表四丁基铵,LA,PA和HPA分别指乳酸,丙酸酯,3 -羟基丙酸酯阴离子。已通过元素分析,NMR,IR,XRD,TGA和HRTEM对合成的Nb氧簇进行了表征。发现[TBA] [LA]稳定的Nb氧簇(Nb-OC @ [TBA] [LA])均匀分散,平均粒径为2-3 nm,并具有极高的催化活性,可选择性氧化各种硫醚。在催化剂负载量低至0.0033 mol%(1 ppm)时,Nb-OC @ [TBA] [LA]催化剂的周转数超过56000。与此同时,通过仅使用0.065mol%的催化剂(50ppm),该催化剂还显示出对烯烃和烯丙基醇的环氧化的高活性。的表征93 Nb NMR光谱表明,Nb氧簇在H 2 O 2存
A Cheap, Catalytic, Scalable, and Environmentally Benign Method for Alkene Epoxidations
作者:Benjamin S. Lane、Kevin Burgess
DOI:10.1021/ja004000a
日期:2001.3.1
aliphatic alkenes can be selectively epoxidized in the presence of terminal alkenes. This experiment also implies that the allylic hydroxyl does not activate the terminal alkene via a directing effect. Entries 9-12 illustrate that epoxidations of arylsubstituted alkenes proceed smoothly; qualitatively, the rates of these reactions were observed to be appreciably faster than for aliphatic alkenes. The only
烯烃环氧化的良性方法 Benjamin S. Lane 和 Kevin Burgess* 德克萨斯 A & M 大学化学系 PO Box 30012, College Station, Texas 77842-3012 收到 2000 年 11 月 17 日 本文报告了一种简单的方法,其中锰 (2+)盐,例如 MnSO4,使用 30% 的过氧化氢水溶液作为末端氧化剂催化烯烃的环氧化。通过将底物和催化剂溶解在 DMF 或叔丁醇中,然后缓慢加入 30% 过氧化氢和 0.2 M 碳酸氢钠缓冲液的混合物来进行反应。这种方法在成本、简单性和环境因素方面有几个理想的属性。该项目来自在筛选新的、手性的、1,4、7-三氮杂环壬烷 (TACN) 配合物作为潜在的不对称环氧化催化剂。在一个简单的平板装置 1 中的高通量筛选表明,没有任何有机配体的简单锰 (2+) 盐介导了环氧化,但仅在碳酸氢盐缓冲液中。在基于