The hydrolytic kineticresolution of five glycidaldehyde acetal derivatives was examined using the recombinant Aspergillus nigerepoxide hydrolase as biocatalyst. This could successfully be performed, at room temperature, using solely demineralised water as solvent and following a two-phase methodology allowing us to operate at a global substrate concentration as high as 200 g/L in the reactor. The
使用重组黑曲霉环氧化物水解酶作为生物催化剂检测了五种缩水甘油醛缩醛衍生物的水解动力学拆分。这可以在室温下成功完成,仅使用软化水作为溶剂,并遵循两阶段方法,使我们能够在反应器中以高达200 g / L的总体底物浓度运行。根据缩醛部分的结构,观察到的E值适中至极好,表明仅通过选择正确的取代基就可以非常有效地实现该拆分。因此,未反应的(R)-环氧化物和形成的(S)-二醇都可以良好或优异的ee获得。(对于环氧化物,ee > 99%)。对于最佳的底物,可通过使用约9至10×10 -4 mol%的底物上的生物催化剂对分子的比率在数小时内进行反应。与化学催化剂相比,该酶的周转频率(TOF)和总周转数(TON)被证明是极好的–分别达到6×10 2 mol sub / mol enz / min和6×数量级的值。 10 4 mol sub / mol enz。最佳(两相)反应器的时空产率因此可以达到高达56
A new method for the synthesis of mixed orthoesters from O-allyl acetals
m-methylphenyl) to O-allyl acetals (acroleinacetals: diethyl or cyclic, i.e., 2-vinyl-1,3-dioxanes or dioxolanes). The catalytic systems for these reactions were generated from [RuCl2(PPh3)3] and Na2CO3; [RuCl2(COD)]x} or [OsCl2(1,5-COD)]x}, PPh3, and Na2CO3. Compounds containing an orthoester moiety (dihydroisoxazoles) were prepared via tandem isomerization of O-allyl acetals (to O-vinyl acetals) catalyzed by
提出了两种新的原酸酯和含有原酸酯部分的化合物(二氢异恶唑)的合成方法。通式RC(OR 1)(OR 2)2和RC(OR 1)(OR 2)(OR 3)的混合原酸酯是通过将ROH(R = Bu或m-甲基苯基)加到O-烯丙基缩醛(丙烯醛缩醛:二乙基或环状,即2-乙烯基-1,3-二恶烷或二恶戊环)。这些反应的催化体系是由[RuCl 2(PPh 3)3 ]和Na 2 CO 3生成的。[RuCl 2(COD)] x}或[OsCl 2(1,5-COD)] x },PPh 3和Na 2 CO 3。制备含有原酸酯部分(dihydroisoxazoles)化合物通过的串联异构ø -烯丙基缩醛(以ö -乙烯基缩醛)通过钌络合物,随后环加成到原位生成的2,6- dichlorophenylnitrile氧化物催化。
The first asymmetricchiral N-triflylphosphoramide-catalyzed ionic [2+4] cycloaddition reaction of unsaturated acetals is described. This reaction proceeds through the intermediacy of a vinyl oxocarbenium/chiral anion pair, and the chiral N-triflylphosphoramide anion controls the stereoselectivity of the cycloaddition step. Moderate enantioselectivities (up to 80:20 e.r.) have been obtained when α
Three's a crowd: The combination of a Brønstedacid and a hydrogen‐bond donor cocatalyst was found to promote various ionic [2+4] cycloadditions under mild reaction conditions (see scheme; Ts=4‐toluenesulfonyl). Thiophosphoramides are the most effective cocatalysts because of the stronger counterion activation effect resulting from three, rather than two, hydrogen bonds involved in anion binding.