1,8-diazabicyclo [5.4.0] undec-7-ene: A remarkable base in the epoxidation of α, β-unsaturated-δ-lactones and other enones with anhydrous t-BuOOH
作者:Veejendra K. Yadav、Kamal K. Kapoor
DOI:10.1016/0040-4020(95)00472-k
日期:1995.7
1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) has been studied for the epoxidation of electron deficient alkenes with anhydrous t-BuOOH (TBHP) in dichloroethane. Steric demands are higher than that for alkaline H2O2- DBU is recognised as a remarkablebase in these oxidations as other bases such as triethyl amine, diisopropylethyl amine, and 1,4-diazabicyclo[2.2.2]octane (DABCO) are absolutely inefficient
已经研究了1,8-二氮杂双环[5.4.0]十一碳-7-烯(DBU)在二氯乙烷中用无水t-BuOOH(TBHP)对缺电子的烯烃进行环氧化。立体要求高于对碱性H 2 O 2的要求-在其他氧化中,DBU被认为是一种显着的碱,因为其他碱如三乙胺,二异丙基乙胺和1,4-二氮杂双环[2.2.2]辛烷(DABCO)绝对效率低下。DBU可有效促进α,β-不饱和δ-内酯的氧化,而大多数常规方法要么失败要么表现不佳。
KF adsorbed on alumina effectively promotes the epoxidation of electron deficient alkenes by anhydrous t-BuOOH
作者:Veejendra K. Yadav、Kamal K. Kapoor
DOI:10.1016/0040-4020(95)01026-2
日期:1996.3
KF adsorbed on alumina (KF-Al2O3) has been studied in detail for the epoxidation of electron deficient alkenes with anhydrous t-BuOOH. Aqueous base sensitive functional groups survive the reagent. Cyclopentenones are oxidized in decent to quantitative yields without showing any observable aldol products. α,β,γ,δ-Dienones are regioselectively oxidized at the α,β-position. Unlike aqueous alkaline H2O2
已详细研究了吸附在氧化铝上的KF(KF-Al 2 O 3)用于无水叔丁醇对缺电子烯烃的环氧化。碱敏感的含水官能团在试剂中存活。环戊烯酮被适当地氧化至定量产率,而未显示任何可观察到的醛醇产物。α,β,γ,δ-二烯酮在α,β-位被区域选择性氧化。与碱性H 2 O 2水溶液不同,KF-Al 2 O 3是非立体特异性的,并提供顺式和反式的混合物大多数无环烯酮的氧化物。除了α,β-不饱和内酯的氧化和反应速率的差异外,本试剂通常与t-BuOOH-DBU组合相似。
Asymmetric Synthesis of Furo[3,4‐
<i>b</i>
]indoles by Catalytic [3+2] Cycloaddition of Indoles with Epoxides
A highly efficient N,N′‐dioxide–NiII catalyst system for the catalytic [3+2] cycloaddition of indoles with epoxides through CC cleavage of oxiranes was accomplished under mild conditions. It provided a promising approach for chiral furo[3,4‐b]indoles in up to 98 % yield with up to 91 % enantiomeric excess (ee) and >95:5 diastereomeric ratio (d.r.).
一个高效Ñ,Ñ '二氧化物-镍II为吲哚与环氧化物至C催化的[3 + 2]环加成催化剂体系环氧乙烷的C ^裂解温和的条件下完成的。它为手性呋喃[3,4- b ]吲哚提供了一种有前途的方法,产率高达98%,对映体过量(ee)高达91%,非对映体比率(dr)大于95:5。
Pyrenediones as versatile photocatalysts for oxygenation reactions with <i>in situ</i> generation of hydrogen peroxide under visible light
Pyrenediones (PYDs) are efficient photocatalysts for three oxygenation reactions: epoxidation of electron deficient olefins, oxidative hydroxylation of organoborons, and oxidation of sulfides via in situgeneration of H2O2 under visible light irradiation, using oxygen as a terminal oxidant and IPA as a solvent and a hydrogen donor.
吡咯二酮(PYDs)是用于三种氧化反应的有效光催化剂:缺电子烯烃的环氧化,有机硼的氧化羟基化以及在可见光照射下通过原位生成H 2 O 2,使用氧作为末端氧化剂和IPA作为硫化物的氧化溶剂和氢供体。
Chemo- and regioselective ring-opening of donor–acceptor oxiranes with <i>N</i>-heteroaromatics
The first ring-opening of D–A oxiranes with N-heteroaromatics in a chemoselective C–C bond cleavage manner was achieved. In the presence of 5 mol% of Y(OTf)3 as the catalyst, diverse N-heteroaromatics, including benzotriazoles, purines, substituted benzimidazole, imidazole and pyrazole, reacted well with various D–A oxiranes, providing acyclic nucleoside analogues containing a N-glycosidic bond in