Novel CuBr·SMe2Catalyzed Conjugate Addition of 3-Trimethylsilyl-1-propenylzirconocene to Divinylketones. Stereoselective Synthesis of Polysubstituted Cyclohexanones
Ruthenium-catalyzed allylation of primary alcohols by allylic acetates: a novel synthesis of .alpha.,.beta.-unsaturated ketones
摘要:
Certain ruthenium complexes show high catalytic activity in the synthesis of alpha,beta-unsaturated ketones from primary alcohols and allylic acetates. Here, pi-allylruthenium intermediates apparently operate as nucleophiles rather than as electrophiles.Among the carbon-carbon bond forming reactions promoted by transition-metal complexes, allylic alkylations, especially those catalyzed by palladium complexes, have been extensively studied and have been successfully applied in organic synthesis.1 In contrast, comparatively little is known about alkylation reactions involving pi-allylruthenium intermediates, despite the current interest in the synthesis of pi-allylruthenium complexes.2In the course of studies of catalysis by ruthenium complexes,3 we found that pi-allylruthenium intermediates act as nucleophiles rather than as electrophiles in reactions with aldehydes to give homoallylic alcohols.4 This reactivity is quite different from that of pi-allylpalladium complexes which generally act as electrophiles.5 Because many biologically important natural products possess an enone functionality, and because the synthesis of such compounds has been the target of much effort over the last decade,6 we attempted to apply ruthenium catalysis to the synthesis of enones. Therefore, in this paper, we describe a novel synthesis of alpha,beta-unsaturated ketones from primary alcohols and allylic acetates via pi-allylruthenium intermediates (eq 1).
Catalytic asymmetric allylations of achiral and chiral aldehydes via BINOL–Zr complex
作者:Michio Kurosu、Miguel Lorca
DOI:10.1016/s0040-4039(02)00139-9
日期:2002.3
The complex generated from BINOL, Zr(OtBu)4, and 4 Å MS in toluene–pivalonitrile is very effective for catalyticasymmetricallylation of aldehydes using allyltributyltin. The reactions of achiral aldehyde under these conditions are completed within 3 h using 10–20 mol% of the complex at −20°C. The ees of homoallylic alcohols can be enhanced up to 98% via the tandem asymmetric allylation–Oppenauer
由甲苯,新戊腈中的BINOL,Zr(O t Bu)4和4ÅMS生成的络合物对于使用烯丙基三丁基锡催化醛的催化不对称烯丙基化非常有效。在20°C下,使用10–20 mol%的配合物,可在3小时内完成这些条件下的非手性醛的反应。通过串联不对称烯丙基化-Oppenauer氧化可将均丙醇的ee提高至98%。对β-烷氧基醛的这些条件的范围和局限性进行了广泛的研究。
Gold-Catalyzed Tandem Cyclization of Dienol Silyl Ethers for the Preparation of Bicyclo[4.3.0]nonane Derivatives
Tandem bicycle: A gold‐catalyzed geminal carbo‐functionalization reaction of 3‐siloxy‐1,3‐dien‐8‐ynes proceeded smoothly to give bicyclo[4.3.0]nonanes stereoselectively through ring expansion of the bicyclic carbene complex intermediates. The product configuration was different from that of the thermal Diels–Alder adduct.
Asymmetric Ni-Catalyzed Conjugate Allylation of Activated Enones
作者:Joshua D. Sieber、James P. Morken
DOI:10.1021/ja710922h
日期:2008.4.1
The nickel-catalyzedenantioselective addition of allylboronic acid pinacol ester, allylB(pin), is described. This reaction is highly effective with dialkylidene ketones and favors the allylation of the benzylidene site in nonsymmetric substrates. The reaction appears to proceed by conversion of the dialkylidene ketone substrate to an unsaturated pi-allyl complex (I), followed by reductive elimination
Catalytic Conjugate Addition of Allyl Groups to Styryl-Activated Enones
作者:Joshua D. Sieber、Shubin Liu、James P. Morken
DOI:10.1021/ja067878w
日期:2007.2.1
Conjugateaddition of pinacolato(allyl)boron to benzylidenealkylidene ketones is remarkably facile when catalyzed by Ni(0) and Pd(0) complexes. Simpleenones are inert to the reaction conditions, suggesting a significant activating effect by the auxiliary benzylidene unit. A comparison of different catalysts and substrates is provided, as is a mechanistic rationale, and an example of asymmetric catalysis
Rhodium-catalyzedasymmetric conjugate alkynylation of α,β-unsaturatedketones giving β-alkynylketones took place in high yields with high enantioselectivity. The reaction was realized by use of (triisopropylsilyl)acetylene combined with (R)-DTBM-segphos as a chiral phosphine ligand, where the sterically bulky substituents on the silicon and phosphorus atoms suppress the alkyne dimerization.