Facile separation catalyst system: direct diastereoselective synthesis of (E)-α,β-unsaturated ketones catalyzed by an air-stable Lewis acidic/basic bifunctional organobismuth complex in ionic liquids
The catalyst system that comprises an air-stable bifunctional Lewis acidic/basic organobismuth complex and [Bmim]BF4 is highly efficient in the cross-condensation of aldehydes with ketones. Through switching the reaction from homogeneous to heterogeneous, the system shows facile separation ability and facile reusability.
Synthesis of (+)-Madindoline A and (+)-Madindoline B
作者:Lifeng Wan、Marcus A. Tius
DOI:10.1021/ol062919e
日期:2007.2.1
The allene ether version of the Nazarovcyclization was used to construct the cyclopentane dione portion of madindolines A and B. The racemic cyclopentane dione from the Nazarovcyclization was converted to an enol ether that was combined with the chiral, nonracemic hydroxyfuroindoline in a Mannich reaction. Deprotection and oxidation led to (+)-madindoline A and (+)-madindoline B. [reaction: see text]
An efficient total synthesis of (±)-xanthocidin, a complex and unstable cyclopentanoid antibiotic, is described. The success of the key cyclopentannelation step suggests much greater versatility for the general version of this reaction.
Two-Step Formal [3+2] Cycloaddition of Enones/Enals and Allenyl MOM Ether: Gold-Catalyzed Highly Diastereoselective Synthesis of Cyclopentanone Enol Ether Containing an All-Carbon Quaternary Center
作者:Xiaogen Huang、Liming Zhang
DOI:10.1021/ja0717717
日期:2007.5.1
A two-step, highlydiastereoselectiveformal [3+2] cycloaddition between allenyl MOM ether and an enal/enone is developed. Au activation of allenyl ethers is proposed to yield all-carbon 1,3-dipoles, which can undergo concerted intramolecular 1,3-dipolar cycloadditions. Synthetically useful cyclopentanone enol ethers containing an all-carbon quaternary center can be readily prepared with excellent
开发了烯基 MOM 醚和烯醛/烯酮之间的两步、高度非对映选择性的正式 [3+2] 环加成反应。建议对烯基醚进行 Au 活化以产生全碳 1,3-偶极子,其可以进行协同的分子内 1,3-偶极环加成。合成有用的环戊酮烯醇醚含有全碳季中心,可以很容易地制备,并具有优异的非对映控制。
Terpestacin Core Structure. Control of Stereochemistry
作者:Gideon O. Berger、Marcus A. Tius
DOI:10.1021/ol052015d
日期:2005.10.1
[reaction: see text] The alpha-hydroxycyclopentenone corestructure of terpestacin has been prepared in a model system through an allene ether Nazarov cyclization of an alkylidene-gamma-butyrolactone followed by regio- and stereoselective alkylation reactions. The stereochemistry at C15 (terpestacin numbering) has been used to control stereochemistry at C1 and at C23. The use of E-alkylidene-gamma-butyrolactones