Synthesis of the A,B,C-Ring System of Hexacyclinic Acid
摘要:
[GRAPHICS]The synthesis of the A,B,C-ring system (2) of hexacyclinic acid (1) is achieved starting from a selective Diels-Alder reaction followed by vinyl cuprate addition. The diastereoselective reduction of the ketone carbonyl at C16 could be achieved with LiAlH4. An intramolecular Michael addition established the ring system stereoselectively, providing access to the selective generation of 9 out of the 14 stereocenters of hexacyclinic acid.
Activation of silanes by Grubbs’ carbene complex Cl2(PCy3)2RuCHPh: dehydrogenative condensation of alcohols and hydrosilylation of carbonyls
作者:Sarah V Maifeld、Reagan L Miller、Daesung Lee
DOI:10.1016/s0040-4039(02)01385-0
日期:2002.9
This manuscript describes two catalytic methods for silylether synthesis using Grubbs’ catalyst Cl2(PCy3)2RuCHPh. Silylethers are obtained from the reaction of a variety of silanes with alcohols by dehydrogenative condensation and by the hydrosilylation of carbonyl compounds. Both reactions occur under neat conditions.
Synthesis of (−)‐Hebelophyllene E: An Entry to Geminal Dimethyl‐Cyclobutanes by [2+2] Cycloaddition of Alkenes and Allenoates
作者:Johannes M. Wahl、Michael L. Conner、M. Kevin Brown
DOI:10.1002/anie.201801110
日期:2018.4.16
The first synthesis of hebelophyllene E is presented, along with assignment of its previously unknown relative configuration through synthesis of epi‐ent‐hebelophyllene E. Development of a catalytic enantioselective [2+2] cycloaddition of alkenes and allenoates provides access to the required chiral geminal dimethylcyclobutanes. Key to its success is the identification of a novel oxazaborolidine catalyst
A Novel Method for the Preparation of Acid-Sensitive Epoxides from Olefins with the Combined Use of Molecular Oxygen and Aldoacetal Catalyzed by a Cobalt(II) Complex
An efficient synthesis of acid-sensitive epoxides, such as chromene oxide or epoxide of γ,δ-unsaturated alcohol, was successfully achieved by the oxygenation of corresponding olefins with the combined use of an atmospheric pressure of molecular oxygen and aldoacetal catalyzed by a cobalt(II) complex coordinated with the 1,3-diketone ligand. The reactions proceeded under mild and neutral conditions
cross-metathesis is the key step. This reaction has proved to be highly regioselective, allowing the combination of α- or β-ionone derivatives having a 1,1-disustituted olefin with trisubstituted alkenes. The stereochemistry of the newly formedolefins has been established by spectroscopic means.
In the presence of bis(3-methyl-2,4-pentanedionato)cobalt(II) complex catalyst, various trisubstituted olefins are smoothly monooxygenated into the corresponding epoxides in high yields under neutral conditions by the combined use of molecular oxygen and propionaldehyde diethyl acetal.