Ynolates were found to react with alpha-alkoxy-, alpha-siloxy-, and alpha-aryloxyketones at room temperature to afford tetrasubstituted olefins with high Z selectivity. Since the geometrical selectivity was determined in the ring opening of the beta-lactone enolate intermediates, the torquoselectivity was controlled by the ethereal oxygen atoms. From experimental and theoretical studies, the high Z
New Methylene Homologation Method for Cyclic Ketones
作者:Huaqing Liu、Chunrui Sun、Nam-Kyu Lee、Roger F. Henry、Daesung Lee
DOI:10.1002/chem.201201346
日期:2012.9.17
Teaching new tricks to an old dog: By intercepting adducts between ketones and lithium trimethylsilyldiazomethane, a new Tiffeneau–Demjanov type methylenehomologation could be realized in a single‐step operation. Among proton sources and Lewis acids, silica gel was found to be the most effective reagent for the protonation of intermediates and their subsequent ring expansion (see scheme).
A Ring Fragmentation Approach to Medium-Sized Cyclic 2-Alkynones
作者:Nikolay P. Tsvetkov、Ali Bayir、Samuel Schneider、Matthias Brewer
DOI:10.1021/ol2030422
日期:2012.1.6
Bicyclic gamma-silyloxy-beta-hydroxy-alpha-diazoketones, in which the C beta-C gamma bond is the ring fusion bond, productively fragment when treated with tin(IV) chloride to provide medium-sized cyclic 2-alkynones. This method provides good to excellent yields of 10-, 11-, and 12-membered alkynone products.