Kinetic resolution of 2-methoxycarbonylalk-3-enols through a stereoselective cyclofunctionalization promoted by an enantiomerically pure electrophilic selenium reagent
作者:Cristina Tomassini、Francesca Di Sarra、Bonifacio Monti、Luca Sancineto、Luana Bagnoli、Francesca Marini、Claudio Santi
DOI:10.3998/ark.5550190.p009.826
日期:——
In this manuscript the kinetic resolution of 2-methoxycarbonylalk-3-enols is reported through a stereoselective selenocyclization promoted by an electrophilic sulfur-containing selenium reagent. Reacting one equivalent of the selenenenylating agent with two equivalents of racemic starting material afforded a mixture of a stereoselectively enriched tetrahydrofuran and the corresponding enantiomerically enriched alkenols.[GRAPHICS].
Tandem Aldol-Cyclization Sequence for the Construction of Cyclic Ethers. The Formation of Substituted Tetrahydrofurans
作者:Paul Galatsis、Scott D. Millan、Patrik Nechala、George Ferguson
DOI:10.1021/jo00101a024
日期:1994.11
The application of a tandem deconjugative aldol-cyclization Sequence for the construction of substituted tetrahydrofurans was examined. The aldol condensation of alkenoates proceeded with alkylation at the alpha-position to generate homoallylic alcohol moieties. These compounds could be induced to cyclize under the influence of iodine via an endo mode. The stereoselectivity for the cyclization occurred in good to excellent fashion. X-ray crystal structure analysis of three of the tetrahydrofurans established unambiguously the product stereochemistry. This was: used to propose a transition structure for the cyclization which correctly predicts the observed product stereochemistry. By this method, virtually all the possible stereoisomers for the substituted tetrahydrofurans can be constructed by judicious choice of aldol product and/or olefin geometry.