Diastereofacial selectivity in reactions of substituted cyclohexyl radicals. An experimental and theoretical study
作者:W. Damm、B. Giese、J. Hartung、T. Hasskerl、K. N. Houk、O. Hueter、H. Zipse
DOI:10.1021/ja00037a007
日期:1992.5
diastereofacial selectivity in reactions of a series of alkyl-substituted cyclohexylradicals has been investigated. In additions of cyclohexylradicals to alkenes, it has been found that only substituents bound at the olefinic center being attacked by the radical influence the equatorial-axial selectivity. Substituents bound to the radical center or axial substituents p to the radical center lead to increased
We have developed a practical stereoretentive iodine/lithium‐exchange process that allows the stereodefined preparation of cis‐ and trans‐cycloalkyllithium compounds from their corresponding stereodefined iodides. Quenching with electrophiles offers stereospecific access to both cis‐ (up to 96 % cis) and trans‐cycloalkyl derivatives (up to 99 % trans). A detailed study of the thermodynamic stabilities
function with an acidic NH group were prepared using the direct insertion of zinc dust into the corresponding alkyl iodides in THF or THF:DMSO mixtures. Most of the starting iodides were obtained from natural α-amino acids and the resulting zinc species afforded after transmentalation with CuCN·2LiCI and reaction with a selection of relatively reactive electrophiles a variety of polyfunctional 1,2-amino
The quasi-homo-anomeric interaction in substituted tetrahydropyranyl radicals: Diastereoselectivity
作者:Athelstan L.J. Beckwith、Peter J. Duggan
DOI:10.1016/s0040-4020(98)00373-1
日期:1998.6
of simple cyclohexyl and tetrahydropyranyl radicals (3 – 7) with Bu3SnD and with allyltributyltin, has been determined in order to gauge the influence of the classical anomeric effect and the quasi-homo-anomeric effect on stereoselectivity. In these unencumbered radicals, both anomeric effects caused a strong preference for trans deuterated products, but no significant stereoselectivity was observed