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