Synthesis and structure of large difluoromethylene containing alicycles by ring closing metathesis (RCM)
作者:Maciej Skibiński、César A. Urbina-Blanco、Alexandra M. Z. Slawin、Steven P. Nolan、David O'Hagan
DOI:10.1039/c3ob42062k
日期:——
Cyclotetra- and cyclohexa-decane ring systems were prepared with CF2 groups spaced 1,4- and 1,6- for tetradecanes together with 1,5- and 1,6- for hexadecanes. These alicyclic systems were assembled by ring closing metathesis reactions of long terminal diolefins. Ring cyclisation by RCM was promoted by the introduction of the dithiane motif, using a sulfur compatible metathesis catalyst. This gave rise to macrocyclic E-cycloalkanes, which were hydrogenated also using a sulfur compatible catalyst. Finally the dithianes emerged as appropriate precursor motifs for the introduction of difluoromethylene groups. X-Ray structures revealed that the resultant rings have the CF2 groups located only at corner positions and that these groups dictated the overall macrocyclic ring conformations.
环十四烷和环十六烷的环系统由间隔为1.4和1.6的CF2基团组成,而环十六烷的环系统由间隔为1.5和1.6的CF2基团组成。这些脂环系统是通过长端二烯烃的环闭合复分解反应组装而成的。通过引入二噻烷基团,使用硫兼容复分解催化剂,促进了RCM的环化反应。这产生了大环E-环烷,也使用硫兼容催化剂对其进行氢化。最后,二噻烷作为引入二氟亚甲基基团的合适前体基团出现。X射线结构显示,所得环的CF2基团仅位于角位,这些基团决定了整体大环的环构象。