New chiral spiro[2.5]octanones as products of methylenation of (3R, 6R)-2-arylidene-6-isopropyl-3-methylcyclohexanones with dimethylsulfoxonium methylide. Synthesis, stereochemistry, and behavior in liquid-crystalline systems
作者:I. M. Gella、N. S. Pivnenko、L. A. Kutulya、T. G. Drushlyak、A. Yu. Kulikov、N. B. Novikova
DOI:10.1007/s11172-006-0130-5
日期:2005.10
methylenation of the compound with X = Ph as an example, a mixture of by-products resulting from oxidative hydroxylation at the α-position relative to the carbonyl group was isolated. The resulting chiral spiro[2.5]octanones induce a helical supramolecular ordering in the nematic mesophase of 4-pentyl-4′-cyanobiphenyl and exhibit a twisting power only somewhat (by 20–30%) lower than the starting enones.
(3R,6R)-2-(4-X-亚苄基)-6-异丙基-3-甲基环己酮 (X = F, Cl, Ph) 与二甲基亚砜发生立体选择性的甲基化反应,得到 1(S)-(4-X) -苯基)-5(R)-异丙基-8(R)-甲基-3(R)-螺[2.5]辛酮,其立体化学由1H NMR光谱确定。环己酮片段中手性中心的构型及其产物中的优选构象(甲基是轴向的,异丙基是赤道的)相对于起始烯酮没有改变。在新形成的三元环上建立了羰基和芳基的相互反式排列;芳基还占据环己酮片段的轴向甲基的转位。以 X = Ph 的化合物的亚甲基化为例,分离出在相对于羰基的α-位氧化羟基化产生的副产物混合物。由此产生的手性螺[2.5]辛酮在 4-戊基-4'-氰基联苯的向列中间相中诱导螺旋超分子排序,并且其扭曲能力仅比起始烯酮低一些(20-30%)。