A New Method for the Formation of Anti-apicophilic (O-cis) Spirophosphoranes – Kinetic Studies on the Stereomutation ofO-cis Arylspirophosphoranes to TheirO-trans Isomers
作者:Kazumasa Kajiyama、Miki Yoshimune、Satoshi Kojima、Kin-ya Akiba
DOI:10.1002/ejoc.200600031
日期:2006.6
P–H spirophosphorane 4 bearing two Martin ligands was converted to dianions (5a–n), bearing R groups, with excess organolithium reagents (RLi). Subsequent oxidation with I2 at ambient temperature gave anti-apicophilic (O-cis) spirophosphoranes 2a–n. All anti-apicophilic phosphoranes 2a–n isomerized irreversibly to the O-trans spirophosphoranes 3a–n, respectively. For 2,6-dialkylphenyl derivatives 2k–n
带有两个 Martin 配体的 P-H 螺正膦 4 被转化为带有 R 基团的二价阴离子 (5a-n),并带有过量的有机锂试剂 (RLi)。随后在环境温度下用 I2 氧化得到抗亲亲油性 (O-cis) 螺正膦 2a-n。所有反亲亲亲磷烷 2a-n 分别不可逆地异构化为 O-反式螺正膦 3a-n。对于 2,6-二烷基苯基衍生物 2k–n,对映异构体 2-RP 和 2-Sp 之间的假旋转势垒相当高,因此无法在 NMR 时间尺度上观察到相互转化。三异丙基苯基 (TIP) 衍生物 2n 到 3n 的假旋转活化参数与 nBu 衍生物 2b 到 3b 的激活参数几乎相同,即 ΔH‡ = 21.3 kcal mol–1,ΔS‡ = –9.4 eu。(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)