First characterization of a 10-P-5 spirophosphorane with an apical carbon-equatorial oxygen ring. Kinetic studies on pseudorotation of stereoisomers
First characterization of a 10-P-5 spirophosphorane with an apical carbon-equatorial oxygen ring. Kinetic studies on pseudorotation of stereoisomers
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DOI：
10.1021/ja9621408
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发表时间：
1996-12-18
影响因子：
15
通讯作者：
Akiba, K
中科院分区：
文献类型：
--
作者：
Kojima, S;Kajiyama, K;Akiba, K
10-P-51正膦在基态通常呈现三角双锥结构，其中有两个独特的位置，顶端和赤道位置。2众所周知，根据元素的亲顶性，带有氧和碳取代基的正膦优先在顶端位置具有氧原子作为最稳定的立体异构体。2，3最近，据报道，一种特别设计的四氧正膦，其中碳取代基由于空间位阻而占据顶端位置，可以作为唯一可检测的异构体分离出来。4在这里，我们报告的第一个分离和表征的螺正膦具有顶端的碳-赤道氧五元环和其更稳定的顶端的氧-赤道碳异构体，并讨论这些立体异构体的相对热稳定性的动力学研究的基础上。当PH（赤道）螺正膦1 [~（31）P NMR（CDCl ~ 3）δ-45.8（1 JPH）729 Hz）] 5，6用大于2当量的正丁基锂在乙醚中处理，然后用稀盐酸仔细处理，我们得到单环PH（顶端）正膦27 [90%; mp 119 ℃; 19 F NMR（CDCl 3）δ-72.9（br s，3F），-76.3（q，4JFF）9.2Hz，3F），-76.8（q，4JFF）8.2Hz，3F），-77.0（qq，4JFF）9.2Hz，9 JFF）4.9Hz，3F）]和带有丁基的螺正膦3 [9%; mp 109 ℃; 31 P NMR（CDCl 3）δ
10-P-51 phosphoranes usually assume trigonal bipyramidal structures in the ground state, in which there are two distinctive sites, the apical and the equatorial positions. 2 It is well-known that a phosphorane bearing oxygen and carbon substituents preferentially has oxygen atoms in the apical positions as the most stable stereoisomer according to the apicophilicity of the elements. 2, 3 Quite recently, it was reported that a specially designed tetraoxyphosphorane in which a carbon substituent occupies the apical position due to steric hindrance could be isolated as the only detectable isomer. 4 Here, we report on the first isolation and characterization of a spirophosphorane having an apical carbon-equatorial oxygen five-membered ring and its thermodynamically more stable apical oxygen-equatorial carbon isomer and discuss the relative thermal stability of these stereoisomers on the basis of kinetic studies. When PH (equatorial) spirophosphorane 1 [31P NMR (CDCl3) δ-45.8 (1JPH) 729 Hz)] 5, 6 was treated with more than 2 equiv of n-BuLi in ether and carefully treated with dilute hydrochloric acid, we obtained monocyclic PH (apical) phosphorane 27 [90%; mp 119 C; 31P NMR (CDCl3) δ-34.4 (1JPH) 273 Hz); 19F NMR (CDCl3) δ-72.9 (br s, 3F),-76.3 (q, 4JFF) 9.2 Hz, 3F),-76.8 (q, 4JFF) 8.2 Hz, 3F),-77.0 (qq, 4JFF) 9.2 Hz, 9JFF) 4.9 Hz, 3F)] and spirophosphorane 3 bearing a butyl group [9%; mp 109 C; 31P NMR (CDCl3) δ