CHIRAL RUTHENIUM(II)-BIS(2-OXAZOLIN-2-YL) PYRIDINE COMPLEXES - ASYMMETRIC CATALYTIC CYCLOPROPANATION OF OLEFINS AND DIAZOACETATES
CHIRAL RUTHENIUM(II)-BIS(2-OXAZOLIN-2-YL) PYRIDINE COMPLEXES - ASYMMETRIC CATALYTIC CYCLOPROPANATION OF OLEFINS AND DIAZOACETATES
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DOI：
10.1246/bcsj.68.1247
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发表时间：
1995-01-01
影响因子：
4
通讯作者：
ITOH, K
中科院分区：
文献类型：
--
作者：
NISHIYAMA, H;ITOH, Y;ITOH, K
由光学活性双(2-恶唑啉-2-基)吡啶(PYBOX-IP)(2)和[RuCl2(对伞花烃)](2)(1)原位合成的手性Ru(II)-双(2-恶唑啉-2-基)吡啶催化剂对苯乙烯和几种重氮乙酸酯的不对称环丙烷化反应(ACP)表现出高效的催化活性，得到了相应的反式和顺式-2-苯基环丙烷-1-羧酸酯(3和4)，产率很高(66-87%)。在乙烯气氛中，1和2的混合物生成了反式RuCl2(Pybox-IP)(乙烯)络合物(5)，该络合物也被证明是ACP的有力催化剂。反式和顺式环丙烷的立体选择性从90：10到98：2，对映体选择性达到97%。含5的催化体系可用于多种烯烃和内烯烃的催化反应。根据与氚代苯乙烯的立体专一性，推测了ACP与Ru-PYBOX催化剂的协同作用机理。还考察了取代异丙基的吡唑啉环上的其他取代基，如乙基、S丁基、苯基和苯基，发现它们表现出与环丙烷类似的高反式立体选择性和高对映体选择性。非手性Ru-Py-box-二氢催化剂对d-和L-重氮乙酸薄荷酯的不对称诱导反应显示出39%的Ees，并保持了97：3的高反式和顺式立体选择性。
A chiral ruthenium(II)-bis(2-oxazolin-2-yl)pyridine catalyst prepared in situ from optically active bis(2-oxazolin-2-yl)pyridine (Pybox-ip) (2) and [RuCl2(p-cymene)](2) (1) exhibited efficient activity for the asymmetric cyclopropanation (ACP) of styrene and several diazoacetates to give the corresponding trans- and cis-2-phenylcyclopropane-1-carboxylates (3 and 4) in good yields (66-87%). A mixture of 1 and 2 in an atmosphere of ethylene produced the trans-RuCl2 (Pybox-ip)(ethylene) complex (5), which also proved to be a powerful catalyst for ACP. The stereoselectivity of the trans- and cis-cyclopropanes were from 90:10 up to 98:2, and their enantioselectivities reached 97%. A catalytic system with 5 could be used for several olefins and internal olefins. A concerted mechanism of ACP with the Ru-Pybox catalyst was postulated on the basis of the stereospecificity with deuterated styrene. Other substituents, such as ethyl, s-butyl, benzyl, and phenyl on the oxazoline rings of Pybox in place of the isopropyl group were also examined, and were found to exhibit a similar high trans-stereoselection and a high enantioselectivity of the cyclopropane products; ex. with Ru-Pybox-ethyl 91:9 of 3:4 and 82% ee for 3. The non-chiral Ru-Pybox-dihydro catalyst exhibited asymmetric induction with 39% ees of 3 with d- and l-menthyl diazoacetates, and kept a high trans- and cis-stereoselection of 97:3.