Asymmetric inter- and intramolecular cyclopropanation of alkenes catalyzed by chiral ruthenium porphyrins. Synthesis and crystal structure of a chiral metalloporphyrin carbene complex
Asymmetric inter- and intramolecular cyclopropanation of alkenes catalyzed by chiral ruthenium porphyrins. Synthesis and crystal structure of a chiral metalloporphyrin carbene complex
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DOI：
10.1021/ja001416f
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发表时间：
2001-05-09
影响因子：
15
通讯作者：
Zhou, ZY
中科院分区：
文献类型：
--
作者：
Che, CM;Huang, JS;Zhou, ZY
本文报道了钌卟啉[Ru（P ~*）（CO）（EtOH）]（1，H_2P ~* = 5，10，15，20-四-{[1 S，4 R，5 R，8 S]-1，2，3，4，5，6，7，8-八氢-1，4：5，8-二甲蒽-9-基}卟啉）催化的末端烯烃与重氮乙酸酯的不对称分子内环丙烷化反应，以及催化剂1在烯丙基或高烯丙基重氮乙酸酯的不对称分子内环丙烷化反应中的应用。苯乙烯及其衍生物与重氮乙酸乙酯的分子间环丙烷化反应得到了相应的环丙基酯，其ee值高达98%，反式/顺式比率高达36，催化剂转化率高达1.1 × 10 - 4。考察了温度、重氮乙酸酯、溶剂和取代基对分子间环丙烷化反应的影响，结果表明：（i）对映选择性和反式选择性均随温度的降低而增加;（ii）空间位阻的重氮乙酸酯N_2CHCO_2R，如R = Bu-t，以及给体溶剂，如乙醚和四氢呋喃，有利于反式选择性的提高，（iii）苯乙烯上的给电子帕拉取代基促进了环丙烷化反应，对位取代苯乙烯p-X-C6 H4 CH = CH 2的log（k（X）/k（H））vs sigma（+）曲线（X = MeO、Me、Cl、CF 3），表现出良好的线性，具有-0.44 +/-0.09的小负rho（+）值。在分子内环丙烷化反应中，配合物1促进了一系列烯丙基重氮乙酸酯分解生成环丙基内酯，其ee值高达85%，是第一个高效的不对称分子内环丙烷化反应金属卟啉催化剂。分子间和分子内的环丙烷化反应都是通过反应性手性钌卡宾中间体进行的。通过对手性卡宾配合物[Ru（P*）（CPh 2）]（2）和[Ru（P*）（C（Ph）-CO2 CH 2CH = CH 2）]（3）的X-射线晶体结构的分析，对上述反应的对映选择性进行了合理化。
Extensive investigations of asymmetric intermolecular cyclopropanation of terminal alkenes with diazoacetates catalyzed by ruthenium porphyrin [Ru(P*)(CO)(EtOH)] (1, H2P* = 5,10,15,20-tetrakis-{[1S,4R,5R,8S)-1,2,3,4,5,6,7,8-octahydro-1,4:5,8-dimethanoanthracene-9-yl}porphyrin) and the application of catalyst 1 to asymmetric intramolecular cyclopropanation of allylic or homoallylic diazoacetates are described. The intermolecular cyclopropanation of styrene and its derivatives with ethyl diazoacetate afforded the corresponding cyclopropyl esters in up to 98% ee with high trans/cis ratios of up to 36 and extremely high catalyst turnovers of up to 1.1 x 10(4). Examination of the effects of temperature, diazoacetate, solvent, and substituent in the intermolecular cyclopropanation reveals that (i) both enantioselectivity and trans selectivity increase with decreasing temperature, (ii) sterically encumbered diazoacetates N2CHCO2R, such as R = Bu-t, and donor solvents, such as diethyl ether and tetrahydrofuran, are beneficial to the trans selectivity, and (iii) electron-donating para substituents on styrene accelerate the cyclopropanations, with the log(k(X)/k(H)) vs sigma (+) plot for para-substituted styrenes p-X-C6H4CH=CH2 (X = MeO, Me, Cl, CF3) exhibiting good linearity with a small negative rho (+) value of -0.44 +/- 0.09. In the case of intramolecular cyclopropanation, complex 1 promoted the decomposition of a series of allylic diazoacetates to form the cyclopropyl lactones in up to 85% ee, contributing the first efficient metalloporphyrin catalyst for an asymmetric intramolecular cyclopropanation. Both the inter- and intramolecular cyclopropanations were proposed to proceed via a reactive chiral ruthenium carbene intermediate. The enantioselectivities in these processes were rationalized on the basis of the X-ray crystal structures of closely related stable chiral carbene complexes [Ru(P*)(CPh2)] (2) and [Ru(P*)(C(Ph)-CO2CH2CH=CH2)] (3) obtained from reactions of complex 1 with N2CPh2 and N2C(Ph)CO2CH2CH=CH2, respectively.