Ruffling-Induced Chirality: Synthesis, Metalation, and Optical Resolution of Highly Nonplanar, Cyclic, Benzimidazole-Based Ligands
摘要:
Expedient five-step syntheses of a cyclic bis(benzimidazole)-based amide 5 and two sterically more hindered analogues 23-24 have been developed. These amides are chiral due to the inherent ruffling of the macrocyclic plane. Racemization of the optical antipodes of these compounds has been studied using dynamic chiral stationary phase HIPLC. These studies reveal that, while the parent amide 5 racemizes rapidly, for the sterically more hindered amides 23-24, the rate of racemization is significantly reduced. Bis(benzimidazole)-based amides 5 and 23-24 form stable Ni(II) complexes 25-27, respectively. Like their parent ligands, complexes 25-27 are chiral due to their highly ruffled geometry. Studies of these complexes by chiral stationary phase HPLC reveal that metalation leads to a much lower rate of racemization. Incorporation of a strap can slow racemization even further. A series of strapped cyclic amides 54-57, along with their corresponding dinners 58-61, have been prepared. The rate of racernization for amides 54-57 is strongly dependent on the length of the strap. X-ray single-crystal structure analysis of the Ni(II) complex of strapped amide 54 reveals that the bis(benzimidazole) core retains its highly ruffled shape, with the two phenyl rings of the macrocycle located anti to the strap. Chiral separation of strapped ligands 54-57 and their corresponding Ni(II) complexes is shown to be facile by chiral stationary phase HPLC.
Ruffling-Induced Chirality: Synthesis, Metalation, and Optical Resolution of Highly Nonplanar, Cyclic, Benzimidazole-Based Ligands
摘要:
Expedient five-step syntheses of a cyclic bis(benzimidazole)-based amide 5 and two sterically more hindered analogues 23-24 have been developed. These amides are chiral due to the inherent ruffling of the macrocyclic plane. Racemization of the optical antipodes of these compounds has been studied using dynamic chiral stationary phase HIPLC. These studies reveal that, while the parent amide 5 racemizes rapidly, for the sterically more hindered amides 23-24, the rate of racemization is significantly reduced. Bis(benzimidazole)-based amides 5 and 23-24 form stable Ni(II) complexes 25-27, respectively. Like their parent ligands, complexes 25-27 are chiral due to their highly ruffled geometry. Studies of these complexes by chiral stationary phase HPLC reveal that metalation leads to a much lower rate of racemization. Incorporation of a strap can slow racemization even further. A series of strapped cyclic amides 54-57, along with their corresponding dinners 58-61, have been prepared. The rate of racernization for amides 54-57 is strongly dependent on the length of the strap. X-ray single-crystal structure analysis of the Ni(II) complex of strapped amide 54 reveals that the bis(benzimidazole) core retains its highly ruffled shape, with the two phenyl rings of the macrocycle located anti to the strap. Chiral separation of strapped ligands 54-57 and their corresponding Ni(II) complexes is shown to be facile by chiral stationary phase HPLC.
This report describes the synthesis of a seventeen-membered macrocyclic ring containingligand (L1) by the reaction of 1,8-bis(2-(chloromethyl)phenoxy)octane with selenium powder. The trans-palladium dichloride complex (C1) of the macrocyclic selenium ligand was synthesized from its reaction with the Pd(CH3CN)2Cl2 precursor. The formation of the ligand and complex was authenticated with the help of
本报告描述了通过 1,8-双(2-(氯甲基)苯氧基)辛烷与硒粉的反应合成含有配体 ( L1 )的十七元大环。大环硒配体的反式-二氯化钯络合物( C1 )是通过其与Pd(CH 3 CN) 2 Cl 2前体的反应合成的。借助1 H 和13 C 1等各种分析技术验证了配体和复合物的形成H} NMR、HRMS、FTIR、紫外-可见光谱和元素分析。借助单晶 X 射线衍射验证了配体的结构及其与钯前体的配位模式。该复合物在钯中心周围具有扭曲的方形平面几何形状。新的配体和复合物对空气和湿气不敏感,并且在室温下稳定三个月以上。变温核磁共振数据和计算研究表明钯络合物 ( C1 ) 中的硒反转具有~22.6 kcal mol -1的反转势垒。钯配合物C1用作含二羟基化合物的长烷基链脱羟甲基化的催化剂。通常,两种单独的催化剂用于脱羟甲基化(一种用于醇的氧化,另一种用于醛的脱羰基)。在这里,单一催化剂显示出脱羟甲基化的双重作用,在仅
Dehydrogenative Intramolecular Macrolactonization of Dihydroxy Compounds Using Ru-MACHO Catalyst
[EN] STRAPPED AND MODIFIED BIS (BENZIMIDAZOLE) DIAMIDES FOR ASYMMETRIC CATALYSTS AND OTHER APPLICATIONS<br/>[FR] BIS(BENZIMIDAZOLE)DIAMIDES PONTES ET MODIFIES POUR CATALYSEURS ASYMETRIQUES ET AUTRES APPLICATIONS
申请人:UNIV OHIO STATE RES FOUND
公开号:WO2003057667A2
公开(公告)日:2003-07-17
New compounds that are similar in function to tetrapyrrole ligands are provided. The basic framework consists of three classes of homochiral cyclic bis(benzimidazole) ligands: (1) bis(benzamidazoles) having Schiff base linkages; (2) bis(benzimidazoles) with diamime linkages; and (3) bis(benzimidazoles) with diamide linkages. Complexes of these ligands are also provided. The bis(benzimidazole) ligands further comprise a strap that lessens or precludes racemization of ligands or their complexes. These homochiral ligands are useful as catalysts for many types of reactions, including asymmetric epoxidation, epoxide ring opening. Diels-Alder, hereto Diels-Alder, asymmetric oxidation of benzylic hydrocarbons, oxidation of sulfides, hydroxylation, aziridination, cyclopropanation, kinetic resolution of allenes and other cumulenes, and the addition of HCN to imines. Also provided are polymer supports comprising the homochiral bis(benzimidazole) ligands and complexes.
Ruffling-Induced Chirality: Synthesis, Metalation, and Optical Resolution of Highly Nonplanar, Cyclic, Benzimidazole-Based Ligands
作者:Tomasz Fekner、Judith Gallucci、Michael K. Chan
DOI:10.1021/ja030196d
日期:2004.1.1
Expedient five-step syntheses of a cyclic bis(benzimidazole)-based amide 5 and two sterically more hindered analogues 23-24 have been developed. These amides are chiral due to the inherent ruffling of the macrocyclic plane. Racemization of the optical antipodes of these compounds has been studied using dynamic chiral stationary phase HIPLC. These studies reveal that, while the parent amide 5 racemizes rapidly, for the sterically more hindered amides 23-24, the rate of racemization is significantly reduced. Bis(benzimidazole)-based amides 5 and 23-24 form stable Ni(II) complexes 25-27, respectively. Like their parent ligands, complexes 25-27 are chiral due to their highly ruffled geometry. Studies of these complexes by chiral stationary phase HPLC reveal that metalation leads to a much lower rate of racemization. Incorporation of a strap can slow racemization even further. A series of strapped cyclic amides 54-57, along with their corresponding dinners 58-61, have been prepared. The rate of racernization for amides 54-57 is strongly dependent on the length of the strap. X-ray single-crystal structure analysis of the Ni(II) complex of strapped amide 54 reveals that the bis(benzimidazole) core retains its highly ruffled shape, with the two phenyl rings of the macrocycle located anti to the strap. Chiral separation of strapped ligands 54-57 and their corresponding Ni(II) complexes is shown to be facile by chiral stationary phase HPLC.