Chiral Covalent Organic Frameworks with High Chemical Stability for Heterogeneous Asymmetric Catalysis
作者:Xing Han、Qingchun Xia、Jinjing Huang、Yan Liu、Chunxia Tan、Yong Cui
DOI:10.1021/jacs.7b04008
日期:2017.6.28
Covalent organic frameworks (COFs) featuring chirality, stability, and function are of both fundamental and practical interest, but are yet challenging to achieve. Here we reported the metal-directed synthesis of two chiral COFs (CCOFs) by imine-condensations of enantiopure 1,2-diaminocyclohexane with C3-symmetric trisalicylaldehydes having one or zero 3-tert-butyl group. Powder X-ray diffraction and
具有手性、稳定性和功能的共价有机框架 (COF) 具有基本和实际意义,但实现起来仍具有挑战性。在这里,我们报道了通过对映纯 1,2-二氨基环己烷与具有一个或零个 3-叔丁基的 C3 对称三水杨醛的亚胺缩合,金属定向合成两种手性 COF(CCOF)。粉末 X 射线衍射和建模研究以及孔径分布分析表明,基于 Zn(salen) 的 CCOF 具有 AA 堆叠的二维六边形网格网络。与非烷基化类似物相比,在孔壁上掺入叔丁基的 COF 对酸性 (1 M HCl) 和碱性 (9 M NaOH) 条件的化学稳定性显着增强。CCOF 中的 Zn(salen) 模块允许通过合成后金属交换将多元金属安装到框架中。交换后的 CCOF 保持高结晶度和孔隙率,可作为高效且可回收的多相催化剂,用于醛的不对称氰化、Diels-Alder 反应、烯烃环氧化、环氧化物开环和相关的连续反应,ee 高达 97%。
A Cr(salen)-based metal–organic framework as a versatile catalyst for efficient asymmetric transformations
作者:Qingchun Xia、Yan Liu、Zijian Li、Wei Gong、Yong Cui
DOI:10.1039/c6cc06019f
日期:——
A porous Cr(salen)-MOF can serve as an efficient and effective heterogeneous catalyst for a series of important asymmetric transformations including Nazarov cyclization, aminolysis reaction, Diels-Alder and hetero Diels-Alder reactions, resulting...
Carbon-Substituted Co(III) Salens as Effective Catalysts for Enantioselective Diels-Alder Reactions
作者:Viresh H. Rawal、Jeff D. McGilvra
DOI:10.1055/s-2004-834799
日期:——
place of the bay region t-Bu or silyl substituents were synthesized and examined as catalysts for the enantioselectiveDiels-Alderreaction of 1-benzylaminocarbamate-1,3-butadiene and methacrolein. The results were consistent with a working model for rationalizing enantioselectivity in these cycloaddition reactions: an increase in the steric bulk of the internal substituents gives, in most instances
合成了七个新合成的 Co(III) salen 六氟锑酸盐配合物,其具有芳基或烷基-芳基取代基取代了湾区 t-Bu 或甲硅烷基取代基,并作为 1-苄氨基氨基甲酸酯-1,3 的对映选择性 Diels-Alder 反应的催化剂进行了研究-丁二烯和异丁烯醛。结果与在这些环加成反应中合理化对映选择性的工作模型一致:在大多数情况下,内部取代基空间体积的增加会导致加合物 ee 的可预测增加。最好的结果是用均苄基取代的 salen 获得的,与之前研究的 TMS-Co(III) salen 相比,它产生了 >97% ee 的环加合物,并且反应速率增加。这项研究的见解表明螺旋不对称,由增加内部取代基的空间尺寸引起的,单独不能解释产品的ee增加。本研究还表明,完全基于碳的取代基可以作为与三烷基硅烷一样有效的对映体区分元素,并且与硅烷不同,不易发生原脱甲硅烷化。
Broadly Effective Enantioselective Diels−Alder Reactions of 1-Amino-substituted-1,3-butadienes
作者:Yong Huang、Tetsuo Iwama、Viresh H. Rawal
DOI:10.1021/ol0255716
日期:2002.4.1
[GRAPHICS]A broad range of substituted 1-amino-1,3-butadienes undergo enantloselective Diels-Alder reactions with methacrolein in the presence of 5 mol % of Cr(III)-salen complex 1. The reactions are carried out conveniently, at room temperature, and they afford the cycloadducts in high yields and excellent ee's.
Design and Development of Highly Effective Lewis Acid Catalysts for Enantioselective Diels−Alder Reactions
作者:Yong Huang、Tetsuo Iwama、Viresh H. Rawal
DOI:10.1021/ja026088t
日期:2002.5.1
report describes the design and development of chiral Co(III)-salen catalysts for enantioselectiveDiels-Alderreactions. A crystal structure of a Co-salen catalyst with two equivalents of benzaldehyde provided insight on the factors that may be important for enantioselectivity. On the basis of this structural information, new catalysts were prepared in which the "bay region" tert-butyl groups were replaced