Planar Chiral PHANOLs as Double Hydrogen Bonding Donor Organocatalysts: Synthesis and Catalysis
作者:D. Christopher Braddock、Iain D. MacGilp、Benjamin G. Perry
DOI:10.1002/adsc.200404065
日期:2004.8
4,12-Dihydroxy[2.2]paracyclophanediol (PHANOL; 1), and its para-substituted derivatives 2, 5 and 7, were found to catalyse Diels–Alder cycloadditions of α,β-unsaturated aldehydes or ketones with dienes and/or epoxide ringopening reactions with amines. The mode of catalysis by the PHANOLs is via double hydrogen bonding to the two sp2 lone pairs of a carbonyl group or the two lone pairs of the epoxide
发现4,12-二羟基[2.2]对环庚二醇(PHANOL; 1)及其对位取代的衍生物2、5和7可以催化α,β-不饱和醛或酮与二烯和/或环氧化物的狄尔斯-阿尔德环加成反应与胺的开环反应。PHANOLs的催化方式是通过氢键与羰基的两个sp 2孤对或环氧化物的两个孤对进行双氢键合。该PHANOLs的Diels-Alder反应的催化活性的顺序基本上与基于的吸电子基团的能力(一个或多个)的程度在预期的氢键供体强度相关的对位置。相反,由于对双氢键模式的空间干扰,邻位取代的PHANOL 10、11和14没有活性作为催化剂。为支持所提出的双氢键模式,讨论了各种PHANOL的1 H NMR和IR光谱数据。
Zinc Tetrafluoroborate Hydrate as a Mild Catalyst for Epoxide Ring Opening with Amines: Scope and Limitations of Metal Tetrafluoroborates and Applications in the Synthesis of Antihypertensive Drugs (<i>RS</i>)/(<i>R</i>)/(<i>S</i>)-Metoprolols
作者:Brahmam Pujala、Shivani Rana、Asit K. Chakraborti
DOI:10.1021/jo201473f
日期:2011.11.4
reaction at the benzylic carbon of the epoxide ring. A reversal of regioselectivity (91:1–69:31) in favor of the reaction at the terminal carbon of the epoxide ring was observed for reaction with morpholine. The regioselectivity was dependent on the electronic and steric factors of the epoxide and the pKa of the amine and independent of amine nucleophilicity. The role of the metal tetrafluoroborates is
已经研究了金属四氟硼酸盐与胺进行环氧化物开环反应的范围和局限性,并且发现Zn(BF 4)2 · x H 2 O是一种温和而有效的催化剂,在无溶剂条件下于200 ℃提供高收率。 rt具有出色的化学,区域和立体选择性。催化效率依次为Zn(BF 4)2 · x H 2 O≫ Cu(BF 4)2 · x H 2 O> Co(BF 4)2 ·6H 2 O≫ Fe(BF 4)2 ·6H2 O> LiBF 4与环己烯氧化物和Zn(BF 4)2 · x H 2 O≫ Co(BF 4)2 ·6H 2 O≫ Fe(BF 4)2 ·6H 2 O> Cu(BF 4)反应2 · x H 2 O,用于氧化二苯乙烯,但AgBF 4是无效的。对于苯乙烯氧化物与苯胺的反应,四氟硼酸金属具有相当的区域选择性(1:99–7:93),并且在环的苄基碳上具有优先反应。与吗啉反应时,观察到区域选择性的逆转(91:1–69:31),有
Manganese Complexes of Pyrrole‐ and Indolecarboxamide Ligands: Synthesis, Structure, Electrochemistry, and Applications in Oxidative and Lewis‐Acid‐Assisted Catalysis
作者:Sunil Yadav、Sushil Kumar、Rajeev Gupta
DOI:10.1002/ejic.201500773
日期:2015.11
N4 coordination sphere about the MnIII ion. The MnIII complexes of pyrrolecarboxamide ligands are square pyramidal with a fifth Cl atom, whereas analogous complexes of indolecarboxamide ligands are essentially square planar. Electrochemical studies reveal highly negative MnIII/II and moderately positive MnIV/III redox potentials. In situ generated Mn4+ species of the pyrrolecarboxamide ligands were
ZrCl4 as a new and efficient catalyst for the opening of epoxide rings by amines
作者:Asit K Chakraborti、Atul Kondaskar
DOI:10.1016/j.tetlet.2003.09.046
日期:2003.11
catalyses the nucleophilicopening of epoxide rings by amines leading to the efficient synthesis of β-amino alcohols. The reaction works well with aromatic and aliphatic amines in short times at room temperature in the absence of solvent. Exclusive trans stereoselectivity is observed for cyclic epoxides. Aromatic amines exhibit excellent regioselectivity for preferential nucleophilic attack at the
An efficient synthesis of 2-amino alcohols by silica gel catalysed opening of epoxide rings by amines
作者:Asit K. Chakraborti、Santosh Rudrawar、Atul Kondaskar
DOI:10.1039/b400588k
日期:——
catalyses the opening of epoxide rings by amines at rt under solvent-free conditions providing an easy method for the synthesis of 2-amino alcohols. Aromatic and aliphatic amines react with cyclohexene oxide with exclusive formation of the trans-2-aryl/alkylaminocyclohexanols in high yields. A complementary regioselectivity is exhibited by aromatic and aliphatic amines during the reaction with styrene