The first primary aminocatalytic direct cross-aldol reaction of acetaldehyde is presented. Among the various vicinal diamines screened, the L-tert-leucine derivative 1c in conjunction with (H4SiW12O40)0.25 was identified as the optimal catalyst; good catalytic activity (up to 99 % yield in 4 h), and high enantioselectivities (up to 92 % ee) were achieved for a range of donors, including aromatic aldehydes
Chiral Primary−Tertiary Diamine Catalysts Derived From Natural Amino Acids for <i>syn</i>-Aldol Reactions of Hydroxy Ketones
作者:Jiuyuan Li、Sanzhong Luo、Jin-Pei Cheng
DOI:10.1021/jo802557p
日期:2009.2.20
A series of primary-tertiary diamine catalysts were designed and synthesized from primary natural amino acids. Application of these new chiral catalysts in direct aldol reactions of α-hydroxyketones showed very good catalytic activity (up to 97% yield) and high syn selectivity (up to syn/ anti = 30:1, 99% ee).
从伯天然氨基酸设计合成了一系列伯叔二胺催化剂。这些新的手性催化剂在α-羟基酮的直接醛醇缩合反应中的应用显示出非常好的催化活性(高达97%的收率)和高的合成选择性(高达syn / anti = 30:1,99%ee)。
Pd(II)-Catalyzed Enantioselective C(sp<sup>3</sup>)–H Arylation of Free Carboxylic Acids
chiral ligand based on an ethylenediamine backbone was developed to achieve Pd-catalyzed enantioselective C(sp3)-H arylation of cyclopropanecarboxylic and 2-aminoisobutyric acids without using exogenous directing groups. This new chiral catalyst affords new disconnection for preparing diverse chiral carboxylic acids from simple starting materials that are complementary to the various ring forming approaches
Physical Organic Study of StructureâActivityâEnantioselectivity Relationships in Asymmetric Bifunctional Thiourea Catalysis: Hints for the Design of New Organocatalysts
Correlations of pKa with catalytic activity and stereoselectivity were determined and linear free energy relationships (LFERs) were observed for both pKa−log (k) and pKa−log (R/S) correlations in meta‐ and/or para‐substituted aromatic thioureas (see figure). These results provided a basis for new catalyst development and several improved catalysts were identified in our initial attempts.
酸度效应:确定了p K a与催化活性和立体选择性之间的相关性,并在meta ‐中的p K a -log(k)和p K a -log(R / S)相关性中观察到线性自由能关系(LFER)。和/或对位取代的芳族硫脲(见图)。这些结果为新催化剂的开发提供了基础,并且在我们最初的尝试中发现了几种改进的催化剂。
Application of aziridinium ring opening for preparation of optically active diamine and triamine analogues: highly efficient synthesis and evaluation of DTPA-based MRI contrast enhancement agents
作者:Xiang Sun、Yunwei Chen、Ningjie Wu、Chi Soo Kang、Hyun A. Song、Shengnan Jin、Yao Fu、Henry Bryant、Joseph A. Frank、Hyun-Soon Chong
DOI:10.1039/c5ra11306g
日期:——
Ring opening of aziridinium ions with nitrogen nucleophiles was applied to the highly efficient synthesis of optically active vicinal diamines and diethylene triamine pentaacetic acid (DTPA) analogues as potential magnetic resonance imaging (MRI) contrast enhancement agents. The synthetic method features a column-free isolation of the regiospecific and stereospecific nucleophilic substitution products