Optically Pure (<i>S</i>)-6,7-Dimethoxy-1,2,3,4-Tetrahydro-3-Isoquinolinecarboxylic Acid and Asymmetric Hydrogenation Studies Related to Its Preparation
作者:N. J. O'Reilly、W. S. Derwin、H. C. Lin
DOI:10.1055/s-1990-26936
日期:——
(S)-6,7-Dimethoxy-1,2,3,4-tetrahydro-3-isoquinolinecarboxylic acid has been prepared in optically pure form as its hydrochloride. Pictet-Spengler ring closure of the optically pure (S)-2-amino-3-(3,4-dimethoxyphenyl)propanoic acid hydrochloride salt (L-3,4-dimethoxyphenylalanine hydrochloride) proceeded without significant racemization. A simple and safe, asymmetric hydrogenation catalyst system has been developed which allows the rapid screening of various chiral phosphine ligands via an in situ ionic complex. A protocol was demonstrated which uses a statistical approach to consider the effects of changes in solvent, nitrogen substituent, oxygen substituent, and ligand in the asymmetric hydrogenation of alkyl or aryl (Z)-2-acylamino-3-(3,4-dimethoxyphenyl)-2-propenoate derivatives. This method was used to successfully determine the optimal substrate and conditions for the preparation of enantiomerically pure (S)-2-amino-3-(3, 4-dimethoxyphenyl)propanoic acid hydrochloride salt.
Easy access to drug building-blocks through benzylic C–H functionalization of phenolic ethers by photoredox catalysis
作者:Tobias Brandhofer、Martin Stinglhamer、Volker Derdau、María Méndez、Christoph Pöverlein、Olga García Mancheño
DOI:10.1039/d1cc01756j
日期:——
A visible light-mediated photocatalyzed C–C-bond forming method for the benzylic C–H functionalization of phenolether containing synthetic building blocks based on a radical-cation/deprotonation strategy is reported. This method allows the mild, selective generation of benzyl radicals in phenolic complex molecules and drug-like compounds, providing new entries in synthetic and medicinal chemistry.
报道了一种基于自由基阳离子/去质子化策略的可见光介导的光催化 C - C 键形成方法,用于含合成结构单元的苯酚醚的苄基 C-H 官能化。该方法允许在酚类复合物分子和类药物化合物中温和、选择性地生成苄基,为合成和药物化学提供了新的入口。
Asymmetric hydrogenation - influence of the structure of carbohydrate derived catalysts on the relative enantioselectivity QH/Me regarding acid and ester substrates and its inversion - selectivity increase in water by amphiphiles
作者:Rüdiger Selke、Manuela Ohff、Andreas Riepe
DOI:10.1016/s0040-4020(96)00953-2
日期:1996.11
resulting in an unusual low relative enantioselectivityQ=qH/qMe of 0.3 for the precatalysts 4e and 4f. Deprotected, 4,6-OH-group bearing catalysts 1-4g,h generally show smaller differences of %ee in methanol or benzene, however, not in water. Under addition of amphiphiles a in comparison with blanks b the relative enantioselectivity Q=qa/qb clearly increases for both groups of catalysts- in most cases
4,6 - O-苄叉基保护的2,3-双(O-二苯基膦基)-δ-吡喃葡萄糖苷铑(I)螯合物预催化剂1-4e ,f显示了对(Z)-2- N-酰氨基丙烯酸甲酯的加氢作用6 -8随轴向取向的六吡喃糖苷取代基数量的增加,对映选择性逐步降低。对于类似的底物酸6h-8h的降低甚至更强,导致预催化剂4e和4f的相对低的相对对映选择性Q = q H / q Me为0.3。脱保护的含4,6-OH基的催化剂1-4g,h通常在甲醇或苯中显示出较小的%ee差异,而在水中则显示出较小的%ee差异。与空白b相比,在添加两亲性a的情况下,两组催化剂的相对对映选择性Q = q a / q b明显增加-在大多数情况下,Q值在3到8之间-与催化剂的中性或离子性质无关两亲的。
Chiral Rh phosphine–phosphite catalysts immobilized on ionic resins for the enantioselective hydrogenation of olefins in water
作者:P. Kleman、P. Barbaro、A. Pizzano
DOI:10.1039/c5gc00485c
日期:——
Rh phosphine–phosphite chiral catalysts immobilized on ion exchange resins provide highly enantioselective hydrogenation of enamides in water.
Practical Enantioselective Hydrogenation of α-Aryl- and α-Carboxyamidoethylenes by Rhodium(I)-{1,2-Bis[(<i>o</i>-<i>tert</i>-butoxyphenyl)(phenyl)phosphino]ethane}
作者:Barbara Mohar、Michel Stephan
DOI:10.1002/adsc.201200780
日期:——
The rhodium(I)-1,2-bis[(o-tert-butoxyphenyl)(phenyl)phosphino]ethane} [Rh(I)-(t-Bu-SMS-Phos)] catalyst system displayed prime efficiency in the hydrogenation of large series of α-amidostyrenes and α-amidoacrylates. Up to >99.9% enantiomeric excesses coupled with very high reaction rates were attained operating routinely under 1–10 bar of hydrogen at 22 °C in methanol. Examples include industrial substrates