Asymmetric addition of diethylzinc to benzaldehyde catalyzed by novel chiral C2-symmetric tetrakis(sulfonamide)–titanium(IV) complexes
摘要:
A series of chiral C-2-symmetric tetrakis(sulfonamides) 3a-f, 4a-f were prepared and employed as ligands for titanium(IV) complexes in the asymmetric addition of diethylzinc to benzaldehyde. The chiral secondary alcohols were obtained in high yields and in moderate enantioselectivities. (C) 2010 Elsevier Ltd. All rights reserved.
Synthesis of homochiral pentadentate sulfonamide-based ligands
摘要:
A two-step synthesis of pentadentate, tetraionic ligands based on sulfonamide, amide, and pyridyl groups is reported. These ligands are easily accessible in good to excellent yield from commercially available materials. (C) 2001 Elsevier Science Ltd. All rights reserved.
accessible tridentate ferrocene-based diamine-phosphine sulfonamide (f-diaphos) ligands were successfully developed for iridium-catalyzedasymmetrichydrogenation of ketones. The f-diaphos ligands exhibited excellent enantioselectivity and superb reactivity in Ir-catalyzed asymmetrichydrogenation of ketones (for arylalkyl ketones, (S)-selectivity, up to 99.4% ee, and 100 000 TON; for diaryl ketones, (R)-selectivity
This work disclosed a highly enantioselective hydrogenation of non-ortho-substituted 2-pyridyl arylketones via Ir/f-diaphos catalysis. This catalytic system allows for full control over the configuration of the stereocenter, affording two enantiomers of the desired products with extremely high enantioselectivity (up to >99% ee in most cases) and excellent reactivity (TON of up to 19600, TOF of 1633
The iridium/f-diaphos L1, L5 or L12 catalyzed asymmetric hydrogenation of 2-imidazolyl aryl/alkyl ketones to afford two enantiomers of the desired chiral alcohols with high conversions (up to 99% yield) and moderate to excellent enantioselectivities (61% - >99% ee) was realized for the first time. This protocol could be easily conducted on a gram-scale with a TON of 9700.
铱/ f-二磷L1、L5或L12催化 2-咪唑基芳基/烷基酮的不对称氢化,得到所需手性醇的两种对映异构体,具有高转化率(高达 99% 的产率)和中等至优异的对映选择性(61% - >99% ee ) 首次实现。该协议可以在 TON 为 9700 的克级上轻松执行。