Ni(<scp>ii</scp>)-Catalyzed vinylic C–H functionalization of 2-acetamido-3-arylacrylates to access isotetronic acids
作者:Biswajit Roy、Eshani Das、Avijit Roy、Dipakranjan Mal
DOI:10.1039/d0ob00557f
日期:——
reaction for the synthesis of 4-aryl-substituted isotetronic acids from 2-acetamido-3-arylacrylates via vinylic C-H functionalization is reported. The reaction proceeds through heteroatom guided electrophilic insertion of nickel to the vinylic double bond followed by annulation with dibromomethane. This unconventional route features cascade steps, sole product formation, multiple functional group tolerance
Monodentate Phosphoramidites: A Breakthrough in Rhodium-Catalysed Asymmetric Hydrogenation of Olefins
作者:Michel van den Berg、Adriaan J. Minnaard、Robert M. Haak、Michel Leeman、Ebe P. Schudde、Auke Meetsma、Ben L. Feringa、André H. M. de Vries、C. Elizabeth P. Maljaars、Charlotte E. Willans、David Hyett、Jeroen A. F. Boogers、Hubertus J. W. Henderickx、Johannes G. de Vries
DOI:10.1002/adsc.200390026
日期:2003.1
ligands for the rhodium-catalysed asymmetrichydrogenation of olefins. Very high enantioselectivities were obtained with MonoPhos (7a) the simplest member of this class, a ligand that is prepared in a single step from BINOL and HMPT. Turnover numbers up to 6000 have been obtained in the hydrogenation of dehydroamino acid derivatives. Enantioselectivities in the hydrogenation of dehydroamino acids are solvent
Design and Preparation of a Chiral Ligand Based on a Pseudorotaxane Skeleton: Application to Rhodium-Catalyzed Enantioselective Hydrogenation of Enamides
works as a chiral bidentate ligand having a phosphine moiety in an axle and a phosphite moiety in a wheel as two coordination sites and applied it successfully to the rhodium-catalyzedenantioselectivehydrogenation of enamides (up to 96% ee). To the best of our knowledge, this is the first successful example of the use of the pseudorotaxane molecule as a chiral ligand for homogeneous transition-metal-catalyzed
Synthesis and Application of Phosphinoferrocenylaminophosphine Ligands for Asymmetric Catalysis
作者:Neil W. Boaz、Elaine B. Mackenzie、Sheryl D. Debenham、Shannon E. Large、James A. Ponasik
DOI:10.1021/jo048312y
日期:2005.3.1
[GRAPHICS]A new class of bidentate ligands utilizing a phosphine-aminophosphine structure has been prepared on a ferrocenylethyl backbone in a straightforward and scalable fashion from acetylferrocene. The unique property of the alpha-ferrocenyl carbonium ion that allows the replacement of a variety of "leaving groups" with retention of configuration greatly facilitates the synthesis, and a number of ligands have been prepared by varying the nitrogen and phosphorus substituents on the aminophosphine. These readily prepared phosphinoferrocenylaminophosphines, known as BoPhoz ligands, show surprising hydrolytic and air stability, with no degradation after 3 years open to the air. The rhodium complexes of these ligands show exceedingly high enantioselectivities (generally >95% ee) and activities often in excess of 50 000 catalyst turnovers per hour for the asymmetric hydrogenation of a wide variety of dehydro-alpha-amino acid and itaconic acid derivatives. They also show high activity and good to excellent enantioselectivity for the hydrogenation of a number of alpha-ketoesters.
Highly Enantioselective Hydrogenation of Enamides and Itaconic Acid in Water in the Presence of Water-Soluble Rhodium(I) Catalyst and Sodium Dodecyl Sulfate
作者:Koji Yonehara、Kouichi Ohe、Sakae Uemura
DOI:10.1021/jo9912505
日期:1999.12.1
The water-soluble cationic Rh complexes, such as [Rh(alpha-D-glucopyranosyl-(1,1)-2,3-di-O-(diphenylphosphino)-alpha-D-glucopyranoside)(cod)]BF4 (1) and [Rh(beta-D-glucopyranosyl-(1,1)-2,3-di-O-(diphenylphosphino)-beta-D-glucopyranoside)(cod)]BF4 (2) bearing free hydroxy groups, are effective catalysts in the asymmetric hydrogenation of various enamides and itaconic acid (up to 99.9% ee) in water in the presence of sodium dodecyl sulfate (SDS) (7.5 x 10(-3) to 1.0 x 10(-1) M). The hydrogenation of methyl (Z)-alpha-acetamidocinnamate in water using the corresponding Rh complexes of triflate (6) and D-camphor-10-sulfonate (7), prepared separately, results in a formation of the product of the same enantioselectivity (48% ee), but the use of SDS can reduce the amount of the catalyst and improve the enantioselectivity to 81% ee. These results show that the counteranions do not directly influence the enantioselectivity. Although the effect of SDS on the enhancement of enantioselectivity remains speculative, the formation of micelle seems to play an important role in improving the enantioselectivity.