Design of <i>N</i>-Spiro <i>C</i><sub>2</sub>-Symmetric Chiral Quaternary Ammonium Bromides as Novel Chiral Phase-Transfer Catalysts: Synthesis and Application to Practical Asymmetric Synthesis of α-Amino Acids
作者:Takashi Ooi、Minoru Kameda、Keiji Maruoka
DOI:10.1021/ja021244h
日期:2003.4.1
C(2)-symmetric chiralquaternaryammonium bromides 10 and 11 have been designed as a new, purely synthetic chiral phase-transfer catalyst, and readily prepared from commercially available optically pure 1,1'-bi-2-naphthol as a basic chiral unit. The details of the synthetic procedures of each requisite chiral binaphthyl subunit have been disclosed, and the structures of the assembled N-spiro chiral quaternary
9-Amino-(9-deoxy)cinchona alkaloid-derived new chiral phase-transfer catalysts
作者:Wenwen Peng、Jingwei Wan、Bing Xie、Xuebing Ma
DOI:10.1039/c4ob01648c
日期:——
9-amino-(9-deoxy)cinchona alkaloid-derived chiralphase-transfercatalysts bearing amino groups was developed by using known cinchona alkaloids as the starting materials. Due to the transformation of the 9-hydroxyl group into a 9-amino functional group, the catalytic performances were significantly improved in comparison with the corresponding first generation phase-transfercatalysts, and excellent yields (92–99%)
alkylation of the glycine imino ester 1a has been developed using a chiral quaternary ammonium salt 3d without chiral phosphine ligands. The proper choice of the achiral Pd ligand, P(OPh)3, is important to achieve high enantioselectivity. By this method with the dual catalysts, numerous enantiomerically enriched alpha-allylic amino acids 4a-h could be prepared with comparable to higher enantioselectivity
A new asymmetric two-center phase-transfercatalyst was designed and a catalyst library containing more than 40 new two-center catalysts was constructed. The catalysts were applied in phase-transferalkylations and Michael additions to afford the corresponding products in up to 93% ee and 82% ee, respectively.
We developed a versatile synthetic process for aeruginosin 298-A as well as several attractive analogues, in which all stereocenters were controlled by a catalytic asymmetric phase-transfer reaction and epoxidation. Furthermore, drastic counteranion effects in phase-transfer catalysis were observed for the first time, making it possible to three-dimensionally fine-tune the catalyst (ketal part, aromatic