105074-56-4Relevant academic research and scientific papers
Atropselective Dibrominations of a 1,1′-Disubstituted 2,2′-Biindolyl with Diverging Point-to-Axial Asymmetric Inductions. Deriving 2,2′-Biindolyl-3,3′-diphosphane Ligands for Asymmetric Catalysis
Baumann, Thomas,Brückner, Reinhard
supporting information, p. 4714 - 4719 (2019/03/26)
On the 1H NMR timescale, 2,2′-biindolyls with (R)-configured (1-alkoxyprop)-2-yl, (1-hydroxyprop)-2-yl, or (1-siloxyprop)-2-yl substituents at C-1 and C-1′ are atropisomerically stable at 30 °C. A 2,2′-biindolyl (R,R)-17 a of that kind and achiral (!) brominating reagents gave the atropisomerically stable 3,3′-dibromobiindolyls (M)- and/or (P)-18 a at best atropselectively—because of point-to-axial asymmetric inductions—and atropdivergently, exhibiting up to 95 % (M)- and as much (P)-atropselectivity. This route to atropisomerically pure biaryls is novel and should extend to other substrates and/or different functionalizations. The dibromobiindolyls (M)- and (P)-18 a furnished the biindolyldiphosphanes (M)- and (P)-14 without atropisomerization. These syntheses did not require the resolution of a racemic mixture, which distinguishes them from virtually all biaryldiphosphane syntheses known to date. (M)- and (P)-14 acted as ligands in catalytic asymmetric allylations and hydrogenations. Remarkably, the β-ketoester rac-25 c was hydrogenated trans-selectively with 98 % ee; this included a dynamic kinetic resolution.
Studies of Chiral Indoles. Part I. Indoles with Chiral 1- and 3-Substituents. Synthesis and Preparative Enantiomeric Separation by Chromatography on Microcrystalline Triacetylcellulose
Nilsson, Ingemar,Isaksson, Roland
, p. 531 - 548 (2007/10/02)
A number of indole derivatives with chiral substituents in position 1 or 3 and with substituents of varying size in position 2 have been prepared.The chiral rotors are 1-N,N-dimethylcarbamoylethyl and N'-methylpiperidin-2'-on-3'-yl and their corresponding thioanalogues, and 1-phenylethyl.The reaction conditions required to obtain preferential 1- or 3-alkylation are discussed in terms of the HSAB principle and the extent of ion pair formation.Three 1-(N,N-dimethylcarbamoylethyl-indoles (R2=H and Me, and R2=Me, R3=CO2Me, R5=OMe) and one 1-(1-phenylethyl)indole (R2=Me, R3=CO2Me, R5=OMe) were obtained optically pure by stereospecific pathways.The other compounds were obtained in racemic forms.Most of the racemic compounds were conveniently resolved by liquid chromatography on swollen, microcrystalline triacetylcellulose (TAC).In some cases rather remarkable separations were obtained.Attempts were made to prepare the optically active 1- and 3-(N'-methylpiperidin-2'-on-3'-yl)indoles by hydrolysis of the methylthioimmonium salts prepared from chromatographically resolved thioamides.The 3-substituted analogues were partly racemized in this process, while the 1-substituted ones were completely racemized.A possible explanation is proposed.
