Systematic studies using 2-(1-adamantylethynyl)pyrimidine-5-carbaldehyde as a starting material in Soai's asymmetric autocatalysis.
Herein, we present a new substrate for the Soai reaction, which has an adamantylethynyl residue (1 g) and exhibits asymmetric autocatalysis, yielding products with enantiomeric excesses above 99%. For the first time, all reactions were performed on a parallel synthesizer system to ensure identical reaction conditions. A detailed systematic study of reaction parameters was performed and we report the highest enhancements of enantiomeric excess reported so far in the Soai reaction in one reaction cycle (7.2-->94.1% ee or 3.1-->92.1% ee). Our results led to a set of reaction parameters that yield reproducible results. Therefore, our new starting material 1 g is suitable for systematic and mechanistic studies on this remarkable reaction. A series of experiments designed to quantify the amplification of enantiomeric excess demonstrated that the reaction can be used in principle as a tool for the detection of low enantiomeric excesses: under definite conditions, an unknown low enantiomeric excess (0.1-7%) was amplified to a detectable one. A back calculation to the original value offers a new method for the determination of small enantiomeric excesses.
Busch
Mark
M
Institut für Organische Chemie, Universität Karlsruhe (TH), Karlsruher Institut für Technologie (KIT), Fritz-Haber-Weg 6, 76131 Karlsruhe, Germany.
Schlageter
Martin
M
Weingand
Daniel
D
Gehring
Timo
T
D000218:Adamantane / Q000031:analogs & derivatives* / Q000737:chemistry; D000447:Aldehydes / Q000737:chemistry*; D002384:Catalysis; D007202:Indicators and Reagents / Q000737:chemistry; D008958:Models, Molecular; D013237:Stereoisomerism; D015032:Zinc / Q000737:chemistry
C543626:2-(1-adamantylethynyl)pyrimidine-5-carbaldehyde; D000447:Aldehydes; D007202:Indicators and Reagents; D015032:Zinc; D000218:Adamantane