Chemistry: A European Journal
Sebastijan Ričko, Joseph Izzo, Karl Anker Jørgensen
The use of pseudo enantiomers is a well‐known method of achieving products of complementary stereochemistry. Only rarely can different enantiomers of a product be accessed without modulation of the catalyst. Recently, a system was reported wherein two different enantiomers of spirocycles were obtained by a cascade reaction of unsaturated pyrrolin‐4‐ones with mercaptoacetaldehyde catalyzed by a single optimized cinchona alkaloid squaramide‐derived organocatalyst. It was originally proposed that the E/Z geometry of the unsaturated pyrrolin‐4‐one dictated the stereochemistry of the spirocycle product, but this was not investigated further. In the present work, we have investigated the nature of a pseudo‐enantiomeric organocatalyst conformation applying density functional theory calculations for investigating the transition states for the reaction. Furthermore, the influence of the double‐bond geometry of the pyrrolin‐4‐one has been studied beyond what is possible to test experimentally. The results provide a greater understanding for this class of reactions that may be applicable in future methodology development.
Read article: Chem. Eur. J., 2020, 15727-15732
