Organocatalytic Asymmetric 1,6‐Addition/1,4‐Addition Sequence to 2,4‐Dienals for the Synthesis of Chiral Chromans |
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| Authors: | Pernille H. Poulsen Karla Santos Feu Bruno Matos Paz Prof. Dr. Frank Jensen Prof. Dr. Karl Anker Jørgensen |
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| Affiliation: | Department of Chemistry, Aarhus University, 8000 Aarhus C (Denmark) |
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| Abstract: | A novel asymmetric organocatalytic 1,6‐addition/1,4‐addition sequence to 2,4‐dienals is described. Based on a 1,6‐Friedel–Crafts/1,4‐oxa‐Michael cascade, the organocatalyst directs the reaction of hydroxyarenes with a vinylogous iminium‐ion intermediate to give only one out of four possible regioisomers, thus providing optically active chromans in high yields and 94–99 % ee. Furthermore, several transformations are presented, including the formation of an optically active macrocyclic lactam. Finally, the mechanism for the novel reaction is discussed based on computational studies. |
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| Keywords: | asymmetric synthesis heterocycles Michael addition organocatalysis synthetic methods |
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