| Abstrakt: |
We report a visible‐light‐mediated organocatalytic strategy for the enantioselective acyl radical conjugate addition to enals, leading to valuable 1,4‐dicarbonyl compounds. The process capitalizes upon the excited‐state reactivity of 4‐acyl‐1,4‐dihydropyridines that, upon visible‐light absorption, can trigger the generation of acyl radicals. By means of a chiral amine catalyst, iminium ion activation of enals ensures a stereoselective radical trap. We also demonstrate how the combination of this acylation process with a second catalyst‐controlled bond‐forming event allows to selectively access the full matrix of all possible stereoisomers of the resulting 2,3‐substituted 1,4‐dicarbonyl products. A 1,4 relation problem: Chiral 1,4‐dicarbonyls are important motifs, but their stereocontrolled synthesis is difficult. A photochemical asymmetric acyl radical addition to enals 2 is presented as one solution to this problem. This enantioselective catalytic strategy is triggered by iminium ion activation. It exploits the visible‐light excitation of 4‐acyl‐1,4‐dihydropyridines 1 to generate acyl radicals under mild conditions. [ABSTRACT FROM AUTHOR] |
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