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Polycyclic molecules and tetrahydroquinoleines were obtained in a tandem reaction involving the diastereoselective addition of alpha-aminoalkyl radicals to (5R)-5-menthyloxy-2[5H]-furanone 1. The facial diastereoselectivity on 1 is >/=90%. The alpha-aminoalkyl radicals were produced from tertiary amines by photochemical-induced electron transfer. When N,N-dialkylanilines 19 were used as starting tertiary amines, a rearomatization step was involved and important side reactions of 1 were observed. A mechanistic study involving isotopic labeling of the starting amine indicated that the byproducts resulted from reduction of 1 during the rearomatization process. An efficient optimization of the reaction was obtained by simply adding acetone or cyclopentanone as mild oxidants to the reaction mixture. The side products resulting from reduction of the furanone 1 were completely suppressed under these conditions, and the yields of the tetrahydroquinolines 21a-i, 22a-f, and 26g-i were doubled.

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The radical tandem reaction of simple alkyl derivatives of aniline to a chiral furanone can be carried out stereoselectively in high yields; the furanone is also involved as oxidant in a rearomatisation process (formation of byproducts) where it can be replaced efficiently by acetone.