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Karl Anker Jørgensen

Organocatalytic Enantioselective Cycloaddition Reactions of Dienamines with Quinones

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  • Tore Johansen
  • ,
  • Clarisa Villegas
  • ,
  • Jesper Rune Bak, Denmark
  • Rebecca Davis, Denmark
  • K.A. Jørgensen
Highly selective organocatalytic [4+2]-cycloaddition reaction of dienamines with 1,4-benzo- and 1,4-naphthoquinones leading to optically active bicyclic and tricyclic products was reported. To demonstrate the scope of the reaction, different substituted 1,4-benzo- and 1,4-naphthoquinones were employed. They all reacted smoothly in the cycloaddition reaction with 3-methyl-2-butenal. When exchanging the methyl group with a benzyl group in the 1,4- naphthoquinones, the reaction was retarded and 20 mol% of catalyst was applied to give the products in 74 76% yield and 96% ee. In examining the energetics of all four pathways, it was calculated that the first addition step for the endo approaches are 4.0 4.5 kcalmol lower than those of the exo approaches. The quinone products are obtained in moderate to high yields ranging from 55 99% and in all examples excellent enantioselectivity was observed. Computational studies suggest an endo-selective reaction course, calculated to be approximately 4 kcalmol lower in energy than the exo-selective pathway.
Original languageEnglish
JournalChemistry: A European Journal
Pages (from-to)16518-16522
Number of pages5
Publication statusPublished - 2013

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