Photochemical Deracemization of Allenes and Subsequent Chirality Transfer

Manuel Plaza, Christian Jandl, Thorsten Bach

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Trisubstituted allenes with a 3-(1′-alkenylidene)-pyrrolidin-2-one motif were successfully deracemized (13 examples, 86–98 % ee) employing visible light (λ=420 nm) and a chiral triplet sensitizer as the catalyst (2.5 mol %). The photocatalyst likely operates by selective recognition of one allene enantiomer via hydrogen bonds and by a triplet-sensitized racemization process. Even a tetrasubstituted allene (45 % ee) and a seven-membered 3-(1′-alkenylidene)-azepan-2-one (62 % ee) could be enantiomerically enriched under the chosen conditions. It was shown that the axial chirality of the allenes can be converted into point chirality by a Diels–Alder (94–97 % ee) or a bromination reaction (91 % ee). Ring opening of the five-membered pyrrolidin-2-one was achieved without significantly compromising the integrity of the chirality axis (92 % ee).

Original languageEnglish
Pages (from-to)12785-12788
Number of pages4
JournalAngewandte Chemie International Edition in English
Issue number31
StatePublished - 27 Jul 2020


  • allenes
  • chiral resolution
  • enantioselectivity
  • hydrogen bonds
  • photochemistry
  • sensitizers


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