Enantioselective carbonyl reverse prenylation from the alcohol or aldehyde oxidation level employing 1,1-dimethylallene as the prenyl donor

J Am Chem Soc. 2009 May 27;131(20):6916-7. doi: 10.1021/ja902437k.

Abstract

Enantioselective transfer hydrogenation of 1,1-dimethylallene 1a in the presence of aromatic, alpha,beta-unsaturated, or aliphatic aldehydes 2a-i mediated by 2-propanol and employing a cyclometalated iridium C,O-benzoate derived from allyl acetate, m-nitrobenzoic acid, and (S)-SEGPHOS delivers reverse-prenylation products 4a-i in good to excellent isolated yields (65-96%) and enantioselectivities (87-93% ee). In the absence of 2-propanol, enantioselective carbonyl reverse prenylation is achieved directly from the alcohol oxidation level to furnish an equivalent set of adducts 4a-i in good to excellent isolated yields (68-94%) and enantioselectivities (86-91% ee). Competition and isotopic labeling experiments suggest rapid alcohol-aldehyde redox equilibration in advance of carbonyl addition along with capture of the kinetically formed pi-allyl complex at a higher rate than reversible beta-hydride elimination-hydrometalation. This protocol represents an alternative to the use of allylmetal reagents in enantioselective carbonyl reverse prenylation and represents the first use of allenes in enantioselective C-C bond-forming transfer hydrogenation.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alcohols / chemical synthesis*
  • Alcohols / chemistry
  • Aldehydes / chemistry*
  • Alkadienes / chemistry*
  • Alkenes / chemical synthesis*
  • Alkenes / chemistry
  • Benzoates / chemistry
  • Catalysis
  • Iridium / chemistry
  • Organometallic Compounds / chemistry
  • Oxidation-Reduction
  • Phosphines / chemistry
  • Prenylation
  • Stereoisomerism

Substances

  • Alcohols
  • Aldehydes
  • Alkadienes
  • Alkenes
  • Benzoates
  • Organometallic Compounds
  • Phosphines
  • Iridium
  • propadiene