72443-72-2Relevant academic research and scientific papers
ASYMMETRIC REDUCTIONS OF PROPARGYL KETONESAN EFFECTIVE APPROACH TO THE SYNTHESIS OF OPTICALLY-ACTIVE COMPOUNDS
Midland, M. Mark,Tramontano, Alfonso,Kazubski, Aleksander,Graham, Richard S.,Tsai, David J. S.,Cardin, Daniel B.
, p. 1371 - 1380 (2007/10/02)
Propargyl ketones are readily reduced by the asymmetric reducing agent B-3-pinanyl-9-borabicyclo-nonane (Alpine-borane).The reagent prepared from (+)-α-pinene and 9-BBN provides the R enantiomer while the S enantiomer can be obtained from (-)-α-pinene.Alternatively the S enantiomer ca be prepared from the reagent derived from 9-BBn and the benzyl ether of nopol (6,6-dimethyl-bicyclohept-2-ene-2-ethanol).The limiting factor in obtaining high enantiomeric induction is often the enantiomeric purity of the α-pinene.With 100percent enantiomerically pure α-pinene, propargyl alcohols of essentially 100percent ee can be obtained.A predictive rationalization of the transition state leading to this remarkable selection is presented.The acetylene unit of the propargyl alcohol provides a convenient handle for transformations to other useful, optically-active products.The use of propargyl alcohols for the synthesis of optically-active α- and β-substituted γ-lactones, and δ-lactones is illustrated.
Asymmetric Reductions of α,β-Acetylenic Ketones and Acetophenone Using Lithium Aluminum Hydride Complexed with Optically Active 1,3-Amino Alcohols
Cohen, Noal,Lopresti, Rocco J.,Neukom, Christian,Saucy, Gabriel
, p. 582 - 588 (2007/10/02)
Asymmetric reduction of the α,β-acetylenic ketones 9a-f using the freshly prepared complex derived from LiAlH4 and (2S,3R)-(+)-4-(dimethylamino)-3-methyl-1,2-diphenyl-2-butanol (Darvon alcohol; 10) at -70 deg C gives mainly the (R)-carbinols 1a-f in yields of 62-99percent and enantiomeric excesses of 34-90percent.Similar treatment of 9e with the complex formed from LiAlH4 and 11, the enantiomer of 10, affords 2e, a useful intermediate for the synthesis of (2R,4'R,8'R)-α-tocopherol (vitamin E), in 96percent yield and 90percent ee.The optically pure 1,3-amino alcohol ligands 12-16, which are structurally related to 10, were prepared by starting from the known (S)-ether sulfonate 23 and its enantiomer.Reduction of 9a and acetophenone using the LiAlH4-12 complex gives an excess of the corresponding (S)-carbinols 2a (36percent ee) and 27 (60percent ee), respectively.
