Chiral aminoalcohols with a menthane skeleton as catalysts for the enantioselective addition of diethylzinc to benzaldehyde
摘要:
Novel chiral aminoalcohols were synthesized by highly diastereoselective addition of Me3SiCN and LICH2CN to (-)-menthone followed by LiAlH4 reduction. The addition of CH2=CH-MgBr and PhCH=CH-MgBr to menthone and the following epoxidation, provided useful hydroxy epoxides, one of which could be aminolyzed to afford an aminodiol. In one case, the configuration of the newly formed epoxidic stereogenic center was determined by X-ray crystallography. When applied as catalysts in the enantioselective addition of Et2Zn to benzaldehyde, the aminoalcohols induced enantiomeric excesses (e.e.s) of up to 77%. (C) 2001 Elsevier Science Ltd. All rights reserved.
New chiral iodooxazoline catalysts for the I(III)-mediated α-tosyloxylation of ketones: refining the stereoinduction model
摘要:
A new family of iodooxazoline catalysts, derived from widely available chiral ketones (menthone and camphor), was developed to promote the iodine(III)-mediated alpha-tosyloxylation of ketone derivatives. The reaction conditions to achieve the direct formation of the oxazoline moieties from the corresponding aminoalcohols and an aldehyde were explored and optimized. These catalysts were tested for the alpha-tosyloxylation of propiophenone and led to new information on the stereoinduction process. The results demonstrate that modulation of the steric hindrance around the iodane center is critical to obtain good activity. Additionally, from the selectivities observed, a preliminary predictive model is proposed. (C) 2013 Elsevier Ltd. All rights reserved.