Amino Alcohol Screening and Optimization of the Diethylzinc Reaction

January 08, 2024

• Title:       

  Amino Alcohol Screening and Optimization of the  Diethylzinc Reaction 

• Image Source:

  Dual stereoselectivity in the dialkylzinc reaction using (-)-β-pinene derived amino alcohol chiral auxiliaries

• Figure Mark:

  Table1

• Associated context:

  We were surprised to find that the 2:1 cis/trans mixture of  amino alcohols obtained from the sodium borohydride reduction  of R-amino ketone 6 gave results comparable to those of pure  2-MAP in the diethylzinc reaction (Table 1, entry 9). This  suggests that diastereomeric purity of the ligand was not crucial  for obtaining secondary alcohol products in high enantiomeric  excess. Intrigued by this finding, we set out to further investigate  the apparent asymmetric amplification in mixtures of these cis/ trans diastereomers using the optimized conditions. Spiking the  transamino alcohol 2 with only 19% of 2-MAP increases the  % ee from 71% to 89% (Figure 5).