Bicyclo[2.2.2]octane-derived chiral ligands—synthesis and application of BODOLs in the asymmetric reduction of acetophenone with catecholborane
摘要:
An improved synthetic route to the bicyclo[2.2.2]octane-2,6-diol ligands (2,6-BODOLS) allowed an increased structural variation of the ligand side-arm. The addition of aromatic or vinylic Grignard reagents to hydroxyketone 1 was highly selective and ligands 3f-3I were isolated in 84-97% yield. The addition of alkyl Grignard reagents containing beta-hydrogens resulted in lower yields (13-71%) due to competing ketone reduction. A number of 2,5-BODOLs were synthesized using a similar methodology. The ligands, together with Ti(OiPr)(4), were tested in the asymmetric reduction of acetophenone with catecholborane (up to 98% ee). 1-Naphthyl-BODOL 3i was employed as an allylboration reagent to benzaldehyde together with Sc(OTf)(3), resulting in (1S)-1-phenyl-3-buten-1-ol in 80% ee. (C) 2008 Elsevier Ltd. All rights reserved.
Bicyclo[2.2.2]octane-derived chiral ligands—synthesis and application of BODOLs in the asymmetric reduction of acetophenone with catecholborane
摘要:
An improved synthetic route to the bicyclo[2.2.2]octane-2,6-diol ligands (2,6-BODOLS) allowed an increased structural variation of the ligand side-arm. The addition of aromatic or vinylic Grignard reagents to hydroxyketone 1 was highly selective and ligands 3f-3I were isolated in 84-97% yield. The addition of alkyl Grignard reagents containing beta-hydrogens resulted in lower yields (13-71%) due to competing ketone reduction. A number of 2,5-BODOLs were synthesized using a similar methodology. The ligands, together with Ti(OiPr)(4), were tested in the asymmetric reduction of acetophenone with catecholborane (up to 98% ee). 1-Naphthyl-BODOL 3i was employed as an allylboration reagent to benzaldehyde together with Sc(OTf)(3), resulting in (1S)-1-phenyl-3-buten-1-ol in 80% ee. (C) 2008 Elsevier Ltd. All rights reserved.
New bicyclic γ- and δ-aminoalcohols as catalysts for the asymmetric diethylzinc addition to benzaldehyde
作者:Cecilia Olsson、Sara Helgesson、Torbjörn Frejd
DOI:10.1016/j.tetasy.2008.06.002
日期:2008.6
A newclass of chiral non-racemic γ- and δ-amino alcohols based on bicyclo[2.2.1]heptane and bicyclo[2.2.2]octane have been synthesized and used as catalysts in the asymmetric diethylzinc addition to benzaldehyde.