13325-12-7Relevant academic research and scientific papers
Synthesis via Isoxazolines, 5. - 1,3-Asymmetric Induction in the reduction of 3,5-Disubstituted 2-Isoxazolines; Diastereoselective Synthesis and Configurational Assignment of γ-Amino Alcohols
Jaeger, Volker,Buss, Volker
, p. 101 - 121 (2007/10/02)
The cycloaddition of nitrile oxides to alkenes, followed by reduction of the ensuing 2-isoxazolines 3, yields γ-amino alcohols 4 in a regioselective manner.The stereoselectivity of the reduction step is examined; it is highest with LiAlH4 as the reducing agent. 1,3-Asymmetric induction by isoxazoline ring substituents leads to β-4:α-4 ratios of ca. 85:15 for 5-methyl and ca. 95:5 for 5-phenyl. (CH3)2S-BH3, less selectively, furnishes 60:40, Na-Hg and Na/ethanol reduction give rise to 40:60 diastereomer mixtures.From these, two amino alcohols of the α-series are isolated. 3a is reduced by NaBH3CN to give cis/trans-isoxazolines 11. - The relative configurations of β- and α-4 and, consequently, the steric course of these reductions, are established by 1H- and 13C-NMR studies of 4 as well as of cyclic derivatives (azetidine 7, tetrahydro-1,3-oxazine 10).In addition, conformations of the free amino alcohols 4 are suggested on the basis of 13C-NMR data.
