A ceric ammonium nitrate based oxidative cleavage pathway for the asymmetric aldol adducts of oxadiazinones derived from (1 R ,2 S )- N - p -methoxybenzylnorephedrine
作者:Austin R. Leise、Nicole Comas、Doug Harrison、Dipak Patel、Eileen G. Whitemiller、Jennifer Wilson、Jacob Timms、Ian Golightly、Christopher G. Hamaker、Shawn R. Hitchcock
DOI:10.1016/j.tetasy.2017.08.003
日期:2017.9
An N-4-p-methoxybenzyloxadiazinone has been prepared from (1R,2S)-norephedrine through a process of reductive amination, N-nitrosation, reduction, and cyclization. The oxadiazinone was acylated and employed in the asymmetric aldol addition reaction with aromatic and aliphatic aldehydes to yield aldol adducts in isolated yields ranging from 54% to 90%. Selected aldol adducts were treated with ceric ammonium nitrate in aqueous acetonitrile to afford the desired beta-hydroxycarboxylic acids through a tandem process of oxidative cleavage of the N-4-p-methoxybenzyl group and acidic hydrolysis of the N-3-acyl side chain. The beta-hydroxycarboxylic acids were recovered in high diastereomeric purity as determined by 500 MHz H-1 NMR spectroscopy and the absolute configuration was confirmed by polarimetry. The chiral auxiliary unit, the 3,4,5,6-tetrahydro-2H-1,3,4-oxadiazin-2-one (oxadiazinone), was converted into its corresponding 3,6-dihydro-2H-1,3,4-oxadiazin-2-one (oxadiazinone) through an oxidative pathway promoted by the ceric ammonium nitrate. (C) 2017 Elsevier Ltd. All rights reserved.