Stereospecific β-Lithiation of Oxazolinyloxiranes: Synthesis of α,β-Epoxy-γ-butyrolactones
摘要:
Stereospecific beta-lithlation of beta-aryl-substituted oxazollnyloxiranes is described. The trapping reaction of such reactive intermediates with carbonyl compounds gave alpha,beta-epoxy-gamma-butyrolactones after deblocking of the oxazoline moiety. This methodology has been also extended to the synthesis of optically active alpha,beta-epoxy-gamma-butyrolactones.
Stereospecific β-Lithiation of Oxazolinyloxiranes: Synthesis of α,β-Epoxy-γ-butyrolactones
摘要:
Stereospecific beta-lithlation of beta-aryl-substituted oxazollnyloxiranes is described. The trapping reaction of such reactive intermediates with carbonyl compounds gave alpha,beta-epoxy-gamma-butyrolactones after deblocking of the oxazoline moiety. This methodology has been also extended to the synthesis of optically active alpha,beta-epoxy-gamma-butyrolactones.
The α-lithiation reaction of opticallyactive oxazolinyloxiranes has been investigated. The trapping reaction with D2O, MeI and acetone affording substituted oxazolinyloxiranes proved that the corresponding lithiated species are configurationally unstable. A stereoconvergency was observed in the case of lithiation–deuteration sequence of two oxazolinyloxiranes.
The addition reaction of alpha-lithiated oxazolinyloxiranes to nitrones has been investigated. 1,5,9-Trioxa-8,10-diazadispiro[2.0.4.3]undecanes formed in a completely diastereoselective manner upon treatment of alpha-lithiated oxiranes with nitrones. The lithiation of optically active trans and cis-oxazolinyloxiranes followed by the addition of a nitrone resulted in the formation of the same dispirocyclic compound. An explanation for the observed stereoselectivity is provided. (C) 2003 Elsevier Ltd. All rights reserved.