196940-71-3Relevant academic research and scientific papers
(-)-sparteine-mediated asymmetric intramolecular carbolithiation of alkenes: Synthesis of enantiopure cyclopentanes with three consecutive stereogenic centers
Hoppe, Dieter,Weltering, Michael J.,Oestreich, Martin,Froehlich, Roland
, p. 1860 - 1877 (2007/10/03)
An asymmetric intramolecular carbolithiation reaction was developed by combining the (-)-sparteine-mediated enantiotopos-differentiating deprotonation and the anionic 5-exo-trig cyclization. Achiral 6-phenylhex-5- enyl carbamates were efficiently cyclized furnishing regio-, diastereo- (dr >99:1), and enantioselectively (er >98:2) 1,2-trans-substituted cyclopentanes. The intermediate primary benzylic lithium-carbanion pairs were - in spite of their configurative lability - diastercoselectively substituted by versatile electrophiles creating a third consecutive stereogenic center. Additionally, some 4-functionalized 6-phenylhex-5-enyl carbamates were also cyclized in high yield to provide enantiomerically pure cyclopentanes incorporating three adjacent stereogenic centers.
Synthesis of enantiomerically and diastereomerically pure cyclopentanols by asymmetric cyclocarbolithiation of 5-alkenyl carbamates
Woltering,Frohlich,Hoppe
, p. 1764 - 1766 (2007/10/03)
Three vicinal stereocenters are formed in the (-)-sparteine-induced cyclocarbolithiation of 6-phenyl-5-hexenyl carbamates. The anionic cyclization products can be trapped with various electrophiles (El) to provide enantiomerically pure cyclopentanol derivatives [Eq. (a); Cby = 2,2,4,4-tetramethl-1,3-oxazolidin-3-carboxylate].
