Reactions of Nitroalkenes with Nitroalkanes or Sulfur Ylides Catalyzed by Amine-Thiourea Bifunctional Polymeric Organocatalysts
作者:Patrick Toy、Jinni Lu
DOI:10.1055/s-0031-1289900
日期:2011.12
Non-cross-linked and cross-linked bifunctional polystyrenes bearing both amine and thiourea groups have been synthesized and used as organocatalysts in reactions between nitroalkenes and nitroalkanes or sulfur ylides. Control experiments using monofunctional polymers with only either amine or thiourea groups attached indicated that both functional groups were essential for efficient catalysis of the reactions studied. The non-cross-linked polystyrene was soluble in typical organic solvents and was used as a homogeneous catalyst, while the cross-linked polystyrene was used as a heterogeneous catalyst.
Moreover, this strategy was also successfully applied to the asymmetric [4 + 1]/[3 + 2] cycloadditioncascade of sulfurylides with alkene-tethered nitroolefins, and the corresponding enantioenriched fused heterocycles (up to 87:13 e.r. and >95:5 d.r.) were obtained in good to excellent yields (54–95% yields).
A regio- and stereoselectivesynthesis of functionalized 4,5-disubstituted oxazolidin-2-ones is reported with moderate to good yields from the reaction of α-epoxyketones with urea in the presence of p -toluenesulfonic acid as the catalyst.
A hydrogen‐bond‐mediated asymmetric [4+1] annulation/rearrangement cascade of stable sulfur ylides and nitroolefins was developed. This reaction provides a facile route to enantioenriched 4,5‐substituted oxazolidinones in moderate to excellent isolated yields (65–96 %) with excellent stereocontrol (up to more than 95:5 d.r. and 97:3 e.r.). This methodology was successfully applied to the concise synthesis