Substrate-controlled reactions have been developed for the synthesis of spirocyclopropylpyrazolones and bicyclic 4,5-dihydropyrazoles from 1,2-diaza-1,3-dienes and sulfur ylides. These protocols were carried out under mild reaction conditions without any additives in generally moderate to good yields. Plausible mechanisms for the transformations were proposed.
Batting the ylides: A simple procedure carried out under mild conditions allows the direct and efficientsynthesis of structurally diverse indoles. This approach involves a cascadereaction of sulfurylides and N‐(ortho‐chloromethyl)arylamides (see scheme).
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
A novel organocatalytic asymmetric cyclopropanation of beta,gamma-unsaturated alpha-ketoesters with stabilized sulfur ylides using C-2-symmetric urea as a hydrogen-bond catalyst has been described. This reaction allows an efficient access to 1,2,3-trisubstituted cyclopropane derivatives in moderate to good yields with up to 16:1 dr and 90: I 0 er under mild reaction conditions. The mechanism study proved that the high stereoinduction originated from the cooperative effect of the hydrogen-bond catalyst.