Baylis-Hillman bromides have been successfully employed as a valuable source of 1,3-dipoles for cycloaddition onto dialkyl azodicarboxylates (dipolarophiles) under the influence of dimethyl sulfide and potassium carbonate to provide functionalized dihydropyrazole derivatives in a simple one-pot [3+2] annulation strategy.
Nitroallylic acetates 1a-f have been kinetically resolved via an asymmetric three-component coupling that involves indoles, acrolein, and nitroolefin allylic acetates and is mediated by the chiral catalyst 2 (5 mol %). The reactions proceed via iminium/enamine cascade catalysis. Both recovered starting substrates and reaction products are typically obtained in high chemical yield and in good to excellent enantiopurity (79-95% ee for 1a-f and 83-99% ee for 3a-n). For the first time, a highly efficient three-component, organocascade kinetic resolution has been demonstrated.
This study describes an organocatalytic kinetic resolution of racemic secondary nitroallylic alcohols (2) combined with simultaneous desymmetrization of prochiral cyclic anhydrides (1). The experimental results revealed that enantioselective alcoholysis of 3-substituted glutaric anhydrides afforded hemiesters (3) with high levels of enantioselectivities (up to 99% ee) in the presence of cinchonidine-derived thiourea catalyst (IV). The highly optical enrichment (up to 95% ee) of (S)-nitroallylic alcohols (2) was recovered.
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