摘要:
An efficient asymmetric synthesis of alpha-(1,1-dioxo-2,3-dihydro-1H-1lambda(6)-benzo[b]thiophen-2-yl)-substituted amines is described. Key steps of the synthesis are the nucleophilic 1,2-addition of 2-lithio-benzo[b]thiophene to aldehyde-SAMP-hydrazones, a benzo[b]thiophene oxidation using dimethyldioxirane and a highly diastereoselective conjugate reduction with L-Selectride(R). The heterocyclic beta-aminosulfones are obtained in five steps and good overall yields (23-49%) and very high diastereo-and enantiomeric excesses (de greater than or equal to 96%, ee = 88-99%).