1,3-Dipolar cycloaddition of unstabilised azomethine ylides by Lewis base catalysis

Lewis base catalysed 1,3-dipolar cycloaddition between alpha,beta-unsaturated acyl fluorides and N-[(trimethylsilyl)methyl]amino ethers has been achieved using 1 mol% DMAP. Competition experiments and F-19-NMR studies indicate that the cycloaddition occurs preferentially between the alpha,beta-unsaturated acyl fluoride and the unstabilised azomethine ylide. In addition, an enantioselective variant, using chiral isothiourea catalysts, has been achieved with 14% ee.