248923-50-4Relevant academic research and scientific papers
trans-3,4-Disubstituted pyrrolidines by 1,3-dipolar cycloaddition: Enantioselective approaches and their limitations
Karlsson, Staffan,Han, Fusen,Hoegberg, Hans-Erik,Caldirola, Patrizia
, p. 2605 - 2616 (2007/10/03)
In the presence of a chiral Lewis acid as co-catalyst, the acid- catalysed 1,3-dipolar cycloaddition reaction yielding trans-3,4-disubstituted pyrrolidines from an azomethine ylide and achiral α,β-unsaturated dipolarophiles proceeded with low enantioselectivity. Therefore a number of α,β-unsaturated dipolarophiles linked to chiral auxiliaries were examined as substrates. Camphorsultam was the best auxiliary and gave good diastereoselectivity (dr=74:26). When combining chiral Lewis acids with a dipolarophile linked to a chiral auxiliary, the enantio-selectivity could be slightly increased. As judged by 13C NMR, the small effect of the chiral Lewis acids on selectivity was probably due to breakdown of the initially formed complex with the dipolarophile caused by the dipole precursor.
