Chiral phosphoric acid-catalyzed Friedel–Crafts reaction of 2,5-disubstituted and 2-monosubstituted pyrroles with isoindolinone-derived ketimines†
The enantioselective reaction between 2,5-disubstituted pyrroles and diaryl-ketimines, generated in situ from isoindolinone-derived alcohols, is described. Pyrrole derivatives possessing a congested tetrasubstituted stereogenic center at the β-(C3) position are generally obtained in high yields and enantioselectivities. The transformation can be extended to 2-monosubstituted pyrroles, generating chiral α-(C5) functionalized pyrrole products. Control experiments were conducted in order to elucidate the origin of the low enantioselectivities observed in some of the products.