A detailed study of the dialkylation of dianions derived from dihydroisoindigo
1 with enantiopure ditriflate
2 is reported. The LHMDS-mediatedprocess has been optimized to give
C2-symmetric product
3 with high selectivity (
C2 selectivity
3:
5 = 100:1;
C2:
C1 selectivity = 8:1).Stereoselection in the
C2 manifold is determined in both the bimolecular and intramolecular alkylation steps.