Catalytic Asymmetric Synthesis of Chiral 2-Vinylindole Scaffolds by Friedel-Crafts Reaction.

A chiral bis(imidazolidine)pyridine (PyBidine)-Ni(OTf)2 complex smoothly catalyzed an asymmetric Friedel-Crafts reaction of 2-vinylindoles with nitroalkenes to give chiral indoles in a highly enantioselective manner while maintaining the 2-vinyl functionality. The chiral 2-vinylindoles offer unique chiral scaffolds for diverse transformations.

PyBidine-Ni(OAc)2-Catalyzed Michael/Aldol Reaction of Methyleneindolinones and Thiosalicylaldehydes for Stereochemically Divergent Thiochromanyl-spirooxindoles.

(S,S)-Diphenylethylenediamine-derived bis(imidazolidine)pyridine (PyBidine)-Ni(OAc)2 complex catalyzed the asymmetric Michael/aldol reaction of methyleneindolinone and thiosalicylaldehyde to produce (2'R,3S,4'R)-thiochromanyl-spirooxindole having three contiguous stereogenic centers.

Catalytic asymmetric [3 + 2]-cycloaddition for stereodivergent synthesis of chiral indolyl-pyrrolidines.

The stereochemical divergent synthesis of indolyl-pyrrolidines was accomplished using an imidazoline-aminophenol (IAP)-Ni(OAc)2 complex and a bis(imidazolidine)pyridine (PyBidine)-Cu(OTf)2 complex. The former catalyzed exo'-selective asymmetric [3 + 2] cyclization of iminoesters with indolyl nitroalkenes, and the latter catalyzed the reaction in an endo-selective manner. These catalysts are tolerant toward highly functional substrates that supply chiral indolyl-pyrrolidine hybrids.

Synthesis of Highly Functionalized Chiral Benzopyrano[3,4-c]pyrrolidines Bearing Five Contiguous Stereogenic Centers.

A chiral bis(imidazolidine)pyridine-Cu complex smoothly catalyzed the asymmetric [3 + 2] cycloaddition reaction of α,ß-unsaturated ester-containing nitroalkenes with imino esters to give endo-pyrrolidine products in a highly enantioselective manner while maintaining the α,ß-unsaturated ester functionality. Subsequent intramolecular diastereoselective cyclizations of the obtained pyrrolidine products were accomplished by treatment with KF/Al2O3 in toluene/EtOH (4:1) to give highly functionalized benzopyrano[3,4-c]pyrrolidines bearing five contiguous stereogenic centers.