Titanium-catalyzed enantioselective additions of alkyl groups to aldehydes: mechanistic studies and new concepts in asymmetric catalysis.
The catalytic asymmetric addition of alkyl groups to aldehydes is an important reaction in the enantioselective synthesis of secondary alcohols. This reaction can be catalyzed by zinc- or titanium-based catalysts. While the mechanism of the zinc/amino alcohol catalysts has received significant attention, the titanium-based catalysts have been less studied. This Account summarizes our mechanistic studies with bis(sulfonamide) and BINOL-derived titanium catalysts. It also describes our use of this reaction in the development of new approaches to asymmetric catalysis, including applications of diastereomeric catalysts and optimization of asymmetric catalysts with achiral and meso ligands.
University of Pennsylvania, Department of Chemistry, 231 South 34th Street, Philadelphia, Pennsylvania 19104-6323. pwalsh@sas.upenn.edu
Patrick J
PJ
Walsh
D000438:Alcohols / Q000737:chemistry; D000447:Aldehydes / Q000138:chemical synthesis*; D000478:Alkylation; D002384:Catalysis; D008024:Ligands; D008956:Models, Chemical; D015394:Molecular Structure; D009284:Naphthols / Q000737:chemistry; D009942:Organometallic Compounds / Q000138:chemical synthesis; D013237:Stereoisomerism; D013449:Sulfonamides / Q000138:chemical synthesis / Q000737:chemistry; D014025:Titanium / Q000737:chemistry*; D015032:Zinc / Q000737:chemistry
D000438:Alcohols; D000447:Aldehydes; C406944:BINOL, naphthol; D008024:Ligands; D009284:Naphthols; D009942:Organometallic Compounds; D013449:Sulfonamides; C059688:alkoxyl radical; D014025:Titanium; D015032:Zinc