title: Preparation and reactions of enantiomerically pure α-functionalized Grignard reagents.
abstract: A strategy for the generation of enantiomerically pure α-functionalized chiral Grignard reagents is presented. The approach involves the synthesis of α-alkoxy and α-amino sulfoxides in ≥99:1 dr and ≥99:1 er via asymmetric deprotonation (s-BuLi/chiral diamine) and trapping with Andersen's sulfinate (menthol derived). Subsequent sulfoxide → Mg exchange (room temperature, 1 min) and electrophilic trapping delivers a range of enantiomerically pure α-alkoxy and α-amino substituted products. Using this approach, either enantiomer of products can be accessed in 99:1 er from asymmetric deprotonation protocols without the use of (-)-sparteine as the chiral ligand. Two additional discoveries are noteworthy: (i) for the deprotonation and trapping with Andersen's sulfinate, there is a lack of stereospecificity at sulfur due to attack of a lithiated intermediate onto the α-alkoxy and α-amino sulfoxides as they form, and (ii) the α-alkoxy-substituted Grignard reagent is configurationally stable at room temperature for 30 min.
authors: Department of Chemistry, University of York, Heslington, York YO10 5DD, United Kingdom.
authors: Peter J
authors: PJ
authors: Rayner
authors: Peter
authors: P
authors: O'Brien
authors: Richard A J
authors: RA
authors: Horan
mesh_terms: D007202:Indicators and Reagents / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D007202:Indicators and Reagents