JV-Boc-pyrrolidines

Summary Our research on a-metalated organosilanes currently focuses on (aminomethyl)silanes containii a defined stereogenic center next to the silicon center. A synthetic route based on the preparation of 2-silyl-substituted pyrrolidines was developed. The racemic product could be synthesized by metalation of JV-Boc-pyrrolidine in the presence of TMEDA and conversion with the corresponding chlorosilane, whereas the enantioenriched form was achieved by metalation in the presence of the chiral amine (-)-sparteine. Subsequent metalation and transformation reactions yielded the formation of the corresponding (aminomethyl)(lithiomethyl)silane. 

The asymmetric deprotonation of JV-Boc-pyrrolidine (1) was performed by using i-BuLi/(-)-sparteine, resulting in the formation of the corresponding enantioenriched lithiumorganyle. After reaction of this lithium compound with chloromethyldiphenylsilane, the enantioenriched compound (5)-2-(methyldiphenylsilyl)-lV-Boc-pyiTolidine [(5)-2 (e. r. = 94 6), Scheme 2] was isolated in 88% yield. The use of TMEDA instead of (-)-sparteine afforded rac-1 (70% yield). 

For calculations on the (-)-sparteine-mediated JV-Boc-pyrrolidines, see Wiberg KB, Bailey WF (2000) Angew Chem 112 2211 Angew Chem Int Ed 39 2127... 

Scheme 11.28 a-Arylation of JV-Boc-pyrrolidine using catal Tic CuCN and palladium. 

---