Reuber Jenny, Fröhlich Roland, Hoppe Dieter
Organisch-Chemisches Institut, Westfälische Wilhelms-Universität Münster, Corrensstrasse 40, 48149 Münster, Germany.
Org Lett. 2004 Mar 4;6(5):783-6. doi: 10.1021/ol0364677.
1-trimethylsilyl-1-alkenyl carbamates 1 are deprotonated by n-butyllithium/(-)-sparteine (2) with a high degree of enantiotopic differentiation in the gamma-position to form the enantiomerically enriched allyllithium derivatives 3. Trapping these with several electrophiles proceeds stereospecifically in an anti-S(E)' or syn-S(E)' substitution to form products 4 or ent-4, respectively. Compounds 3a (R = Me) and 3b (R = Ph) exhibit toward carbonyl electrophiles opposite senses of almost complete stereospecificity, thus for 3b.2 the involvement of a eta(3)-complex is suggested. [reaction: see text]
