19 (37) aReactions were performed under an atmosphere of dry argon under the following conditions:(a)-78 OC to rt (18 h);(b) 0 OC to rt (18 h);(c)-78" C to rt, followed by reflux for 18 h.* Isolated yield after crystallization or flash chromatography. 12 in good yield (Table I). Deprotonation of 6 is rather slow at-78 OC due to the bulky disilazane. If insufficient time is allowed for deprotonation of 6 (< 40 min) prior to addition of the imino phosphate, variable ...
