The reaction of crotyltrialkylstannanes (1) with aldehydes in the presence of BF3,OEt2, produces the corresponding erythro homoallyl alcohols (2) predominantly regardless of the geometry of the double bond. Further, the Lewis acid mediated reaction exhibits the enhanced Cram selectivity in comparison with other allylic organometallic reactions which proceed in the absence of Lewis acids. Use of AlCl3-i-PrOH
The reaction of but-2-enyltributylstannane with certain aldehydes in the presence of AlCl3–PriOH produces the α-adduct (3) either predominantly or exclusively, while the reaction in the presence of ordinary Lewis acids, such as TiCl4, SnCl4, and BF3·OEt2, affords the γ-adduct (2) exclusively.
A new, highly stereoselective approach to pyrrolidines via overall 5-endo-trig cyclisations of homoallylic tosylamides
作者:Andrew D. Jones、David W. Knight
DOI:10.1039/cc9960000915
日期:——
Iodocyclisations of E-homoallylic tosylamides 7 lead to excellent yields of either 2,5-trans-or 2,5-cis-3-iodopyrrolidines (10 or 11), depending upon the reaction conditions.