Syn-SN2' pathway in the reaction of certain .gamma.-(mesyloxy) .alpha.,.beta.-enoates with RCu(CN)MgX.BF3 reagents. Importance of MgX and bulky R group upon the diastereoselectivity
摘要:
The reactions of protected serine- and threonine-derived gamma-(mesyloxy) alpha,beta-unsaturated esters with various magnesio organocyanocopper Lewis acid complexes have been investigated. The formation of syn-S(N)2' products, in addition to the normally expected anti-S(N)2' products, is taken as an indication that the reaction proceeds by a mechanism involving coordination of the magnesiocuprate with the C(delta)-N:C(gamma)-O syn-gamma-(mesyloxy) alpha,beta-enoates.
Highly Stereoselective Intramolecular S<sub>N</sub>2′ Cyclization Yielding Chiral Oxazolidin-2-ones: General Route to α-Hydroxy-β-amino Acids
作者:Ki Hun Park、Woo Duck Seo、Marcus J. Curtis-Long、Jin Hyo Kim、Jong Keun Park、Ki Min Park
DOI:10.1055/s-2005-872264
日期:——
Intramolecular nucleophilic attack onto allylsulfonates promoted by silica gel acting as an acid catalyst provides expedient stereoselective access to 4,5-difunctionalized oxazolidin-2-ones. Precursors were prepared efficiently from enantiopure α-amino acids and subsequent manipulation of the oxazolidin-2-ones yielded enantiopure α-hydroxy-β-amino acids.
Pd-catalyzed ScN' reactions: Stereoselective formation of cyclic carbamates from tert-butyldimethylsilyl carbamates
作者:Glen W. Spears、Koji Nakanishi、Yasufumi Ohfune
DOI:10.1016/s0040-4039(00)98065-1
日期:1990.1
Stereoselective formation of cyclic carbamates was achieved by the intramolecular trapping of a tert-butyldimethylsilyloxycarbonyl group with allylic esters upon activation with fluoride and cat. Pd(O). The reactive conformation is proposed to be D. The highly stereo;elective reaction of 2° allylic esters allowed a detailed reaction mechanism to be proposed which accounts for the observed selectivities