An Improved and Stereoselective Route to All-cis-2,6-Disubstituted 4-Hydroxypiperidines from Accessible 4-Substituted 4-N-Benzylaminobut-1-enes
作者:Alexey Varlamov、Vladimir Kouznetsov、Fedor Zubkov、Alexey Chernyshev、Olga Shurupova、Leonor Y. Vargas Méndez、Alirio Palma Rodríguez、Juliette Rivero Castro、Alfredo J. Rosas-Romero
DOI:10.1055/s-2002-25770
日期:——
The reaction between allylmagnesium bromide and imines 5a-l leads to the corresponding 4-substituted 4- N-benzy- laminobut-1-enes 6a-l, which were oxidized in a regioselective manner to the alkenylnitrones 7a-l. The intramolecular 1,3-dipolar cycloaddition of these nitrones gave 2-spiroannulated or 2-substi- tuted 6-exo-phenyl-1-aza-7-oxabicyclo(2.2.1)heptanes 8a-j. Re- ductive cleavage of the N-O
烯丙基溴化镁和亚胺 5a-1 之间的反应产生相应的 4-取代的 4-N-苄基氨基丁-1-烯 6a-1,其以区域选择性方式被氧化成烯基硝酮 7a-1。这些硝酮的分子内 1,3-偶极环加成得到 2-螺环化或 2-取代的 6-exo-phenyl-1-aza-7-oxabicyclo(2.2.1)庚烷 8a-j。所获得的自行车的 NO 键的还原裂解以良好的产率提供了多种取代的 4-羟基哌啶 9a-h。这种立体选择性方法允许制备全顺式-4-羟基-6-苯基-2-壬基哌啶(9i),一种与树蛙生物碱241D 的密切类似物。