In Search ofexo-Selective Catalysts for Enantioselective 1,3-Dipolar Cycloaddition between Acryloyloxazolidinone and Diphenylnitrone
作者:Giovanni Desimoni、Giuseppe Faita、Mariella Mella、Massimo Boiocchi
DOI:10.1002/ejoc.200400605
日期:2005.3
observed with the catalysts derived from this ligand and CoII or ZnII, which gave good levels of exo enantioselectivity, with 84% ee of (3′S,4′S)-4. When 8c was used as ligand, MgII, CoII and NiII give exo-selective catalysts, and the enantiomer (3′R,4′R)-4 was obtained with good dr and excellent ee. The unknown absolute configuration of the exo enantiomers 4 was established by structure correlation with
丙烯酰恶唑啉酮 1 和二苯基硝酮 2 之间的 1,3-偶极环加成 (1,3-DC) 由三 (4R)-苯基双(恶唑啉) [框 = 双(恶唑啉)] - 5-未取代 (8a) 的配合物催化,或 4,5-顺-和-反-二苯基取代的 (8b, 8c) - 用几种二价阳离子的高氯酸盐。使用 MgII- 和 NiII-8a 催化剂获得正常的内选择性,内对映异构体 (3'R,4'S)- 或 (3'S,4'R)-3 的形成取决于 4- A 分子筛 (MS)。使用衍生自该配体和 CoII 或 ZnII 的催化剂观察到不同的结果,其具有良好的外对映选择性水平,(3'S,4'S)-4 的 ee 为 84%。当以8c为配体时,MgII、CoII和NiII提供外选择性催化剂,得到对映体(3'R,4'R)-4,具有良好的dr和优异的ee。外向对映异构体 4 的未知绝对构型是通过与从 2 和 (S)-3-丙烯酰基-4-苄基-2-恶唑烷酮