Pybox/Lanthanide-Catalysed Diels–Alder Reactions with an Unsaturated α-Oxo Ester or 3-Alkenoyl-2-oxazolidinone as Dienophile: The Sense of Stereoinduction in Five- or Six-Membered Bidentate Reagent Coordination
作者:Giovanni Desimoni、Giuseppe Faita、Mariella Mella、Francesca Piccinini、Marco Toscanini
DOI:10.1002/ejoc.200600955
日期:2007.3
respectively, on the face-selectivity of the reaction. Only the ScIII triflate complex of 1 was found to be a very selective catalyst in the reaction with cinnamoyloxazolidinone 3, which allowed almost complete stereocontrol. The reaction between cyclopentadiene and methyl keto ester 4 was more complicated because, in addition to the expected normal DA adducts 7 and 8, the less expected endo-9 product
环戊二烯与 3-肉桂酰基-1,3-恶唑烷酮 (3) 和 (E)-2-氧代-4-苯基-3-丁烯酸甲酯 (4) 的对映选择性 Diels-Alder (DA) 反应在以下物质存在下进行(4'S,5'S)-2,6-双[4'-(三异丙基甲硅烷氧基甲基)-5'-苯基-1',3'-恶唑啉-2'-基]吡啶的镧系元素三氟甲磺酸盐络合物(1)具有进行了比较。这项工作的目的是比较α-和β-二羰基衍生物分别通过五元或六元环螯合与催化剂的阳离子位点配位对反应面选择性的影响。在与肉桂酰恶唑烷酮 3 的反应中,只有 ScIII 三氟甲磺酸盐络合物被发现是非常有选择性的催化剂,这使得几乎完全立体控制。环戊二烯和甲基酮酯 4 之间的反应更加复杂,因为,除了预期的正常 DA 加合物 7 和 8 外,还获得了 [4+2] 杂-DA (HDA) 反应的不太预期的内 9 产物,该反应是由 α-酮酯作为杂二烯产生的。[3,3] HDA