On the Origin of Asymmetric Induction of the Palladium-Catalyzed Allylic Substitution Reaction with Chiral 4,4-Disubstituted 4,5-Dihydro-2-(phosphinoaryl)oxazole Ligands
作者:Silvia Schaffner、Jürgen F. K. Müller、Markus Neuburger、Margareta Zehnder
DOI:10.1002/hlca.19980810533
日期:——
4-monosubstituted 4,5-dihydro-2-(phosphinoaryl)oxazole ligand 1a reveals important structural differences (Fig. 3). 1H-NMR Spectroscopic investigation confirm that the 4,4-disubstituted 4,5-dihydro-2-(phosphinoaryl)oxazole ligand 4 of 5 and 6 shows the same conformation in solution as in the solid state (Table 2). The application of ligand (S)-4 in the Pd-catalyzed allylic substitution demonstrates a
的X射线分析(η 3 -烯丙基)4-苄基-2- [2-(二苯基膦基κP)苯基] -4,5-二氢- 4-4-甲基恶唑κ Ñ }合钯(II)六氟磷酸盐(5)与类似的[将Pd(η 3 -1,3- diphenylallyl)]络合物6呈现。与(ηA比较3 -烯丙基) -和(η-1,3- diphenylallyl)钯络合物2和3分别含有,4-单取代的4,5-二氢-2-(phosphinoaryl)恶唑配体1a中揭示了重要结构差异(图3)。1个H-NMR光谱学研究证实,4,4-二取代4,5-二氢-2-(phosphinoaryl)恶唑配体4的5只6示出了在溶液中的相同的构象在固体状态(表2)。配体(S)-4在Pd催化的烯丙基取代中的应用表明,中间体(参见络合物6)中烯丙基配体的取向与烯丙基取代产物的绝对构型之间存在构型关系(表3) 。