Diastereoselective ortho-Metalation of a Chiral Ferrocenylphosphonic Diamide and Its Organotin Derivatives
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The syntheses of the enantiopure ferrocenylphosphonic diamide (3aR,7aR)-2-ferrocenyl-3a,4,5,6,7,7a-octahydro-1,3-dimethyl-1,3,2-benzodiazaphosphole 2-oxide ((R,R)-FcP(O)(DMCDA), (R,R)-1) and its enantiomer (S,S)-FcP(O)(DMCDA) ((S,S)-1) are reported. Their ortho lithiation and subsequent treatment with Ph3SnCl selectively provided the corresponding tetraorganotin derivatives FcP(O)(DMCDA)SnPh3 ((R,R,RP)-2 and (S,S,SP)-2) in a diastereoselective ratio of 88:12. The absolute configuration of the major diastereomer was confirmed by single-crystal X-ray diffraction analysis. DFT calculations revealed that kinetic effects of the lithiation step cause the high diastereoselectivity of the formation of (R,R,RP)-2. Further functionalization of (R,R,RP)-2 with elemental iodine gave the enantiopure organotin iodide derivatives FcP(O)(DMCDA)SnInPh3–n ((R,R,RP)-3:, n = 1; (R,R,RP)-4, n = 2, (R,R,RP)-5, n = 3). The triorganotin fluoride FcP(O)(DMCDA)SnFPh2 ((R,R,RP)-6) was obtained by the reaction of (R,R,RP)-3 in dichloromethane with aqueous KF solution. The reaction of the compound (R,R,RP)-3 with silver triflate gave the R,R,RP-configurated triorganotin triflate FcP(O)(DMCDA)SnPh2(OTf) (7), which exists as a contact ion pair in the solid state and shows dynamic behavior in solution. The reaction of 7 with Ph3PO afforded the corresponding organotin salt [FcP(O)(DMCDA)SnPh2(OPPh3)][OTf] ((R,R,RP)-8).
本文报道了对映纯二茂铁基膦酰胺(3aR,7aR)-2-二茂铁基-3a,4,5,6,7,7a-八氢-1,3-二甲基-1,3,2-苯二氮杂膦烷2-氧化物((R,R)-FcP(O)(DMCDA)，(R,R)-1)及其对映体(S,S)-FcP(O)(DMCDA)（(S,S)-1）的合成方法。对该化合物进行邻位锂化，随后与三苯基氯化锡（Ph3SnCl）反应，可选择性得到对应四有机锡衍生物FcP(O)(DMCDA)SnPh3（(R,R,RP)-2与(S,S,SP)-2），二者的非对映选择性比例为88:12。通过单晶X射线衍射分析，确认了主要非对映异构体的绝对构型。密度泛函理论（DFT）计算表明，锂化步骤的动力学效应是导致(R,R,RP)-2生成具有高非对映选择性的原因。对(R,R,RP)-2进行进一步官能化，与单质碘反应可得到对映纯有机锡碘化物衍生物FcP(O)(DMCDA)SnInPh3–n（(R,R,RP)-3：n=1；(R,R,RP)-4：n=2；(R,R,RP)-5：n=3）。将(R,R,RP)-3在二氯甲烷中与氟化钾水溶液反应，得到三有机锡氟化物FcP(O)(DMCDA)SnFPh2（(R,R,RP)-6）。化合物(R,R,RP)-3与三氟甲磺酸银反应，得到具有R,R,RP构型的三有机锡三氟甲磺酸盐FcP(O)(DMCDA)SnPh2(OTf)（7），该化合物在固态下以接触离子对形式存在，且在溶液中表现出动态行为。7与三苯基氧膦（Ph3PO）反应，得到相应的有机锡盐[FcP(O)(DMCDA)SnPh2(OPPh3)][OTf]（(R,R,RP)-8）。
