以(R)或(S)-H8-BINOL为配体骨架,合成具有螺旋结构C3对称的六个新型单齿亚磷酸酯配体,并将它们首次成功应用于Rh(acac)(CO)2催化苯乙烯的不对称氢甲酰化,和Cu(OTf)2催化二乙基锌对链烯酮的不对称1,4-共轭加成反应研究中.在铑催化苯乙烯的不对称氢甲酰化反应中,螺旋结构C3对称的单齿亚磷酸酯配体给出高的催化活性(转化率93%)和支链醛/直链醛区域选择性(b/n=95/5),和较低的对映选择性[28% ee (R)].在铜催化二乙基锌对链烯酮的不对称1,4-共轭加成反应中,以查尔酮为底物筛选配体,优化反应条件;在优化的反应条件下,考察11种不同结构链状烯酮底物对反应的适应性;以Cu(OTf)2作为催化剂前体,乙醚为溶剂,在-20℃,配体(R)-3中大位阻金刚烷基和(R)-H8-联萘基团之间的空间结构匹配是获得98%分离产率和72%(R)对映选择性的关键因素,产物绝对构型主要由配体结构中H8-联萘基团的构型决定.研究结果证明C3对称的新型单齿亚磷酸酯配体在不对称氢甲酰化和1,4-共轭加成反应中具有应用潜力.
A family of the novel chiral helical C3-symmetric monophosphite ligands has been synthesized from axially chiral (R)-or (S)-H8-BINOL and PCl3. The performance of these ligands in asymmetric catalysis was evaluated by the Rh-catalyzed asymmetric hydroformylation of styrene, and the Cu-catalyzed asymmetric 1,4-conjugate addition of diethylzinc to acyclic enones. The catalytic hydroformylation of styrene gave rather high conversion (93%), high regioselectivity (b/n=95/5) and low enantioselectivity[28% ee (R)] using ligand (R)-2 in tetrahydrofuran at room temperature. Under the optimal 1,4-conjugate addition of ZnEt2 to chalcone 3a conditions, eleven acyclic enones 4a-4k were all converted smoothly to the 1,4-adducts with high enantiomeric excess. Using Cu(OTf)2 as catalyst precursor and Et2O as solvent at -20℃, the structure of ligand (R)-3 comprising a partially hydrogenated 2,2'-(1,1'-binaphthyl)-phosphite scaffold and an adamantyl moiety was key factor in improving catalytic activity and the enantioselectivity with up to 98% yield and 72% ee (R). The sense of enantiodiscrimination of the reaction was controlled by the configuration of the diaryl phosphite moieties.