螺[4,4]-1,6-壬二烯骨架手性双膦配体的合成

Synthesis of chiral diphosphine ligand with a spiro[4,4]-1,6-nonadiene skeleton

从方便易得的原料出发,以钯催化的烯基三氟甲磺酸酯与二苯基膦氧化物的偶联反应为关键步骤,合成了螺[4,4]-1,6-壬二烯骨架的手性双膦配体1.其中,关键中间体5的拆分是通过半制备手性液相色谱实现的,并通过该化合物的X射线单晶衍射分析确定了其中螺碳原子的绝对构型.配体(S)-1的Rh(I)络合物在α-乙酰氨基肉桂酸的氢化中表现出中等的对映选择性(53%ee).配体(S)-1的Cu(I)络合物能以较好的反应活性实现苯乙酮的不对称氢化,产物的对映体过量可以达到67%.

The new chiral diphosphine ligand 1,bearing a spiro[4,4]-1,6-nonadiene in its backbone,was readily synthesized from the enol triflate ester of spiro-[4,4]-1,6-nonadione with Pd-catalyzed coupling reactions as the key steps.Both optical enantiomers of key precursor 5 were obtained by semi-preparative HPLC on a chiral column and the absolute configuration of the spiro center in this intermediate was deduced from an X-ray diffraction analysis.Ligand 1 was tested in the Rh（I）-catalyzed asymmetric hydrogenation of α-dehydroamido acid,giving the product in 53% ee.Ligand 1 was also evaluated in Cu（I）-catalyzed asymmetric hydrogenation of acetophenone,and good reactivity and promising enantioselectivity were observed（67% ee） in this case.