Catalytic intramolecular hydroamination of aminoallenes using titanium complexes of chiral, tridentate, dianionic imine-diol ligands
Catalytic intramolecular hydroamination of aminoallenes using titanium complexes of chiral, tridentate, dianionic imine-diol ligands
复制标题
使用手性、三齿、双阴离子亚胺-二醇配体的钛配合物催化氨基丙二烯的分子内氢胺化
DOI：
10.1039/c8dt05156a
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发表时间：
2019
影响因子：
4
通讯作者：
Johnson, Adam R.
中科院分区：
文献类型：
--
作者：
Sha, Fanrui;Mitchell, Benjamin S.;Ye, Christopher Z.;Abelson, Chase S.;Reinheimer, Eric W.;LeMagueres, Pierre;Ferrara, Joseph D.;Takase, Michael K.;Johnson, Adam R.
使用甲基或苯基格氏试剂进行D-或L-苯丙氨酸或缬氨酸烷基酯的烷基化。随后与水杨醛、3，5-二叔丁基水杨醛或5-氟水杨醛缩合形成三齿X2 L型席夫碱配体。手性位移NMR证实了在合成期间立体化学的保留。四个配体的X射线晶体结构显示分子间或分子内氢键相互作用。配体通过质子分解和置换两当量的HNMe 2与钛试剂Ti（NMe 2）4或TiCl（NMe 2）3配位。测定了Ti（X2 L）Cl（NMe 2）的晶体结构，该配合物具有扭曲的四方锥几何结构，轴向配体为NMe 2。双-二甲基酰胺配合物是二-和三取代氨基联烯的闭环氢胺化的活性催化剂。七-4，5-二烯基胺在135 °C下与5摩尔%催化剂反应，得到6-乙基-2，3，4，5-四氢吡啶（40-72%）以及Z-和E-2-丙烯基-吡咯烷（25-52%）的混合物。6-甲基-庚-4，5-二烯基胺在135 °C下与5摩尔%催化剂的闭环反应仅产生2-（2-甲基-丙烯基）-吡咯烷。得到的吡咯烷产物的对映体过量高达17%。
Alkylation of D- or L-phenylalanine or valine alkyl esters was carried out using methyl or phenyl Grignard reagents. Subsequent condensation with salicylaldehyde, 3,5-di-tert-butylsalicylaldehyde, or 5-fluorosalicylaldehyde formed tridentate, X2L type, Schiff base ligands. Chiral shift NMR confirmed retention of stereochemistry during synthesis. X-ray crystal structures of four of the ligands show either inter- or intramolecular hydrogen bonding interactions. The ligands coordinate to the titanium reagents Ti(NMe2)4 or TiCl(NMe2)3 by protonolysis and displacement of two equivalents of HNMe2. The crystal structure of one example of Ti(X2L)Cl(NMe2) was determined and the complex has a distorted square pyramidal geometry with an axial NMe2 ligand. The bis-dimethylamide complexes are active catalysts for the ring closing hydroamination of di- and trisubstituted aminoallenes. The reaction of hepta-4,5-dienylamine at 135 °C with 5 mol% catalyst gives a mixture of 6-ethyl-2,3,4,5-tetrahydropyridine (40–72%) and both Z- and E-2-propenyl-pyrrolidine (25–52%). The ring closing reaction of 6-methyl-hepta-4,5-dienylamine at 135 °C with 5 mol% catalyst gives exclusively 2-(2-methyl-propenyl)-pyrrolidine. The pyrrolidine products are obtained with enantiomeric excesses up to 17%.