NCN pincer palladium complexes: their preparation via a ligand introduction route and their catalytic properties.
NCN pincer palladium complexes: their preparation via a ligand introduction route and their catalytic properties.
复制标题
DOI：
10.1021/ja052780n
复制
发表时间：
2005-08
影响因子：
15
通讯作者：
K. Takenaka;Maki Minakawa;Y. Uozumi
中科院分区：
文献类型：
--
作者：
K. Takenaka;Maki Minakawa;Y. Uozumi
广泛的NCN钳形钯配合物，[4-叔丁基-2，6-二（N-烷基亚氨基）苯基]氯钯（烷基=正丁基、苄基、环己基、叔丁基、金刚烷基、苯基、4-甲氧基苯基），容易地由反式-（4-叔丁基-2，6-二甲酰基苯基）氯双通过脱水引入相应的烷基亚氨基配体基团的（三苯基膦）钯（配体引入途径）以优异的产率（71-98%）进行。NMR研究表明，[4-叔丁基-2，6-双（N-烷基亚氨基）苯基]氯代双（三苯基膦）钯通过分子内亚氨基和三苯基膦配体的配位/解离与相应的NCN钳形配合物处于平衡状态。以该前体为原料，通过与脯氨酸酰苯胺缩合反应，高产率地合成了一系列以吡咯并咪唑酮为反式螯合给体的手性NCN钳形配合物[4-叔丁基-2，6-双{（3R，7aS）-2-苯基六氢-1H-吡咯并[1，2-c]咪唑-1-酮-3-基}苯基]氯化钯。研究了NCN亚胺和NCN吡咯并咪唑酮钳形钯配合物在Heck反应和不对称Michael反应中的催化性能，证明了它们的高催化活性和高对映选择性.
A wide range of NCN pincer palladium complexes, [4-tert-butyl-2,6-bis(N-alkylimino)phenyl]chloropalladium (alkyl = n-butyl, benzyl, cyclohexyl, tert-butyl, adamantyl, phenyl, 4-methoxyphenyl), were readily prepared from trans-(4-tert-butyl-2,6-diformylphenyl)chlorobis(triphenylphosphine)palladium via dehydrative introduction of the corresponding alkylimino ligand groups (ligand introduction route) in excellent yields (71-98%). NMR studies on this route for forming pincer complexes revealed the intermediacy of [4-tert-butyl-2,6-bis(N-alkylimino)phenyl]chlorobis(triphenylphosphine)palladium which is in equilibrium with the corresponding NCN pincer complexes via coordination/dissociation of the intramolecular imino groups and triphenylphosphine ligands. A series of chiral NCN pincer complexes bearing pyrroloimidazolone units as the trans-chelating donor groups, [4-tert-butyl-2,6-bis{(3R,7aS)-2-phenylhexahydro-1H-pyrrolo[1,2-c]imidazol-1-on-3-yl}phenyl]chloropalladium, were also prepared from the same precursor via condensation with proline anilides in high yields. The catalytic properties of the NCN imino and the NCN pyrroloimidazolone pincer palladium complexes were examined in the Heck reaction and the asymmetric Michael reaction to demonstrate their high catalytic activity and high enantioselectivity.