Increased catalytic activity of primary amine palladacycles in biomimetic hydrolysis of N-t-BOC-S-methionine p-nitrophenyl ester
作者:Sergey A Kurzeev、Gregory M Kazankov、Alexander D Ryabov
DOI:10.1016/s0020-1693(00)00101-8
日期:2000.7
The kinetics of hydrolysis of N-t-BOC-S-methionine p-nitrophenyl ester (5) promoted by the cyclopalladated complexes of tertiary and primary benzylamines [Pd(C6H4CHR%NR2)Cl(py)], where R Me (1 )a nd H( 3), R% H( a), S-Me (b) and R-Me (b), has been studied. In buffered solutions complexes 1 and 3 undergo aquation of the chloro ligand to afford species 2 and 4, respectively, and these carry out the hydrolysis
叔和伯苄胺[Pd(C6H4CHR%NR2)Cl(py)]的环钯配合物促进Nt-BOC-S-蛋氨酸对硝基苯酯(5)的水解动力学,其中R Me(1)和H(3),R%H(a),S-Me(b)和R-Me(b)已被研究。在缓冲溶液中,配合物1和3分别进行氯配体的水合反应,得到物种2和4,它们根据pH 8和25°C下的速率表达kobs ko kcat [Pd(II)] t进行水解。络合物2a-c,4a-c的kcat途径的速率常数分别等于2.5、2.1、2.2、32、220和260 M 1 s 1,表明苄胺(4a)和α-甲基苄胺(4b,c )配合物分别比N,N-二甲基苄胺配合物2a催化活性高大约十倍和一百倍。当活化的酯具有能够与Pd(II)结合的供体中心时,观察到这种剧烈的区分。与此相一致的是,所有研究的络合物在乙酸2,4-二硝基苯酯的水解中均显示出相似的活性(kcat:0.8 M 1 s 1)。推测在
Resolution of Secondary Phosphanes Chiral at Phosphorus by Means of Palladium Metallacycles