Isomerization and deuterium scrambling evidence for a change in the rate-limiting step during imine hydrogenation by Shvo's hydroxycyclopentadienyl ruthenium hydride

被引:104
作者
Casey, CP [1 ]
Johnson, JB [1 ]
机构
[1] Univ Wisconsin, Dept Chem, Madison, WI 53706 USA
关键词
D O I
10.1021/ja044450t
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
Hydroxycyclopentadienyl ruthenium hydride 5 efficiently reduces imines below room temperature. Better donor substituents on nitrogen give rise to faster rates and a shift of the rate-determining step from hydrogen transfer to amine coordination. Reduction of electron-deficient N-benzilidenepentafluoroaniline (8) at 11 degreesC resulted in free amine and kinetic isotope effects of k(OH)/k(OD) = 1.61 +/- 0.08, k(RuH) = 2.05 +/- 0.08, and k(RuHOH)/k(RuDOD) = 3.32 +/- 0.14, indicative of rate-limiting concerted hydrogen transfer, a mechanism analogous to that proposed for aldehyde and ketone reduction. Reduction of electron-rich N-alkyl-substituted imine, N-isopropyl-(4-methyl)benzilidene amine (9), was accompanied by facile imine isomerization and scrambling of deuterium labels from reduction with 5-RuDOH into the N-alkyl substituent of both the amine complex and into the recovered imine. Inverse equilibrium isotope effects were observed in the reduction of N-benzilidene-tert-butylamine (11) at -48 degreesC (k(OH)/k(OD) = 0.89 +/- 0.06, k(RUH)/k(RUD) = 0.64 +/- 0.05, and k(RuHOH)/k(RuDOD) = 0.56 +/- 0.05). These results are consistent with a mechanism involving reversible hydrogen transfer followed by rate-limiting amine coordination.
引用
收藏
页码:1883 / 1894
页数:12
相关论文
共 22 条
[1]   Mechanism of the hydrogenation of ketones catalyzed by trans-dihydrido(diamine)ruthenium(II) complexes [J].
Abdur-Rashid, K ;
Clapham, SE ;
Hadzovic, A ;
Harvey, JN ;
Lough, AJ ;
Morris, RH .
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 2002, 124 (50) :15104-15118
[2]   RuHCl(diphosphine)(diamine): Catalyst precursors for the stereoselective hydrogenation of ketones and imines [J].
Abdur-Rashid, K ;
Lough, AJ ;
Morris, RH .
ORGANOMETALLICS, 2001, 20 (06) :1047-1049
[3]   Catalytic cycle for the asymmetric hydrogenation of prochiral ketones to chiral alcohols:: Direct hydride and proton transfer from chiral catalysts trans-Ru(H)2(diphosphine)(diamine) to ketones and direct addition of dihydrogen to the resulting hydridoamido complexes [J].
Abdur-Rashid, K ;
Faatz, M ;
Lough, AJ ;
Morris, RH .
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 2001, 123 (30) :7473-7474
[4]   (CYCLOPENTADIENONE)RUTHENIUM CARBONYL-COMPLEXES - A NEW CLASS OF HOMOGENEOUS HYDROGENATION CATALYSTS [J].
BLUM, Y ;
CZARKIE, D ;
RAHAMIM, Y ;
SHVO, Y .
ORGANOMETALLICS, 1985, 4 (08) :1459-1461
[5]   ACTIVATION ENTHALPY AND ENTROPY FOR INVERSION-ROTATION PROCESS IN DIBENZYLMETHYLAMINE [J].
BUSHWELLER, CH ;
BILOFSKY, HS ;
ONEIL, JW .
TETRAHEDRON, 1972, 28 (10) :2697-+
[6]   Kinetic isotope effect evidence for a concerted hydrogen transfer mechanism in transfer Hydrogenations catalyzed by [p-(Me2CH)C6H4Me]Ru-(NHCHPhCHPhNSO2C6H4-p-CH3) [J].
Casey, CP ;
Johnson, JB .
JOURNAL OF ORGANIC CHEMISTRY, 2003, 68 (05) :1998-2001
[7]   Hydrogen transfer to carbonyls and imines from a hydroxycyclopentadienyl ruthenium hydride: Evidence for concerted hydride and proton transfer [J].
Casey, CP ;
Singer, SW ;
Powell, DR ;
Hayashi, RK ;
Kavana, M .
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 2001, 123 (06) :1090-1100
[8]  
CASEY CP, UNPUB
[9]   Hydrogenation of aromatic ketones catalyzed by (η5-C5(CH3)5)Ru complexes bearing primary amines [J].
Ito, M ;
Hirakawa, M ;
Murata, K ;
Ikariya, T .
ORGANOMETALLICS, 2001, 20 (03) :379-381
[10]   A chiral rhodium complex for rapid asymmetric transfer hydrogenation of imines with high enantioselectivity [J].
Mao, JM ;
Baker, DC .
ORGANIC LETTERS, 1999, 1 (06) :841-843