Carbon-fluorine bond activation coupled with carbon-hydrogen bond formation α to iridium:: Kinetics, mechanism, and diastereoselectivity

被引:38
作者
Garratt, SA [1 ]
Hughes, RP [1 ]
Kovacik, I [1 ]
Ward, AJ [1 ]
Willemsen, S [1 ]
Zhang, DH [1 ]
机构
[1] Dartmouth Coll, Dept Chem, Hanover, NH 03755 USA
关键词
D O I
10.1021/ja0545012
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
Reactions of iridium(fluoroalkyl)hydride complexes Cp*Ir(PMe3)(CF2RF)Y (R-F = F, CF3; Y = H, D) with LutHX (Lut = 2,6-dimethylpyridine; X = Cl, l) results in C-F activation coupled with hydride migration to give Cp*Ir(PMe3)(CYFRF)X as variable mixtures of diastereomers. Solution conformations and relative diastereomer configurations of the products have been determined by F-19{H-1}HOESY NMR to be (Sc, S-Ir)(R-C, R-Ir) for the kinetic diastereomer and (R-C, S-Ir)(S-C, R-Ir) for its thermodynamic counterpart. Isotope labeling experiments using LutDCl/Cp*Ir(PMe3)(CF2RF)H and Cp*Ir(PMe3)(CF2RF)D/LutHCl) showed that, unlike a previously studied system, H/D exchange is faster than protonation of the alpha-CF bond, giving an identical mixture of product isotopologues from both reaction mixtures. The kinetic rate law shows a first-order dependence on the concentration of iridium substrate, but a half-order dependence on that of LutHCl; this is interpreted to mean that LutHCl dissociates to give HCl as the active protic source for C-F bond activation. Detailed kinetic studies are reported, which demonstrate that lack of complete diastereoselectivity is not a function of the C-F bond activation/H migration steps but that a cationic intermediate plays a double role in loss of diastereoselectivity; the intermediate can undergo epimerization at iridium before being trapped by halide and can also catalyze the epimerization of kinetic diastereomer product to thermodynamic product. A detailed mechanism is proposed and simulations performed to fit the kinetic data.
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页码:15585 / 15594
页数:10
相关论文
共 93 条
[1]   CATALYTIC ACTIVATION OF CARBON-FLUORINE BONDS BY A SOLUBLE TRANSITION-METAL COMPLEX [J].
AIZENBERG, M ;
MILSTEIN, D .
SCIENCE, 1994, 265 (5170) :359-361
[2]   DISPLACEMENT OF NORBORNADIENE (NBD) FROM PT(CF3)2(NBD) BY WEAK DONOR LIGANDS-L, AND REACTIONS OF CIS-PT(CF3)2L2 WITH WATER AND ACIDS [J].
APPLETON, TG ;
BERRY, RD ;
HALL, JR ;
NEALE, DW .
JOURNAL OF ORGANOMETALLIC CHEMISTRY, 1989, 364 (1-2) :249-273
[3]   UNUSUALLY MILD AND SELECTIVE HYDROCARBON C-H BOND ACTIVATION WITH POSITIVELY CHARGED IRIDIUM(III) COMPLEXES [J].
ARNDTSEN, BA ;
BERGMAN, RG .
SCIENCE, 1995, 270 (5244) :1970-1973
[4]   ETA(2)-COORDINATION AND C-F ACTIVATION OF HEXAFLUOROBENZENE BY CYCLOPENTADIENYLRHODIUM AND CYCLOPENTADIENYLIRIDIUM COMPLEXES [J].
BELT, ST ;
HELLIWELL, M ;
JONES, WD ;
PARTRIDGE, MG ;
PERUTZ, RN .
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 1993, 115 (04) :1429-1440
[5]   Routes to fluorinated organic derivatives by nickel mediated C-F activation of heteroaromatics [J].
Braun, T ;
Perutz, RN .
CHEMICAL COMMUNICATIONS, 2002, (23) :2749-2757
[6]  
Braun T, 2002, ANGEW CHEM INT EDIT, V41, P2745, DOI 10.1002/1521-3773(20020802)41:15<2745::AID-ANIE2745>3.0.CO
[7]  
2-C
[8]   Catalytic C-F activation of polyfluorinated pyridines by nickel-mediated cross-coupling reactions [J].
Braun, T ;
Perutz, RN ;
Sladek, MI .
CHEMICAL COMMUNICATIONS, 2001, (21) :2254-2255
[9]   Coordination and oxidative addition of octafluoronaphthalene at a nickel centre: isolation of an intermediate in C-F bond activation [J].
Braun, T ;
Cronin, L ;
Higgitt, CL ;
McGrady, JE ;
Perutz, RN ;
Reinhold, M .
NEW JOURNAL OF CHEMISTRY, 2001, 25 (01) :19-21
[10]  
Braun T, 1999, ANGEW CHEM INT EDIT, V38, P3326, DOI 10.1002/(SICI)1521-3773(19991115)38:22<3326::AID-ANIE3326>3.0.CO