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Title: Experimental and Computational Studies on the Mechanism ofN-Heterocycle C-H Activation by Rh(I)

Abstract

No abstract prepared.

Authors:
; ; ;
Publication Date:
Research Org.:
Ernest Orlando Lawrence Berkeley NationalLaboratory, Berkeley, CA (US)
Sponsoring Org.:
USDOE Director. Office of Science. Basic EnergySciences
OSTI Identifier:
922718
Report Number(s):
LBNL-62058
Journal ID: ISSN 0002-7863; JACSAT; R&D Project: 402101; BnR: KC0302010; TRN: US200803%%450
DOE Contract Number:
DE-AC02-05CH11231
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of the American Chemical Society; Journal Volume: 128; Related Information: Journal Publication Date: 01/25/2006
Country of Publication:
United States
Language:
English
Subject:
37; RHODIUM; CATALYTIC EFFECTS; HETEROCYCLIC COMPOUNDS; CHEMICAL ACTIVATION; CHEMICAL REACTION KINETICS

Citation Formats

Wiedemann, Sean H, Lewis, Jared C., Ellman, Jonathan A., and Bergman,Robert G. Experimental and Computational Studies on the Mechanism ofN-Heterocycle C-H Activation by Rh(I). United States: N. p., 2006. Web. doi:10.1021/ja0576684.
Wiedemann, Sean H, Lewis, Jared C., Ellman, Jonathan A., & Bergman,Robert G. Experimental and Computational Studies on the Mechanism ofN-Heterocycle C-H Activation by Rh(I). United States. doi:10.1021/ja0576684.
Wiedemann, Sean H, Lewis, Jared C., Ellman, Jonathan A., and Bergman,Robert G. Wed . "Experimental and Computational Studies on the Mechanism ofN-Heterocycle C-H Activation by Rh(I)". United States. doi:10.1021/ja0576684.
@article{osti_922718,
title = {Experimental and Computational Studies on the Mechanism ofN-Heterocycle C-H Activation by Rh(I)},
author = {Wiedemann, Sean H and Lewis, Jared C. and Ellman, Jonathan A. and Bergman,Robert G.},
abstractNote = {No abstract prepared.},
doi = {10.1021/ja0576684},
journal = {Journal of the American Chemical Society},
number = ,
volume = 128,
place = {United States},
year = {Wed Dec 27 00:00:00 EST 2006},
month = {Wed Dec 27 00:00:00 EST 2006}
}
  • Cited by 19
  • The reaction of (C{sub 5}Me{sub 5}RhMe{sub 2}(Me{sub 2}SO)) with 2-, 3-, and 4-pyridinecarboxyaldehyde gave the appropriately substituted (C{sub 5}Me{sub 5}Rh(Me)(CO)(x-C{sub 5}H{sub 4}N)) (2, x = 2-4) in 80-90% yields; (C{sub 5}Me{sub 5}Ir(Me)(CO)(4-C{sub 5}H{sub 4}N)) was prepared analogously. The 2- and 3-pyridyl complexes were readily quaternized by reaction with MeI to give (C{sub 5}Me{sub 5}Rh(Me)(CO)(x-C{sub 5}H{sub 4}NMe))I, (x = 2, 3), but the (4-pyridyl)rhodium complex underwent coupling to give 1,4-dimethylpyridinium iodide and (C{sub 5}Me{sub 5}Rh(CO)Me(I)). The products from the last reaction with CD{sub 3}I were (C{sub 5}Me{sub 5}Rh(CO)Cd{sub 3}(I)) and (4-CH{sub 3}C{sub 5}H{sub 4}NCD{sub 3}{sup +}){sup {minus}}. On reaction of (C{submore » 5}Me{sub 5}Rh(Me)(CO)(4-C{sub 5}H{sub 4}N)) with other electrophiles (H{sup +}BF{sub 4}{sup {minus}}, Et{sub 3}O{sup +}BF{sub 4}{sup {minus}}), evidence for the formation of unstable salts, (C{sub 5}Me{sub 5}Rh(Me)(CO)(4-C{sub 5}H{sub 4}NH)){sup +} and (C{sub 5}Me{sub 5}Rh(Me)(CO)(4-C{sub 5}H{sub 4}NEt)){sup +}, was obtained. In contrast, the complex (C{sub 5}Me{sub 5}Rh(Me)(CO)(4-C{sub 5}H{sub 4}N)) reacted with methyl iodide to give the stable (C{sub 5}Me{sub 5}Ir(Me)(CO)(4-C{sub 5}H{sub 4}NMe)){sup +}I{sup {minus}}. (C{sub 5}Me{sub 5}Rh(Me)(CO)(x-C{sub 5}H{sub 4}N)) (x = 3, 4) reacted with (Rh{sub 2}(CO){sub 4}Cl{sub 2}) to give the novel dinuclear adducts (C{sub 5}Me{sub 5}Rh(Me)(CO){l brace}x-C{sub 5}H{sub 4}NRh(CO){sub 2}Cl{r brace}), in which a 3- or a 4-pyridyl bridges Rh(III) and Rh(I). An X-ray determination of (C{sub 5}Me{sub 5}Rh(Me)(CO){l brace}3-C{sub 5}H{sub 4}NRh(CO){sub 2}Cl{r brace}) confirmed the structure.« less
  • The complexes (C/sub 5/Me/sub 5/)Rh(PMe/sub 3/)(R)X(R=Me(CH/sub 3/),Ph-)Phenyl), p-tolyl,3,4-C/sub 6/H/sub 3/Me/sub 2/, 2,5-C6H/sub 3/Me2, and C=CH=CHgreater than or equal to-CH/sub 2/-CH/sub 2/;X=Br) react with hydride doners Li(HB(sec-Bu/sub 3/ (butyl)) or Na/sup +/(H/sub 2/Al(OCH/sub 2/CH/sub 2/CH/sub 2/OCH/sub 3/)/sub 2/)-to produce (C/sub 5/Me5)Rh(PMe/sub 3/)(R)H. The complexes with R=alkyl or R=vinyl are unstable, undergoing rapid reductive elimination at 25/sup 0/C, but can be observed by /sub 1/H NMR below -20/sup 0/C. (C/sub 5/Me/sub 5/)Rh(PMe/sub 3/)(CH/sub 3/)H undergoes first-order reductive elimination with k=(6.38 +/-0.10) X 10/sup -5/ s/sup -1/ at -17/sup 0/C. In contrast, (c/sub 5/Me/sub 5/)Rh(PMe/sub 3/)(C/sub 6/H/sub 5/)h undergoes a more complicated first-ordermore » process in C/sub 6/D/sub 6/, producing C/sub 6/H/sub 6/ and (C/sub 5/Me/sub 5/)Rh(PMe/sub 3/)(C/sub 6/D/sub 5/)D with the overall activation parameters delta H/sup +/=30.5 +/- 0.8 kcal/mol and ..delta..S/sup +/=14.9+/- 2.5 eu. The alkyl and aryl hydride complexes can also be generated by photochemical extrusion of H/sub 2/ from (C/sub 5/Me/sub 5/)Rh(PMe/sub 3/)H/sub 2/ in the presence of alkane or arene solvent. In a competition experiment, a 5.4:1 selectivity for benzene over cyclopentane was exhibited at -35/sup 0/C. Irradiation in toluene solvent at -45/sup 0/C produced products in which activation of all possible C-H bonds of toulene was observed 57% meta, 36% para, 7% ortho, and <1% benzyl. Thermodynamically controlled competition between activation of benzene and tolune, m-xylene, o-xylene, or p-xylene showed preferences for benzene of 2.7, 12.1, 7.6, and 58.6. The aryl complexes (C/sub 5/Me/sub 5/)Rh(PMe/sub 3/)(aryl)H were found to be in rapid equilibrium with their ..nu../sup 2/-arene derivatives at temperatures above -15/sup 0/C. Mechanistic studies revealed a (1,2)-shift pathway around the ring with ..delta..H/sup +/ =16.3 +/- 0.2 kcal/mol and ..delta..S/sup +/ =-6.3 +/- 8 eu for derivative with R=2,5-C/sub 6/H/sub 3/Me/sub 2/.« less
  • No abstract prepared.
  • A practical, functional group tolerant method for the Rh-catalyzed direct arylation of a variety of pharmaceutically important azoles with aryl bromides is described. Many of the successful azole and aryl bromide coupling partners are not compatible with methods for the direct arylation of heterocycles using Pd(0) or Cu(I) catalysts. The readily prepared, low molecular weight ligand, Z-1-tert-butyl-2,3,6,7-tetrahydrophosphepine, which coordinates to Rh in a bidentate P-olefin fashion to provide a highly active yet thermally stable arylation catalyst, is essential to the success of this method. By using the tetrafluoroborate salt of the corresponding phosphonium, the reactions can be assembled outside ofmore » a glove box without purification of reagents or solvent. The reactions are also conducted in THF or dioxane, which greatly simplifies product isolation relative to most other methods for direct arylation of azoles employing high-boiling amide solvents. The reactions are performed with heating in a microwave reactor to obtain excellent product yields in two hours.« less