Functionalization of benzylic carbon-hydrogen bonds. Mechanism and scope of the catalytic synthesis of indoles with [Ru(dmpe)[sub 2]]
- Univ. of Rochester, NY (United States)
A unique route for the synthesis of indoles from o-tolyl isocyanides using Ru(dmpe)[sub 2](H)-(naphthyl) and Ru(dmpe)[sub 2]H[sub 2] as catalysts has been examined. The scope of this method for indole preparation has been examined with a variety of o-tolyl isocyanides, including 3-, 4-, and 5-R-o-tolyl isocyanides (where R = methyl, methoxy, or fluoro), 2,6-xylyl isocyanide, 2,6-diethylphenyl isocyanide, 2-ethylphenyl isocyanide, o-tolyl isocyanide, and 6-ethyl-o-tolyl isocyanide. The mechanism of indole formation has been investigated using kinetic and isotope effect experiments to differentiate key product-determining steps of the cycle. Results are consistent with a mechanism involving irreversible CNR coordination prior to intramolecular oxidative addition of the o-methyl C-H bond. Competitive isotope effect studies using d[sub 0]- and [alpha],[alpha],[alpha],[alpha]',[alpha]',[alpha]', 3, 5-d[sub 8]-labeled 4-tert-butyl-2,6-xylyl isocyanides indicate virtually no isotope effect (k[sub H]/k[sub D] = 1.08) when the selection of which bond to active is intermolecular. Use of 4-tert-butyl-2,6-xylyl-[alpha],[alpha],[alpha]-d[sub 8] isocyanide shows that C-H activation is faster than C-D activation (k[sub H]/k[sub D] = 2.6) in an intramolecular competition, where the choice of C-H and C-D bonds to activate is within one xylyl isocyanide. The reaction with 2,6-diethylphenyl isocyanide to give 3-methyl-7-ethylindole is first order in [Ru(dmpe)[sub 2](H)(naphthyl)] and zero order in [CNR]. 27 refs., 5 figs., 3 tabs.
- DOE Contract Number:
- FG02-86ER13569
- OSTI ID:
- 5116375
- Journal Information:
- Organometallics; (United States), Vol. 13:1; ISSN 0276-7333
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
INDOLES
SYNTHESIS
AROMATICS
CATALYSIS
CHEMICAL BONDS
EXPERIMENTAL DATA
INDAZOLES
ISOTOPES
NUCLEAR MAGNETIC RESONANCE
PYRAZOLES
PYRROLES
PYRROLIDINES
RUTHENIUM COMPLEXES
X-RAY DIFFRACTION
AMINES
AZAARENES
AZOLES
COHERENT SCATTERING
COMPLEXES
DATA
DIFFRACTION
HETEROCYCLIC COMPOUNDS
INFORMATION
MAGNETIC RESONANCE
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
RESONANCE
SCATTERING
TRANSITION ELEMENT COMPLEXES
400201* - Chemical & Physicochemical Properties
400102 - Chemical & Spectral Procedures