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), Journal Name: Organometallics; (United States) Vol. 13:1; ISSN 0276-7333; ISSN ORGND7
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400102 -- Chemical & Spectral Procedures
400201* -- Chemical & Physicochemical Properties
AMINES
AROMATICS
AZAARENES
AZOLES
CATALYSIS
CHEMICAL BONDS
COHERENT SCATTERING
COMPLEXES
DATA
DIFFRACTION
EXPERIMENTAL DATA
HETEROCYCLIC COMPOUNDS
INDAZOLES
INDOLES
INFORMATION
ISOTOPES
MAGNETIC RESONANCE
NUCLEAR MAGNETIC RESONANCE
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PYRAZOLES
PYRROLES
PYRROLIDINES
RESONANCE
RUTHENIUM COMPLEXES
SCATTERING
SYNTHESIS
TRANSITION ELEMENT COMPLEXES
X-RAY DIFFRACTION