期刊
ORGANOMETALLICS
卷 28, 期 12, 页码 3518-3531出版社
AMER CHEMICAL SOC
DOI: 10.1021/om900286x
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资金
- Research Corporation
- Natural Sciences and Engineering Research Council of Canada (NSERC
- AstraZeneca Canada Inc
- Merck Frosst Centre for Therapeutic Research
- Boehringer Ingelheim (Canada) Ltd.
- Canadian Foundation for Innovation
- Ontario Innovation Trust
- University of Waterloo
- Government of Quebec (FCAR)
- Government of Ontario (OGS). RIC
- Magnus Ehrntooth Foundation
- Oulu University Scholarship Foundation
- Alfred Kordelin Foundation
A full account of the Pd-catalyzed intramolecular reactions of (E)-2,2-disubstituted 1-alkenyldimethylalanes with aryl triflates as an entry into polycarbocyclic structures displaying an ethyl-methylsubstituted all-carbon benzylic quaternary center is herein presented. It was found that the efficiency of the Pd-catalyzed carbon-carbon bond forming process is highly affected by the structure of the starting material, including tether length and aryl substitution pattern; substituting the position ortho to the triflate is mandatory to obtain a good yield of the carbocycle. Moreover, the formation of 1-ethyl-1-methylindanes is facile in comparison to the case for the analogous tetrahydronaphthalenes, for which the competing methyl cross-coupling reaction is equally competent. It was established through labeling studies that the carbon-carbon bond forming events are stereospecific and proceed though the intermediacy of a neopentylic sp(3)-gem-dimetallic palladio(II) dialkylaluminoalkane species, from which a 1,2-methyl migration from aluminum to carbon occurs. Intramolecular palladium-catalyzed reactions of 1-naphthyl triflates with (E)-2,2-disubstituted 1-alkenyldimethylalanes revealed two competing reaction pathways: arylation with sequential 1,2-alkyl migration from aluminum to carbon and intramolecular 1,2-diarylation, in which the catalytic cycle is terminated by direct arylation of the C(sp(3))-Pd(II) bond. Factors such as tether length, additives, solvent polarity, and C-H center dot center dot center dot Pd interactions between the Pd(II) center and the hydrogen atom at the 8-position all influence not only the pathway taken by the (sigma-aryl)palladium(II) complexes but also the subsequent reactivity of the ((T-alkyl)palladium(II) complexes.
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