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DOI: 10.1055/s-2007-968783
Carbomer of Benzene - A Tour de Force
Rezensent(en):Timothy M. Swager, Koushik VenkatesanLaboratoire de Chimie de Coordination of the CNRS, Toulouse, France
Hexasilylated Total Carbomer of Benzene
Angew. Chem. Int. Ed. 2007, 46: 4337-4341
Publikationsverlauf
Publikationsdatum:
24. Juli 2007 (online)
Key words
alkynes - aromaticity - carbobenzenes
Significance
Chauvin and co-workers report the first synthesis of hexaalkynyl [6]pericyclyne and carbobenzene. The selected method involves an [8+10] ring formation that proved to be efficient for the preparation of other [6]pericyclynes. The final step in the synthesis is a reductive aromatization that was achieved by the use of only two equivalents of Co2(CO)8. Subsequent treatment with SnCl2/HCl and direct oxidative decomplexation with ceric ammonium nitrate (CAN) afforded the hexaalkynyl carbobenzene in 12% yield over three steps. The 1H NMR spectrum showed that the triethylsilyl groups are particularly deshielded as a result of a remote ring-current effect. The attempted desilylation of hexa(trialkylsilyl) carbobenzene with tetrabutylammonium fluoride afforded only insoluble black material.
Comment
The synthesis of carbobenzene reported by the authors via a hexaalkynyl [6]pericyclyne demonstrates the power of organic chemistry to synthesize complex structures. The stereochemical resolution of hexaalkynyl [6]pericyclyne and its crystal packing open new horizons for the syntheses of novel expanded carbon nanotubes. The controlled desilylation of the reported carbobenzene could lead to a genuine carbomer of benzene or to novel carbon allotropes derived from deprotected carbobenzene. Carbobenzene-type systems might interact with gas molecules in a selective fashion and thereby have potential applications in sensors as previously reported for macrocycles (T. Naddo, Y. Che, W. Zhang, K. Balakrishnan, X. Yang, M. Yen, J. Zhao, J. S. Moore, L. Zhang J. Am. Chem. Soc. 2007, 129, 6978).