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- Title
Practical Synthesis of [ n]Cycloparaphenylenes ( n=5, 7-12) by H<sub>2</sub>SnCl<sub>4</sub>-Mediated Aromatization of 1,4-Dihydroxycyclo-2,5-diene Precursors.
- Authors
Patel, Vijay Kumar; Kayahara, Eiichi; Yamago, Shigeru
- Abstract
Cyclic precursors of cycloparaphenylenes (CPPs) containing 1,4-dihydroxy-2,5-cyclohexadien-1,4-diyl units are prepared by modifying a synthetic method developed by Jasti and co-workers for the synthesis of corresponding 1,4-dimethoxy derivatives. Reductive aromatization of the diyl moieties by SnCl2/2 HCl takes place under mild conditions and affords the CPPs in good yields, incorporating 5 or 7-12 phenylene units. Highly strained [5]CPP is synthesized in greater than 0.3 g scale. 119Sn NMR spectroscopy clarifies the in situ formation of an ate complex, H2SnCl4, upon mixing a 2:1 ratio of HCl and SnCl2, which serves as a highly active reducing agent under nearly neutral conditions. When more than 2 equivalents of HCl, in relation to SnCl2, are used, acid-catalyzed decomposition of the CPP precursors takes place. The stoichiometry of HCl and SnCl2 is critical in achieving the desired aromatization reaction of highly strained CPP precursors.
- Subjects
DIHYDROXYACETONE; CYCLOALKANES; MOIETIES (Chemistry); AROMATIZATION; CHEMICAL precursors; STOICHIOMETRY
- Publication
Chemistry - A European Journal, 2015, Vol 21, Issue 15, p5742
- ISSN
0947-6539
- Publication type
Article
- DOI
10.1002/chem.201406650