The metal template effect on O-alkylation of tetrahydroxy[3.1.3.1]metacyclophane with 4-(chloromethyl)pyridine to afford tetrakis- [(4-pyridylmethyl)oxy][3.1.3.1]metacyclophanes and their conformational studies
| Autor: | Takehiko Yamato, Kenji Kumamaru, Hirohisa Tsuzuki |
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| Rok vydání: | 2001 |
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| Zdroj: | Canadian Journal of Chemistry. 79:1422-1430 |
| ISSN: | 1480-3291 0008-4042 |
| Popis: | An attempted O-alkylation of the flexible macrocycle tetrahydroxy[3.1.3.1]metacyclophane (1) with 4-(chloromethyl) pyridine (2a) in the presence of NaH under THF reflux gave 1,3-di-O-substitution product distal-3a as a major product. In contrast, tetraol 1 was O-alkylated with 2a in the presence of Cs2CO3 to afford a mixture of two conformers of tetra-O-alkylated product 4a in a ratio of 77:23 (1,4-alternate-4a:partial-cone-4a) in 95% yield. No formation of the cone conformer in the reaction of the tetraol 1 with 2a, in comparison with those with 2-(chloromethyl) pyridine (2b) or benzyl bromide (2c) in the presence of NaH or K2CO3, which predominantly afforded cone-conformer, might be attributable to the absence of contributions derived from cationN interactions as well as cationπ interactions. The latter effect might be much smaller because of the decreased π-density of the pyridine ring compared to that of the benzene ring. The structural characterization of these products in solution as well as solid state is also discussed.Key words: macrocycles, calixarenes, cyclophanes, [3.1.3.1]metacyclophanes, O-alkylation, conformation, crystal structure, cationN interaction. |
| Databáze: | OpenAIRE |
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