The first examples of singly bridged calix[7]arenes 2-4 have been obtained by base-promoted direct O-alkylation of p-tert-butylcalix[7]arene with a variety of bis-electrophiles including BrCH2Cl, oligoethylene glycol ditosylates, and 1,4-bis(bromomethyl)benzene. 1,2-Bridging was favored with 'short bite' spanning elements, while the 1,4-isomer predominated with the others (yields up to 72% in the presence Of Cs2CO3). Assignment of bridging pattern was mainly based on chemical shift of OH groups, in some cases confirmed by 2D NMR experiments. A hampered conformiational mobility, depending on the position and nature of the bridge, was observed for compounds 2-4
Regioselective intramolecular bridging of p-tert-butylcalix[7]arene
MARTINO, Marco;GAETA, CARMINE;NERI, Placido
2002-01-01
Abstract
The first examples of singly bridged calix[7]arenes 2-4 have been obtained by base-promoted direct O-alkylation of p-tert-butylcalix[7]arene with a variety of bis-electrophiles including BrCH2Cl, oligoethylene glycol ditosylates, and 1,4-bis(bromomethyl)benzene. 1,2-Bridging was favored with 'short bite' spanning elements, while the 1,4-isomer predominated with the others (yields up to 72% in the presence Of Cs2CO3). Assignment of bridging pattern was mainly based on chemical shift of OH groups, in some cases confirmed by 2D NMR experiments. A hampered conformiational mobility, depending on the position and nature of the bridge, was observed for compounds 2-4I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
