Synthesis of p-tert-butylcalix[4]arene derivatives with trans-alkyl substituents on opposite methylene bridges.
Reaction of the bis(spirodiene) calixarene derivative 9 possessing exocyclic double bonds with tetraethylammonium fluoride or chloride afforded bis(spirodienone) calixarene derivatives substituted by the corresponding halogen atoms (11 and 12). Reaction of 9 with alkyl cuprates yielded in one step p-tert-butylcalix[4]arene derivatives with opposite methylene groups substituted in a trans fashion by identical alkyl substituents (methyl, ethyl, or isopropyl). The isopropyl derivative 16 displayed the largest cone-to-cone inversion barrier of the series.
Simaan
Samah
S
Department of Organic Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.
Biali
Silvio E
SE