Synthesis of novel calix[4]arenes containing organosilicon groups

Metalation of (RSiMe₂)₃CH (1a R = H, 1b R = Me, 1c R = Ph) with lithium diisopropylamide (LDA) or methyllithium in THF gave organolithium reagents (RSiMe₂)₃CLi, which reacted with the formylated calixarene (2), to give the corresponding 5,17-bis2,2-bis(organosilyl)-1-ethenyl]-25,26,27,28-tetrapropoxycalix4]arenes (3a, 3b and 3c) via the Peterson olefination. The compounds (RSiMe₂)₃CLi were treated with 25,26,27,28-tetrakis(4-bromobutoxy)calix4]arene (4) to give 25,26,27,28-tetrakis4-(tris(dimethylsilyl)methyl)butoxy] calix4]arene (5a) and 25,26,27,28-tetrakis4-(tris(trimethylsilyl)methyl)butoxy] calix4]arene (5b) via nucleophilic substitution reactions. However the compound 25,26,27,28-tetrakis4-(tris(dimethylphenylsilyl)methyl)butoxy] calix4]arene (5c) was not obtained, presumably because (PhSiMe₂)₃C- is highly sterically hindered and the reactivity of its derivatives is low. The compound 5a has potential as a core for dendrimers.