A Convenient Preparation ofC-Silylated Calixarenes

Calix[4]arenes having multiple silyl groups on the upper (wide) rim were prepared from the corresponding bromocalixarenes by halogen-metal exchange with t-BuLi followed by silylation. The best results were obtained using the clear supernatant from a mixture of chlorosilane and triethylamine. With the higher molecular weight chlorosilanes, an aqueous workup was replaced by a filtration through a column of silica gel. p-(Trimethylsilyl)calixarene 17, the silicon analogue of the well-studied p-tert-butylcalixarene 1, formed a crystalline complex with toluene having a toluene molecule in the cone cavity with the toluene methyl protruding out at an angle.