Methylation of p-tert-butylcalix[8]arene. Products obtained in the presence of strong bases

Methylation of p-tert-butylcalix[8]arene with MeI in the presence of strong bases (NaH, BaO/Ba- (OH)2, or Cs2CO3) in THF has been investigated. Composition of the reaction mixtures differs remarkably from those obtained using weak bases and described in a preceding paper. Several previously unreported methylated products [two dimethoxy- (21,5 and 21,4), a trimethoxy- (31,2,5), a tetramethoxy- (41,2,3,6), two pentamethoxy- (51,2,3 and 51,2,4), and three hexamethoxy- (61,2, 61,3, and 61,4)] have been isolated. In many cases the substitution pattern was assigned unambiguously on the basis of spectroscopic evidence only, while in others chemical correlation with known compounds was required.