Diester intrabridging of p-tert-butylcalix[8]arene and unexpected formation of the monospirodienone derivative

Reaction of p-tert-butylcalix[8]arene 1 with adipoyl chloride in the presence of NaH as the base yielded singly and doubly intrabridged esters 2–4 and 6. Surprisingly, calix[8]arene monospirodienone derivative 7 was also isolated, which was originated by O2 oxidation. The conditions of this oxidation were optimized leading to a novel synthetic approach to calixarene monospirodienones based on the O2/NaH/acyl-chloride oxidizing system. Xantheno calix[8]arenes 8–8a were obtained by rearrangement of 7.