Spirodienone derivatives of a spherand-type calixarene

Oxidation of the spherand-type calixarene 4 with 1 or 2 equiv of phenyltrim ethylammonium tribromide/base afforded mono- and bis(spirodienone) derivati ves (8b and 9, respectively). The spirodienone groups are derived from the oxidation of two phenols connected by a common methylene group. NOESY data indicated that 9 possesses a "head to tail" arrangement of the spirodienone groups. Oxidation of 4 with 3 equiv of the oxidizing reagent afforded two tris(spirodienone) calixarene derivatives 11 and 10 with C-1 and C-3 symmet ries, respectively. The same tris(spirodienone) products were obtained by o xidation of 9 with I-2/aq KOH. Tris(spirodienone) 11 displayed NOE cross-pe aks in the NOESY NMR spectrum consistent with a nonalternant disposition of carbonyl and ether groups. Upon heating 10 and 11 isomerize in the solid s tate and in solution. The major component in the equilibration mixtures is 11, indicating that this is the thermodynamically more stable tris(spirodie none) isomer.