CYCLIZATION AND REDUCTIVE CLEAVAGE OF MONOSPIRODIENONE CALIX[4]ARENE DERIVATIVES - TRIHYDROXY-P-TERT-BUTYLCALIX[4]ARENE REVISITED

The monospirodienone derivative of a-tert-butyl-25,26,27,28-tetrahydro xycalix[4]arene (2) undergoes in the presence of an ammonium tribromid e salt a spiroannulation reaction at the alpha-position to the carbony l. Reaction of 2 with an equimolar amount of LA followed by treatment with a phosphorylating agent yielded a monosubstituted spirodienone. R eductive cleavage of the latter (K/NH3) afforded ,23-tetra-tert-butyl- 25,26,27-trihydroxycalixarene (10). The structure of 10 was corroborat ed indirectly by X-ray crystallography of its bromo dispiro derivative 11. It is concluded that the compound obtained by cleavage of the bis (diethyl phosphate) ester derivative 13, and previously described by u s as 10, is rt-butyl-25,27-dihydroxy-26-monoaminocalix[4]arene (12). T he latter readily forms a tosylate salt in CDCl3 solution. Considering this reassignment, the inversion barriers of several OH-depleted amin ocalixarenes and their salts are reexamined.