The Synthesis and Photo-Induced Deprotection Reaction of Calix[4]resorcinarene Derivatives Containing t-Butyl Ester Moieties

The syntheses and photoinduced deprotection reactions of calix[4]resorcinarene derivatives with pendant t-butyl ester moieties were examined. Calix[4]resorcinarenes, 1a-1h, were prepared by the condensation reaction of resorcinol with certain aldehydes in the presence of hydrochloric acid as a catalyst in ethanol at 80 °C for 30 min in good yields. The substitution reaction of 1a-1h with t-butyl bromoacetate using cesium carbonate as a base and tetrabutylammmonium bromide (TBAB) as a phase transfer catalyst was performed to afford the corresponding calix[4]resorcinarene derivatives, 2a-2h with pendant t-butyl ester groups. It was found that 2a, 2e, 2f, 2g, and 2h had film forming properties. The photoinduced deprotection reaction of calixarene derivatives 2a, 2e, 2f, 2g, and 2h was examined in the presence of bis-[4-(diphenylsulfonio)phenyl] sulfide (DPSP) as a photoacid generator in the film state upon UV irradiation for 5 min followed by heating at 170 °C. It was found that the deprotection reaction of the t-butyl ester groups of 2a, 2e, 2f, 2g, and 2h proceeded smoothly to produce the corresponding calixarene derivatives, 3a, 3e, 3f, 3g, and 3h with carboxylic acid groups, quantitatively.