Selective mono-O-acylation of C2V-symmetrical calix[4]arenediols with acylisocyanates.

Calix[4]arenedialkyl ethers 3 react with an excess of acylisocyanates to give selectively monoacylated products 4. Intramolecular hydrogen bonds and steric effects of the acylcarbamate fragments are most likely responsible for the high selectivity of this monoprotection. [reaction: see text]