SYNTHESIS AND CONFORMATIONAL STUDIES OF TETRAHYDROXY[3.1.3.1]METACYCLOPHANES AND ELECTROPHILIC AROMATIC-SUBSTITUTION OF THEIR TETRAMETHOXY DERIVATIVES

Base-catalysed condensation of 1,3-bis(5-tert-butyl-2-hydroxyphenyl)pr opane 5 with formaldehyde in xylene has been carried out to form the n ovel propane-bridged calixarene-type macrocyclic compound, tetrahydrox y[3.1.3.1]metacyclophane 6. The optimum yield (90%) of 6 is obtained w ith NaOH as the base, the use of other alkali-metal hydroxides giving lower yields. AlCl3-MeNO2-catalysed trans-tert-butylation of 6 in benz ene affords 7 in 80% yield. Intramolecular hydrogen bonding has been o bserved in the tetraols 6 and 7 as comparable to calix[4]arene. Methyl ation of 7 with Mel affords the tetramethoxy derivative 11a. The stabi lity of multi-membered carbon skeletons permits the interconversion of functional groups at the lower and upper rims without special regard to ring-opening side-reactions on the upper rim. For example, the intr oduction of Br, formyl and acetyl substituents has been achieved by el ectrophilic aromatic substitution of the tetramethoxy derivative 11a. The H-1 NMR spectral behaviour of these macrocycle metacyclophanes is also discussed.