CALIXARENES .40. ARYLMETHYLENATION OF P-(CYANOMETHYL)CALIX[4]ARENE

Treatment of tetra-O-substituted p-(cyanomethyl)calix[4]arenes 3 and 6 with aromatic aldehydes yields aldol product resulting from condensation at the carbons a to the cyano groups. The products 4 from the tetra-O-benzyl compound 3 retain the benzyl groups and are formed in the 1,3-alternate conformation. The products 7 from the tetra-O-benzoyl compounds 6, however, involve loss of the benzoyl groups and are formed in the cone conformation. The same phenolic compounds 7 can be obtained from the O-benzyl compounds 4 by Lewis acid-induced removal of the benzyl groups. Reintroduction of the benzyl groups by treating 7 with benzyl bromide produces the tetra-O-benzylated product in the cone conformation (12) when NaH is used as the base or in the 1,3-alternate conformation (4) when K2CO3 is used as the base. Benzoylation of 7 produces the tetra-O-benzoyl compound in the 1,3-alternate conformation (10) when 1-methylimidazole is used as the base or the 1,3-di-O-benzoyl compound in a flattened cone conformation (11) when AlCl3 is used as the catalyst. H-1 NMR and C-13 NMR data provide support for the conformational assignments, and UV data suggest a twisting of the conjugated system in the 2'-substituted compounds 4b/7b (2'-methoxyphenyl), 4e/7e (2'-methylphenyl), and 4g/7g (2'-chlorophenyl).