Direct Regioselective Formylation of Tetraalkoxycalix[4]arenes Fixed in the Cone Conformation and Synthesis of New Cavitands
作者:Arturo Arduini、Stefano Fanni、Giuseppe Manfredi、Andrea Pochini、Rocco Ungaro、Anna R. Sicuri、Franco Ugozzoli
DOI:10.1021/jo00110a054
日期:1995.3
Regioselectivity of the formylation of tetraalkoxycalix[4]arene fixed in the cone conformation has been studied. Direct, diametrical (1,3) diformylation of calix[4]arenes having four chelating chains at the lower rim has been achieved. Simple tetraalkoxycalix[4]arenes produce a mixture of diametrical (1,3) and proximal (1,2) diformylated products. The (1,3) functionalized compounds have been used for the synthesis of double calix[4]arenes 12a,d linked via the upper rim. The residual mobility of these cone conformers is indicated by the X-ray crystal structure of compound 12d, which shows a flattened cone conformation, and by the reactive behavior of 1,3-bis(hydroxymethyl) derivatives 9a,d which give very distorted 1,3-bridged compounds 11a,d, through an intramolecular cyclization process.