CONVENIENT ONE POT PROCEDURE FOR SYNTHESIS OF FORMYLATED CALIX[n]ARENES

One-pot Selective Formylation and Claisen Rearrangement on Calix[4]arenes

“…Formylation using hexamethylenetetraamine (hexamine) in glacial acetic acid [8] or trifluoroacetic acid [3] (Duff reaction) has also been reported, but has not been used for selective formylation. Chawla et al [3] have triformylated the upper ring of a disubstituted calix [4]arene using these conditions. The same conditions have been used to convert the upper-rim bromomethylcalix [4]arene to the tetraformyl derivative in good yield (Sommelet reaction) [5].…”

“…Chawla et al [3] have triformylated the upper ring of a disubstituted calix [4]arene using these conditions. The same conditions have been used to convert the upper-rim bromomethylcalix [4]arene to the tetraformyl derivative in good yield (Sommelet reaction) [5]. We were interested in developing a convenient procedure for selective formylation that avoided the use of the carcinogenic and volatile dichloromethyl methyl ether.…”

“…We were interested in developing a convenient procedure for selective formylation that avoided the use of the carcinogenic and volatile dichloromethyl methyl ether. We report here the use of the Duff reaction for the selective formylation of diallyl and dipropyl-calix [4]arenes.…”

“…Therefore, it was expected that the formylation of the diallylcalix [4]arene (1) [9] would provide the diformylcalix [4]arene (2) or, if the alkoxy-substituted rings were not sufficiently deactivated, the tetraformyl derivative. Treatment of (1) with twenty equivalents of hexamine in glacial acetic acid at reflux gave, after hydrolysis, a product with an IR spectrum that clearly indicated that formylation had occurred (y ¼ 1686 cm 21 ).…”

“…The efficient and selective introduction of reactive functional groups on to the macrocycle is therefore of interest, as indicated by the number of recent papers focused on the formylation of the upper rim of the calixarene [1 -8]. Many of these employ the Gross formylation where the electrophilic reaction of dichloromethyl methyl ether is promoted by a Lewis acid [2,4,6]. Formylation using hexamethylenetetraamine (hexamine) in glacial acetic acid [8] or trifluoroacetic acid [3] (Duff reaction) has also been reported, but has not been used for selective formylation.…”