Selective Arylmethylation, Arylmethenylation and Aroylation of Mono- and Tetra-p-Cyanomethylcalix[4]arene
作者:Shiv Kumar Sharma、Iftikhar Alam、C. David Gutsche
DOI:10.1055/s-1995-4075
日期:1995.9
Tetra-p-cyanomethylcalix[4]arene (3) is selectively converted to its tetrabenzyl ethers 4 (1,3-alternate conformer) and 1,3-dibenzyl ethers 5 (cone conformer) by reaction with benzyl halides in the presence of variable amounts of potassium carbonate. Mono-p-cyanomethylcalix[4]arene (6) gives exclusively the cone conformer of the 1,3-disubstituted product 7 (benzyl moiety attached to the unsubstituted rings). Aroylation of 6 in the presence of sodium hydride gives tetrasubstituted product 9, whereas with aluminum chloride it produces an easily separable mixture of 1,3-disubstituted compounds 10 and 11. Surprisingly, no regioselectivity is achieved using 1-methylimidazole as the base. On the other hand, 6 reacts with 4-bromobenzenesulfonyl chloride under the same reaction conditions to produce the cone conformer of the tetrasubstituted product 12. Reactions of 6 with benzyl halides or benzaldehydes using sodium hydride as a base give the fully benzylated compounds 8 or the benzal derivatives 13, respectively.
Upper Rim Substitution of Calixarenes: Carboxylic Acids
作者:Shiv Kumar Sharma、Suseela Kanamathareddy、C. David Gutsche
DOI:10.1055/s-1997-1359
日期:1997.11
The mono- (5a), bis- (4a and 4b), and tetrakis (1a)-p-cyanomethylcalix[4]arenes as well as the bis(cyanomethyl)calix[6]arene (6a) have been transformed both by acid and base induced hydrolysis to the corresponding p-carboxymethylcalix[4]arenes 5b, 4c, 4d, 2a, and 6b which, in turn, were converted to the methyl (5c, 4e, 4f, 2b) and ethyl (5d, 4g, 2c) esters. The cyanomethyl groups in the sterically hindered compounds 7 and 8 and their corresponding monomers 10 and 11, however, were inert to hydrolysis, even under strenuous conditions. The methyl ester 2b can be converted to the 1,3-dibenzyl ether (3b) and the 1,3-dibenzoate (3c) as well as the tetrabenzyl ether (3a) and tetrabenzoate (3d).