Browsing by Author "Shu, CM"

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Calix[4]arenes with a lid in their upper rims: 1,3-dipolar cycloaddition reactions of benzonitrile oxides with 5-allyl-, 5,11-dially- and 5,17-diallylcalix[4]arenes
(2000-02-01)
Shu, CM
;
Lin, WL
;
Lee, GH
;
Peng, SM
;
Chung, WS
The upper rim substituted mono- and diisoxazolinomethylcalix[4]arenes 9-23 are synthesized in good yields from 1,3-dipolar cycloaddition reactions of para-substituted phenyl nitrileoxides with 5-allyl-, 5,11-diallyl- and 5,17-diallycalix[4]arenes 5-7; the structures of 9-23 are consistent with a 'cone' conformation and the 'vase-with-a-lid' structure of 11 was confirmed by a single-crystal x-ray analysis. Preliminary results show that the monoisoxazolinomethylcalix[4]arene can form an inclusion complex with ammonium cation.
Synthesis of calix[4]arenes with four different "lower rim" substituents
(1999-04-16)
Shu, CM
;
Chung, WS
;
Wu, SH
;
Ho, ZC
;
Lin, LG
Calix[4]arenes with four different "lower rim" substituents were synthesized following six-step sequences. The first alkyl group (R-1) was introduced using R1X and CH3ONa, and then reaction with R2X and K2CO3 led to the introduction of a second alkyl group (R-2) at the 3-position. Benzoate was introduced as a protecting group at the 1,3-O-disubstituent stage and was removed under basic conditions after the incorporation of the third alkyl group (R-3) With R3X and NaH, The final alkyl group (R-4) was introduced with R4X and NaH to give the chiral title compounds.
Upper rim allyl- and arylazo-coupled calix[4]arenes as highly sensitive chromogenic sensors for Hg2+ ion
(2005-04-15)
Kao, TL
;
Wang, CC
;
Pan, YT
;
Shiao, YJ
;
Yen, JY
The syntheses and chromogenic properties of calix[4]arenes, carrying 5,17-bisallyl-11,23-bis(p-X-phenyl)azo 3a-c, 5,11,17-triallyl-23-(p-X-phenyl)azo 4a-c, and 5,17-bis(hydroxypropyhl)-11,23-bis(p-X-phenyl)azo groups on the upper rims 5a,b, are described. Unexpectedly, UV/vis spectra of the very popular 4-(4-nitrophenyl)azophenol-coupled calix[4]arenes 3c and 4c did not show any shift in lambda(max) when 10 different metal perchlorates were added separately to the host in a methanol-chloroform (v/v = 1/399) cosolvent. In contrast, the absorption spectra of calix[4]arenes with either 4-methoxyphenylazo (3b-5b) or 4-phenylazo (3a-5a) on the upper rim showed substantial batho-chromic shifts (Delta lambda = 128-162 nm) upon the addition of soft metal ions (such as Hg2+, Cr3+, and Cu2+). The 4-(4-methoxyphenyl)azophenol-coupled calix[4]arenes (the 3b-5b series) are found to be highly sensitive for mercury ion (Hg2+) among the 10 different metal ions screened. Strong interactions between Hg2+ ion and the 4-(4-methoxyphenyl)azophenol(s) as well 18 the p-allyl groups, are corroborated by the H-1 NMR studies of 3a,b center dot Hg2+ complexes. Furthermore, Job's plots revealed 1:1 binding stoichiometry for all these p-allyl- and arylazo-coupled calix[4]arenes with transition metal ions, and Benesi-Hilderbrand plots were used for the determination or their association constants.