Part I. Synthesis of coumarin-based heterobicycles and their potential applications Part II. Synthesis of fluorescence via MCRs and its application of fluorescence redox switches

• Main Authors: Jiun-Ting Lai, 賴俊廷
• Other Authors: Ding-Yah Yang
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/86617572600722659010

碩士 === 東海大學 === 化學系 === 96 === Part I. Synthesis of coumarin-based heterobicycles and their potential applications A series of bicyclic derivatives were prepared in three to four steps from p-anisidine and substituted benzaldehyde. The key step of the synthesis involved the acid-catalyzed coupling of 4-hydroxcoumarin or 4-aminocoumarin derivatives with amino alcohols 11, 14, 16 to give the ring-opened forms 12, 17, 20 and the ring-closed forms 15, 21. When 4-alkylaminocoumarins were used as the coupling reagents, the major cyclized product was 21, rather than the corresponding N-alkylated products. Alternatively, compounds 17, 20, 21 was cyclized by DDQ oxidation to produce the quinone imines 18, 22. The molecular structures of the synthesized compounds were characterized by X-ray crystallography. Part II. Synthesis of the oxazabicyclic via MCRs and it’s application of fluorescence redox switches A practical protocol for the preparation of a parallel solution-phase library of oxazabicycle is reported. Target compounds were obtained in moderate to good yields by a Yb(OTf)3-catalyzed, one-pot domino reaction from various anisidines, aryl aldehydes, isobutyraldehyde, and 4-hydroxycoumarins/dimedone. Purification of the final products by either recrystallization in ethyl acetate/methylene chloride or column chromatography allowed easy isolation of components of the array. a coumarin-based oxazobicyclic derivative 7h was efficiently synthesized as a novel fluorescence redox switch. The emission of the coumarin was found to be quenched by the aromatic amine, which had solvent effect when the fluorophore and the quencher were covalently connected via a rigid oxazobicyclic ring, the sodium borohydride-induced ring-opening of the heterobicyclic moiety results in a distinct decrease of the emission intensity. The resulting ring-opened form 8h can be reverted to the original fluorescence ring-closed form 7h via H2O2 oxidation. The fluorescence of the oxazobicycle can be chemically switched ON and OFF through the ring-closing and ring-opening of the heterobicyclic moiety.