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Photoreduction and Ketone‐sensitized Reduction of Alkaloids
Author(s) -
Görner Helmut,
Miskolczy Zsombor,
Megyesi Mónika,
Biczók László
Publication year - 2011
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.2010.00880.x
Subject(s) - chemistry , sanguinarine , photochemistry , ketone , quantum yield , berberine , acetonitrile , singlet oxygen , palmatine , solvent , radical , triplet state , triethylamine , photodissociation , oxygen , fluorescence , alkaloid , organic chemistry , molecule , physics , quantum mechanics
The photoprocesses of berberine, palmatine, coralyne, sanguinarine, flavopereirine and ellipticine were studied in several solvents. The quantum yields Φ Δ of singlet molecular oxygen formation of berberine, palmatine and sanguinarine are moderate in dichloromethane (0.2–0.6) and much smaller in acetonitrile or trifluoroethanol. For the other alkaloids examined, Φ Δ is rather independent of solvent polarity. The direct and ketone‐sensitized photolysis, using steady‐state irradiation at 313 nm or 248/308 nm laser pulses, was studied by absorption and fluorescence spectroscopy. Thereby, radicals were observed yielding eventually dihydro derivatives as major products, which are thermally back‐converted on admission of oxygen. The quantum yield of conversion of alkaloids to dihydroalkaloids is enhanced in the presence of triethylamine. The reaction in the presence of ketones and electron or H‐atom donors has a quantum yield of close to unity.