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  • Chiral N-alkyl-2,4,6-triphenylpyridiniums as enantioselective triplet photosensitizers. laser flash photolysis and preparative studies.

Chiral N-alkyl-2,4,6-triphenylpyridiniums as enantioselective triplet photosensitizers. laser flash photolysis and preparative studies.

The Journal of organic chemistry (2002-07-20)
Mercedes Alvaro, Pilar Formentín, Hermenegildo García, Emilio Palomares, María J Sabater
ABSTRACT

Three N-alkylpyridinium photosensitizers having chiral alkyl groups have been prepared by reacting 2,4,6-triphenylpyrylium tetrafluoroborate ion with (1R,2S)-(-)-norephedrine, (S)-(+)-2-(aminomethyl)pyrrolidine, and (R)-(-)-1-cyclohexylethylamine. Laser flash photolysis allows detection of the corresponding triplet excited states that are quenched by hydrogen atom donors and electron donors. Asymmetric quenching of the chiral triplet excited state was observed using enantiomerically pure 1,2-diamino cyclohexane as quencher. Low enantiomeric excess values (up to 7%) were measured for the photochemical cyclization of 5-methyl-4-hexenoic acid to its corresponding gamma-lactone using these chiral N-alkylpyridinium as photosensitizers.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
2,4,6-Triphenylpyrylium tetrafluoroborate, 98%