Psoralen-olefin photoproducts: first observation of a photo-ene reaction.
Methyl-substituted psoralens (4'-(hydroxymethyl)-4,5',8-trimethylpsoralen and 4,5',8-trimethylpsoralen) are found to yield an ene product as well as the expected [2 + 2] cycloaddition product from photochemical reaction with simple olefins. As determined by absorbance, liquid chromatography-mass spectrometry and nuclear magnetic resonance, both products are formed at the pyrone side of the respective psoralen. The product distribution is dependent on olefin concentration as well as the nature of the olefin. In deoxygenated solutions, cyclic olefins form as much as 50% ene product, while unsubstituted straight-chain olefins form as little as 3%. In oxygenated solutions, the product distribution is strongly affected by singlet oxygen.
University of Colorado, Department of Chemistry and Biochemistry, Boulder 80309.
D J
DJ
Semin
P C
PC
Winkler
K L
KL
Rowlen
D000475:Alkenes / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D015394:Molecular Structure; D010782:Photolysis; D013056:Spectrophotometry, Ultraviolet; D014307:Trioxsalen / Q000031:analogs & derivatives* / Q000737:chemistry*
D000475:Alkenes; C016507:hydroxymethyltrioxsalen; D014307:Trioxsalen