3594-97-6Relevant academic research and scientific papers
Photochemistry of Phenoxybenzyl Alcohols in Aqueous Solution: Photosolvolysis vs Photorearrangement to 6H-Dibenzopyrans
Huang, C.-G.,Wan, Peter
, p. 4846 - 4853 (2007/10/02)
The photochemistry of three phenoxybenzyl alcohols (1-3) has been studied in MeOH, CH3CN, and in aqueous solution.It was found that both of the ortho-substituted phenoxybenzyl alcohols 1 and 2 gave the corresponding 6H-dibenzopyrans 6 and 10, via a mechanism believed to involve initial aryl C-O bond homolysis followed by rearrangement to give a 2-(2'-hydroxyphenyl)benzyl alcohol (biphenyl) derivative, which subsequently undergoes a photocyclization reaction to the corresponding 6H-dibenzopyran.The quantum yield for formation of 6 (from 1) was 0.0073 in neutral 6:4 H2O-CH3CN.Lower quantum yields for formation of 6 were observed on photolysis in pure organic solvents (Φ = 0.0015 in 100percent CH3CN).The meta-substituted isomer 3 did not give any reaction via a similar photocyclization process: its photochemistry involves initial aryl C-O bond homolysis followed by simple radical recoupling to give isomeric hydroxybiphenyls, as well as products derived from radical escape.In aqueous sulfuric acid solution (pH 2), a competing acid-catalyzed photosolvolysis reaction was observed for all of these compounds (i.e., C-OH bond heterolysis with assistance of hydronium ion); it was the only observed reaction in moderately concentrated sulfuric acid solution.
Mechanism of Photoisomerization of Xanthene to 6H-Dibenzopyran in Aqueous Solution
Huang, C.-G.,Shukla, Deepak,Wan, Peter
, p. 5437 - 5442 (2007/10/02)
A new photoreaction, the photoisomerization of xanthene (1) to 6H-dibenzopyran (2) (ca. 70percent) (Φ = 0.0035 in 7:3 H2O-CH3CN) in aqueous CH3CN solution is reported.In addition to 2, 2-benzylphenol (3) (Φ ca. 0.001), 9,9'-bixanthyl (4) (Φ 1, to generate a singlet biradical.Trivial recombination gives back unreacted 1.Hydrogen abstraction from solvent leads to the photoreduction product 3.However, recombination of the biradical at the ipso benzylic position (ortho to phenol) gives a cyclohexadienone intermediate 17.Subsequent transformation of this species to 2 occurs via an o-quinone methide intermediate 18, which itself can be trapped with MeOH or H2O, to give the corresponding methyl ether derivative 8 or alcohol 5.
