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Photochemical Arylation of Alkenols: Role of Intermediates and Synthetic Significance
Author(s) -
Protti Stefano,
Dondi Daniele,
Fagi Maurizio,
Albini Angelo
Publication year - 2008
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.200701177
Subject(s) - chemistry , anisole , medicinal chemistry , intramolecular force , aryl , diastereomer , photochemistry , solvent , intermolecular force , ether , phenol , organic chemistry , molecule , catalysis , alkyl
A one‐pot, tandem synthesis of cyclic ethers is obtained by addition of photogenerated phenyl cations to hydroxyalkenes. Thus, 2‐ (or 3‐) phenyl‐substituted tetrahydrofurans were prepared by irradiation of 4‐chloro‐ N , N ‐dimethylaniline, ‐anisole, and ‐phenol with β‐hydroxyalkenes and 2‐benzyltetrahydrofurans with γ‐hydroxyalkenes. With nonterminal alkenes [diastereomeric ( E )‐ and ( Z )‐3‐hexen‐1‐ols] trans ‐2‐ethyl‐3‐aryltetrahydrofuran derivatives were stereoselectively formed from both isomers. The output of the photoreaction is structure and solvent dependent and is rationalized through the intermediacy of a phenonium ion from the addition of the primarily formed triplet phenyl cation to the alkenol double bond. Intramolecular addition of the OH group to form benzyl (aryl) tetrahydrofurans is favored inpolar protic solvents, where hydride shifts to form aryltetrahydropyrans also occur, whereas in ethyl acetate, intermolecular addition of the chloride anion to the phenonium ion takes place. The mechanism of the above reactions is also discussed on the basis of computational data.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)