Metal‐Free Cross‐Coupling Reactions of Aryl Sulfonates and Phosphates through Photoheterolysis of Aryl–Oxygen Bonds

Angewandte Chemie International EditionVolume 44, Issue 8 p. 1232-1236 Communication Metal-Free Cross-Coupling Reactions of Aryl Sulfonates and Phosphates through Photoheterolysis of Aryl–Oxygen Bonds† Marco De Carolis, Marco De Carolis Department of Organic Chemistry, University of Pavia, Via Taramelli 10, 27100 Pavia, Italy, Fax: (+39) 0382-507-323Search for more papers by this authorStefano Protti, Stefano Protti Department of Organic Chemistry, University of Pavia, Via Taramelli 10, 27100 Pavia, Italy, Fax: (+39) 0382-507-323Search for more papers by this authorMaurizio Fagnoni Dr., Maurizio Fagnoni Dr. [email protected] Department of Organic Chemistry, University of Pavia, Via Taramelli 10, 27100 Pavia, Italy, Fax: (+39) 0382-507-323Search for more papers by this authorAngelo Albini Prof., Angelo Albini Prof. [email protected] Department of Organic Chemistry, University of Pavia, Via Taramelli 10, 27100 Pavia, Italy, Fax: (+39) 0382-507-323Search for more papers by this author Marco De Carolis, Marco De Carolis Department of Organic Chemistry, University of Pavia, Via Taramelli 10, 27100 Pavia, Italy, Fax: (+39) 0382-507-323Search for more papers by this authorStefano Protti, Stefano Protti Department of Organic Chemistry, University of Pavia, Via Taramelli 10, 27100 Pavia, Italy, Fax: (+39) 0382-507-323Search for more papers by this authorMaurizio Fagnoni Dr., Maurizio Fagnoni Dr. [email protected] Department of Organic Chemistry, University of Pavia, Via Taramelli 10, 27100 Pavia, Italy, Fax: (+39) 0382-507-323Search for more papers by this authorAngelo Albini Prof., Angelo Albini Prof. [email protected] Department of Organic Chemistry, University of Pavia, Via Taramelli 10, 27100 Pavia, Italy, Fax: (+39) 0382-507-323Search for more papers by this author First published: 04 February 2005 https://doi.org/10.1002/anie.200461444Citations: 66 † Partial support of this work by Murst, Rome (Italy) is gratefully acknowledged. Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Graphical Abstract Photochemical cleavage of ArO bonds in phenyl esters substituted with electron-donating groups offers a convenient method for the arylation of alkenes and arenes. The reaction proceeds by an SN1 mechanism via a triplet phenyl cation to form allylbenzene or biphenyl derivatives under mild conditions (see scheme). References 1Z.-Y. Tang, Q.-S. Hu, J. Am. Chem. Soc. 2004, 126, 3058– 3059, and references therein. 2N. Miyaura, A. Suzuki, Chem. Rev. 1995, 95, 2457– 2483; N. Miyaura, Top. Curr. Chem. 2002, 219, 11– 59. 3Very recently, biphenyls were obtained from aromatic ethers either by nickel-catalyzed cross-couplings with aryl Grignard reagents[4] or ruthenium-mediated reactions with aryl boronates.[5] 4J. W. Dankwardt, Angew. Chem. 2004, 116, 2482– 2486; Angew. Chem. Int. Ed. 2004, 43, 2428– 2432. 5F. Kakiuchi, M. Usui, S. Ueno, N. Chatani, S. Murai, J. Am. Chem. Soc. 2004, 126, 2706– 2707, and references therein. 6V. Percec, J.-Y. Bae, D. H. Hill, J. Org. Chem. 1995, 60, 1060– 1065; V. Percec, G. M. Golding, J. Smidrkal, O. Weichold, J. Org. Chem. 2004, 69, 3447– 3452. 7A. H. Roy, J. F. Hartwig, J. Am. Chem. Soc. 2003, 125, 8704– 8705; H. N. Nguyen, X. Huang, S. L. Buchwald, J. Am. Chem. Soc. 2003, 125, 11 818– 11 819; A. Fürstner, A. Leitner, M. Mendez, H. Krause, J. Am. Chem. Soc. 2002, 124, 13 856– 13 863; D. Badone, R. Cecchi, U. Guzzi, J. Org. Chem. 1992, 57, 6321– 6323. 8M. Tanaka, K. Chiba, M. Okita, T. Kaneko, K. Tagami, S. Hibi, Y. Okamoto, H. Shirota, M. Goto, H. Obaishi, H. Sakurai, Y. Machida, I. Yamatsu, J. Med. Chem. 1992, 35, 4665– 4675; T. Hayashi, Y. Katsuro, Y. Okamoto, M. Kumada, Tetrahedron Lett. 1981, 22, 4449– 4452. 9In contrast to the singlet states, triplet phenyl cations behave as selective electrophiles and react with π, not n nucleophiles; see reference [10]. 10S. Milanesi, M. Fagnoni, A. Albini, Chem. Commun. 2003, 216– 217. 11B. Guizzardi, M. Mella, M. Fagnoni, M. Freccero, A. Albini, J. Org. Chem. 2001, 66, 6353– 6363; M. Mella, P. Coppo, B. Guizzardi, M. Fagnoni, M. Freccero, A. Albini, J. Org. Chem. 2001, 66, 6344– 6352; B. Guizzardi, M. Mella, M. Fagnoni, A. Albini, Tetrahedron 2000, 56, 9383– 9389; B. Guizzardi, M. Mella, M. Fagnoni, A. Albini, Chem. Eur. J. 2003, 9, 1549– 1555; A. Fraboni, M. Fagnoni, A. Albini, J. Org. Chem. 2003, 68, 4886– 4893. 12S. Protti, M. Fagnoni, M. Mella, A. Albini, J. Org. Chem. 2004, 69, 3465– 3473. 13J. W. Meyer, G. S. Hammond, J. Am. Chem. Soc. 1972, 94, 2219– 2228; M. R. Sandner, E. Hedaya, D. J. Trecker, J. Am. Chem. Soc. 1968, 90, 7249– 7254. 14D. Bellus in Advances in Photochemistry, Vol. 8 (Eds.: ), Wiley-Interscience, New York, 1971, pp. 109– 159; J. L. Stratenus, E. Havinga, Recl. Trav. Chim. Pays-Bas 1966, 85, 434– 436; E. Elhalem, B. N. Bailey, R. Docampo, I. Ujvari, S. H. Szajnman, J. B. Rodriguez, J. Med. Chem. 2002, 45, 3984– 3999. 15aY.-S. Chang, J.-S. Jang, M. L. Deinzer, Tetrahedron 1990, 46, 4161– 4164; 15bQ.-Y. Chen, Z.-T. Li, J. Org. Chem. 1993, 58, 2599– 2604; 15cS. Knapp, J. Albaneze, H. J. Schugar, J. Org. Chem. 1993, 58, 997– 998. 16E. Havinga, R. O. De Jongh, W. Dorst, Recl. Trav. Chim. Pays-Bas 1956, 75, 378– 383. 17R. S. Givens, L. W. Kueper III, Chem. Rev. 1993, 93, 55– 66. 18aM. Nakamura, Y. Okamoto, S. Takamuku, Chem. Commun. 1996, 209– 210; 18bM. Shi, K. Yamamoto, Y. Okamoto, S. Takamuku, Phosphorus Sulfur Silicon Relat. Elem. 1991, 60, 1– 14; 18cM. Nakamura, A. Ouchi, M. Miki, T. Majima, Tetrahedron Lett. 2001, 42, 7447– 7449. 19Palladium-catalyzed arylation of allyltrimethylsilane starting from aryl iodides led to allyl aromatic compounds in low to good selectivities according to the conditions used,[20] whereas aryl triflates afforded arylated allylsilanes.[21] 20T. Jeffery, Tetrahedron Lett. 2000, 41, 8445– 8449. 21K. Olofsson, M. Larhed, A. Hallberg, J. Org. Chem. 1998, 63, 5076– 5079. 22Methoxyphenyl esters exhibited the long-wavelength band at 275–280 nm, with virtually no absorption at 310 nm, thus poorly matching the spectrum of the lamp (see Experimental Section). In contrast, aminophyenyl esters strongly absorbed at 310 nm (ε≈1200–2500 mol−1 dm3 cm−1). 23Some irradiations with mesylate 5 in the presence of ATMS were carried out under nonsensitized conditions at 254 nm and gave the same product distribution, although product 13 was not stable under prolonged irradiation. The use of the lamps at a wavelength of 310 nm prevented both product photodegradation and competititve absorption by benzene when this was used as the trap. A possible wavelength dependence of the reaction is under investigation. 24In these acetone-sensitized reactions in the presence of ATMS, the Paternò-Büchi oxetane was found as a by-product in a variable amount, particularly in the case of phosphate 8. 25The presence of a protic polar medium (for example, water) could dramatically favor the photoheterolytic process, see: M. Freccero, M. Fagnoni, A. Albini, J. Am. Chem. Soc. 2003, 125, 13 182– 13 190. 264-Methoxybiphenyl was obtained only in 7 % yield in aprotic solvent after irradiation of 4-chloroanisole in the presence of benzene (1 m). In TFE the yield did not exceed 70 %. 27Triethylamine (0.05 m) buffers the acid liberated in the photolysis of the esters and avoids degradation and polymerization of the photoproducts, as indicated by experiments using cesium carbonate instead which led to the same product distribution. However, the use of the MeCN/water mixed solvent made the use of a base unnecessary, thus supporting the idea that electron transfer between the amine and the triplet state of the aromatic reagents (very short lived in the halides, reference [25] and presumably also of the esters) is not involved in the arylation reaction. 28Attack of allyltrimethylsilane by cations is well known. The alternative formation of compounds 9 and 13 by a photogenerated aryl radical is excluded on two grounds. First, it has been reported that such a path operates only with strongly electrophilic aryl radicals (for example, 3,5-dinitrophenylradical[29]) and, then, only with a poor yield. Moreover, β fragmentation of the adduct radical leading to allylated derivatives is usually observed with an (Me3Si)3Si group rather than with other alkyl- or aryl-substituted silanes.[30] Second, purposely designed experiments disfavor this hypothesis. Thus, generation of an authentic 4-methoxyphenyl radical by photolysis of 4-bromoanisole in the presence of ATMS gave no allylated compounds but only anisole. Likewise, substituting 2,3-dimethylbutene for ATMS gave 2,3-dimethyl-3-(4-methoxyphenyl)-1-butene, 2,3-dimethyl-3-(4-methoxyphenyl)-2-(2,2,2-trifluoroethoxy)butane, 2,3-dimethyl-2-(4-methoxyphenyl)butane, and 2-(4-methoxyphenyl)-2-(2,2,2-trifluoroethoxy)-3,3-dimethylbutane from 5 in CF3CH2OH/Cs2CO3, in the same proportion as from 4-chloroanisole (see reference [12]). This reaction is difficult to envisage other than involving loss of a proton from (or solvent addition to) an adduct cation. (Further evidence is the fact that a cationic Wagner–Meerwein rearrangement has taken place in the last product). 29F. Ek, L.-G. Wistrand, T. Frejd, J. Org. Chem. 2003, 68, 1911– 1918. 30L. Chabaud, P. James, Y. Landais, Eur. J. Org. Chem. 2004, 3173– 3199. 31The role of solvents, and in particular of alcohols, as hydrogen donors (and not as n nucleophiles) in the reaction with the triplet phenyl cation has been previously demonstrated, see Refs. [10–12]. 32In rare instances, the Suzuki coupling occurred under microwave irradiation in the absence of a catalyst, see: N. E. Leadbeater, M. Marco, Angew. Chem. 2003, 115, 1445– 1447; Angew. Chem. Int. Ed. 2003, 42, 1407– 1409. 33Quartz allowed the absorption of all of the light emitted by the lamp. Citing Literature Supporting Information Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2005/z461444_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article. Volume44, Issue8February 11, 2005Pages 1232-1236 ReferencesRelatedInformation