C-H Bond Activation: A Versatile Protocol for the Direct Arylation and Alkenylation of Oxazoles

Abstract

The versatile palladium complex Pd(PPh₃)₄ catalyses both direct arylation and alkenylation of oxazoles efficiently. The method is regioselective and stereospecific with respect to bromoalkenes and tolerates a wide range of functional groups.

Key words

oxazole - arylation - alkenylation - palladium - C-H activation

References

• For recent reviews of heteroarenes and arenes by direct arylation, see:
• 1a Alberico D. Scott ME. Lautens M. Chem. Rev.  2007,  107:  174 
• 1b Satoh T. Miura M. Chem. Lett.  2007,  36:  200 
• 1c Seregin IV. Gevorgyan V. Chem. Soc. Rev.  2007,  36:  1173 
• 1d Campeau L.-C. Stuart DR. Fagnou K. Aldrichimica Acta  2007,  40:  35 
• 2 Turner GL. Morris JA. Greaney MF. Angew. Chem. Int. Ed.  2007,  46:  7996 
• 3 Ackermann L. Althammer A. Fenner S. Angew. Chem. Int. Ed.  2008,  48:  201 
• 4a Hachiya H. Hirano K. Satoh T. Miura M. Org. Lett.  2009,  11:  1737 
• 4b Canivet J. Yamaguchi J. Ban I. Itami K. Org. Lett.  2009,  11:  1733 
• 4c During the preparation of our manuscript, Itami published the first example of iridium-catalyzed direct arylation of azoles: Join B. Yamamoto T. Itami K. Angew. Chem. Int. Ed.  2009,  48:  3644 
• For examples of direct arylation of benzoxazole derivatives, see:
• 5a Lewis JC. Wu JY. Bergman RG. Ellman JA. Angew. Chem. Int. Ed.  2006,  45:  1589 
• 5b Bellina F. Calandri C. Cauteruccio S. Rossi R. Tetrahedron  2007,  63:  1970 
• 5c Do H.-Q. Daugulis O. J. Am. Chem. Soc.  2007,  129:  12404 ; and references cited therein
• 5d Ferrer Flegeau E. Popkin ME. Greaney MF. Org. Lett.  2008,  10:  2717 ; and references cited therein
• 5e Yoshizumi T. Satoh T. Hirano K. Matsuo D. Orita A. Otera J. Miura M. Tetrahedron Lett.  2009,  50:  3273 
• 5f Verrier C. Martin T. Hoarau C. Marsais F. J. Org. Chem.  2008,  73:  7383 
• 5g Nandurkar N. Bhanushali M. Malhari B. Bhanage B. Tetrahedron Lett.  2008,  49:  1045 
• 5h For a mechanistic discussion, see: Sanchez RS. Zhuravlev A. J. Am. Chem. Soc.  2007,  129:  5824 
• 5i Derridj F. Djebbar S. Benali-Baitich O. Doucet H. J. Organomet. Chem.  2008,  693:  135 
• 5j Derridj F. Roger J. Geneste F. Djebbar S. Doucet H. J. Organomet. Chem.  2009,  694:  455 
• 5k Ohnmacht SA. Mamone P. Culshaw AJ. Greaney MF. Chem. Commun.  2008,  1241 
• 5l

  See also refs. 3, 4.

• For examples of direct alkenylation of heteroarenes with alkenyl bromides, see:
• 6a Oi S. Aizawa E. Ogino Y. Inoue Y. J. Org. Chem.  2005,  70:  3113 ; and references cited therein
• 6b Zaitsev VG. Daugulis O. J. Am. Chem. Soc.  2005,  127:  4156 
• 6c Gottumukkala AL. Derridj F. Djebbar S. Doucet H. Tetrahedron Lett.  2008,  49:  2926 
• 6d Verrier C. Hoarau C. Marsais F. Org. Biomol. Chem.  2009,  647 
• 6e Koubachi J. El Kazzouli S. Berteina Raboin S. Mouaddib A. Guillaumet G. Synthesis  2008,  2537 
• 7 Palmer DC. Venkatraman S. In Oxazoles: Synthesis, Reactions and Spectroscopy, Part A   Wiley; Hoboken / NJ: 2004. 
• 8 Besselièvre F. Mahuteau-Betzer F. Grierson D. Piguel S. J. Org. Chem.  2008,  73:  3278 
• 9 Besselièvre F. Piguel S. Mahuteau-Betzer F. Grierson D. Org. Lett.  2008,  10:  4029 
• 10a Do H.-Q. Daugulis O. J. Am. Chem. Soc.  2008,  130:  1128 
• 10b Do H.-Q. Kashif Khan RM. Daugulis O. J. Am. Chem. Soc.  2008,  130:  15185 
• 10c Yotphan S. Bergman R. Ellman J. Org. Lett.  2009,  11:  1511 
• 10d See also: Sahnoun S. Messaoudi S. Peyrat JF. Brion JD. Alami M. Tetrahedron Lett.  2008,  49:  7279 
• 11 Cheplogoi P. Mulholland D. Coombes P. Randrianarivelojosia M. Phytochemistry  2008,  69:  1384 
• 12 Unfortunately, these new conditions were not found to be applicable to related azoles such as benzothiazole, benzoxazole or caffeine
• 13 Liégault B. Lapointe D. Caron L. Vlassova A. Fagnou K. J. Org. Chem.  2009,  74:  1826 
• 14 Coulson DR. Inorg. Synth.  1973,  13:  121 
• 15 Nicolaou KC. Hao J. Reddy MV. Rao PB. Rassias G. Snyder SA. Huang X. Chen DY.-K. Brenzovich WE. Giuseppone N. Giannakakou P. O’Brate A. J. Am. Chem. Soc.  2004,  126:  12897 
• 16 Giddens A. Boshoff H. Franzblau S. Barry C. Copp B. Tetrahedron Lett.  2005,  46:  7355 
• 17 Schuh K. Glorius F. Synthesis  2007,  2297 
• 18 Zhang W. Shen G. Zhuang J. Zheng P. Ran X. J. Photochem. Photobiol., A  2002,  147:  25 
• 19 Crowe E. Hossner F. Hughes M.-J. Tetrahedron  1995,  51:  8889 
• 20 Chudasama V. Wilden J. Chem. Commun.  2008,  3768