Copper(II)-Catalyzed Oxidative Esterification of Substituted p-Cresols under Ligand- and Additive-Free Conditions

Abstract

A facile, atom-economical, and efficient Cu(OAc)₂-catalyzed oxidative esterification of substituted p-cresols was developed with ambient air as the terminal oxidant. This ligand- and additive-free esterification protocol allows an environmentally benign and reagent-economical access to benzyl esters.

Key words

copper catalysis - esterification - substituted p-cresols - ambient air - sustainable reaction

• References and Notes

• 1a Handbook of C–H Transformations. Vol. 1 and 2. Dyker G. Wiley-VCH; Weinheim: 2005
• 1b Yu J.-Q, Shi Z In Topics in Current Chemistry . Vol. 292. Springer; Berlin: 2010

For selective reviews on C–C bond formation via C–H activation, see:
• 2a Kakiuchi F, Kochi T. Synthesis 2008; 3013
• 2b Ritleng V, Sirlin C, Pfeffer M. Chem. Rev. 2002; 102: 173
• 2c Alberico D, Scott ME, Lautens M. Chem. Rev. 2007; 107: 174
• 2d Ackemann L, Chen X, Engle KM, Wang D.-H, Yu J.-Q. Angew. Chem. Int. Ed. 2009; 48: 5094
• 2e Kulkarni AA, Daugulis O. Synthesis 2009; 4087

For selective reviews on C–X bond formation via C–H activation, see:
• 3a Dick AR, Sanford MS. Tetrahedron 2006; 62: 2439

C–O bond formation:
• 3b Alonso DA, Najera C, Pastor IM, Yus M. Chem. Eur. J. 2010; 16: 5274

C–N bond formation:
• 3c Collet F, Dodd RH, Dauban P. Chem. Commun. 2009; 5061

C–B bond formation:
• 3d Mkhalid IA, Barnard JH, Marder TB, Murphy JM, Hartwig JF. Chem. Rev. 2010; 110: 890
• 4 Yoneyama T, Crabtree RH. J. Mol. Catal. A 1996; 108: 35
• 5 Shoji M, Uno T, Kakeya H, Onose R, Shiina I, Osada H, Hayashi Y. J. Org. Chem. 2005; 70: 9905
• 6 Mitsudome T, Umetani T, Nosaka N, Mori K, Mizugaki T, Ebitani K, Kaneda K. Angew. Chem. Int. Ed. 2006; 45: 481
• 7a Do H.-Q, Daugulis O. J. Am. Chem. Soc. 2007; 129: 12404
• 7b Li Z, Bohle DS, Li C.-J. Proc. Natl. Acad. Sci. U.S.A. 2006; 103: 8928
• 7c Uemura T, Imoto S, Chatani N. Chem. Lett. 2006; 35: 842
• 7d Li Z, Li C.-J. J. Am. Chem. Soc. 2005; 127: 6968
• 7e Do H.-Q, Daugulis O. J. Am. Chem. Soc. 2008; 130: 1128
• 8 Chen X, Hao X.-S, Goodhue CE, Yu J.-Q. J. Am. Chem. Soc. 2006; 128: 6790
• 9 Wang W.-H, Luo F, Zhang S.-H, Cheng J. J. Org. Chem. 2010; 75: 2415
• 10a Jiang J.-A, Du J.-L, Liao D.-H, Wang Z.-G, Ji Y.-F. Tetrahedron Lett. 2014; 55: 1406
• 10b Jiang J.-A, Chen C, Huang J.-G, Liu H.-W, Cao S, Ji Y.-F. Green Chem. 2014; 16: 1248
• 10c Jiang J.-A, Du J.-L, Wang Z.-G, Zhang Z.-N, Xu X, Zheng G.-L, Ji Y.-F. Tetrahedron Lett. 2014; 55: 1677
• 11 Itoh T, Nakanishi E, Okayama M, Kubo M. Macromolecules 2000; 33: 269
• 12 Boldron C, Gamez P, Tooke DM, Spek AL, Reedijk J. Angew. Chem. Int. Ed. 2005; 44: 3585
• 13 Boldron C, Gamez P, Tooke DM, Spek AL, Reedijk J. Dalton Trans. 2005; 3535

For efficient recycling of Cu(OAc)₂ by ambient air or O₂, see:
• 14a John A, Nicholas KM. J. Org. Chem. 2011; 76: 4158
• 14b Sherman ES, Chemler SR, Boon Tan T, Gerlits O. Org. Lett. 2004; 6: 1573
• 14c Klein JE. M. N, Perry A, Taylor RJ. K. Org. Lett. 2010; 12: 3446
• 14d Antilla JC, Buchwald SL. Org. Lett. 2001; 3: 2077
• 14e Zhang L, Ang GY, Chiba S. Org. Lett. 2011; 13: 1622
• 15 Baik W, Lee HJ, Jang JM, Koo S, Kim BH. J. Org. Chem. 2000; 65: 108
• 16 Bozell JJ, Hames BR. J. Org. Chem. 1995; 60: 2398
• 17 General Procedure for the Synthesis of 3a A mixture of substrate 1a (1.0 mmol), benzoic acid (2a, 1.0 mmol), and Cu(OAc)₂ (10 mol%) in MeCN (4.0 mL) was stirred under ambient air at 75 °C for 13 h. The reaction mixture was concentrated in vacuo to give a residue, to which were added HCl (10 mL, 2%) and EtOAc (15 mL). The organic phase was separated, and the aqueous phase was further extracted with EtOAc (5 mL, twice). The combined organic layers were washed with sat. aq NaHCO₃ (20 mL) and brine (20 mL). The EtOAc was dried over anhydrous Na₂SO₄ and concentrated in vacuo to give a residue, which was purified by column chromatography on silica gel (eluents: PE–EtOAc, 30:1) to provide the corresponding product 3a. Characterization for 3a Yellow solid, mp 60–63 °C, 0.20 g (79%). ¹H NMR (400 MHz, CDCl₃): δ = 2.26 (s, 6 H), 4.67 (br s, 1 H), 5.23 (s, 2 H), 7.08 (s, 2 H), 7.42 (t, J = 8.0 Hz, 2 H), 7.55 (t, J = 8.0 Hz, 1 H), 8.06 (d, J = 8.0 Hz, 2 H) ppm. ¹³C NMR (100 MHz, CDCl₃): δ = 16.0 (2 C), 66.9, 123.2 (2 C), 128.4 (2 C), 128.5, 129.3 (2 C), 129.7 (2 C), 130.2, 133.0, 152.4, 166.7 ppm. HRMS (EI): m/z [M⁺] calcd for C₁₆H₁₆O₃: 256.1099; found: 256.1100