Benzylic Carbon Oxidation by an in situ Formed o-Iodoxybenzoic Acid (IBX) Derivative

Abstract

Benzylic C-H bonds are selectively oxidized to the corresponding carbonyl functionalities using catalytic quantities of 2-iodobenzoic acid (2IBAcid) and Oxone^®. The reported procedure tolerates different functional groups and operates under mild conditions. A radical mechanism is proposed for the transformation and evidence supporting the proposed mechanism is also presented.

oxidation - o-iodoxybenzoic acid (IBX) - single-­electron transfer - rearrangement - Oxone^®

References and Notes

1a Sheldon RA. Kochi JK. Metal-Catalyzed Oxidation of Organic Compounds   Academic; New York: 1981. 

1b Sheldon RA. Kochi JK. Activation and Functionalization of Alkanes   Hill CL. Wiley-Interscience; New York: 1989. 

1c The Activation of Dioxygen and Homogeneous Catalytic Oxidations   Barton DHR. Martell AE. Sawyer DT. Plenum Press; New York: 1993. 

1d Shilov AE. Shulpin GB. Chem. Rev.  1997,  97:  2879 

2a Muzart J. Chem. Rev.  1992,  92:  113 

2b Sasson Y. Zippi GD. Neumann R. J. Org. Chem.  1986,  51:  2880 

2c Yoshino Y. Hayashi Y. Iwahama T. Sakaguchi S. Ishii Y. J. Org. Chem.  1997,  62:  6810 

2d Yamazaki S. Org. Lett.  1999,  1:  2129 

2e Khenkin AM. Neumann R. J. Am. Chem. Soc.  2001,  124:  4198 

2f Catino AJ. Nichols JM. Choi H. Gottipamula S. Doyle MP. Org. Lett.  2005,  7:  5167 

2g Yang D. Wong M.-K. Wang X.-C. Tang Y.-C. J. Am. Chem. Soc.  1998,  120:  6611 

2h Bonvin Y. Callens E. Larrossa I. Henderson D. Oldham J. Burton AJ. Barrett AGM. Org. Lett.  2005,  7:  4549 

2i Lenoir D. Angew. Chem. Int. Ed.  2006,  45:  3206 

3a Nicolaou KC. Montagnon T. Baran PS. Zhong Y.-L. J. Am. Chem. Soc.  2002,  124:  2245 

3b Nicolaou KC. Montagnon T. Baran PS. Angew. Chem. Int. Ed.  2002,  41:  993 

3c Nicolaou KC. Gray DLF. Montagnon T. Harrison SF. Angew. Chem. Int. Ed.  2002,  41:  996 

3d Nicolaou KC. Mathison CJN. Montagnon T.
J. Am. Chem. Soc.  2004,  126:  5182 

3e Kirsch SF. J. Org. Chem.  2005,  70:  10210 

3f Moorthy JN. Singhal N. Senapati K. Tetrahedron Lett.  2006,  47:  1757 

4 Caution! IBX is known to explode upon impact or heating at >200 ˚C, see: Plumb JB. Harper DJ. Chem. Eng. News  1990,  68 (July 16):  3 

5a Thottumkara AP. Vinod TK. Tetrahedron Lett.  2002,  43:  569 

5b Kommareddy A. Bowsher MS. Gunna MR. Botha K. Vinod TK. Tetrahedron Lett.  2008,  49:  4378 

5c Richardson RR. Zayed JM. Altermann S. Smith D. Wirth T. Angew. Chem. Int. Ed.  2007,  46:  6529 

5d Finney JS. Moore NS. Org. Lett.  2002,  4:  3001 

6 Thottumkara AP. Bowsher MS. Vinod TK. Org. Lett.  2005,  7:  2933 

7a Page PCB. Appleby LF. Buckley BR. Allin SM. McKenzie MJ. Synlett  2007,  1565 

7b Richardson RD. Wirth T. Angew. Chem. Int. Ed.  2006,  45:  4402 

8 Kennedy RJ. Stock AM. J. Org. Chem.  1960,  25:  1901 

9 Oxone^® is a 2:1:1 mixture of KHSO₅, KHSO₄, and K₂SO₄. For the use of Oxone^® for the oxidation of 2IBAcid to IBX, see: Frigerio M. Santagostino M. Sputore S. J. Org. Chem.  1999,  64:  4537 

10 Meyer JM. Acc. Chem. Res.  1998,  31:  441 ; and references cited therein

11

We arrived at this compensation by estimating the amount of Oxone^® remaining after heating a solution of Oxone^® in the solvent mixture employed for the reaction for 48 h. We used the Dupont^® reported iodometric procedure for the estimation of Oxone^® available at: http://www.dupont.com/oxone/techinfo/index.html (accessed May 2008).

12a Criegee R. Ber. Dtsch. Chem. Ges. B  1944,  77:  722 

12b Olah GA. Parker DG. Yoneda N. Angew. Chem., Int. Ed. Engl.  1978,  17:  909 

12c Krasutsky PA. Kolomitsyn IV. Krasutsky SG. Kiprof P. Org. Lett.  2004,  6:  2539 

13a Travis BR. Sivakumar M. Hollist O. Borhan B. Org. Lett.  2003,  50:  1031 

13b Gandhari R. Maddukuri PP. Vinod TK. J. Chem. Educ.  2007,  84:  852 

14 Frigerio M. Santagostino M. Tetrahedron Lett.  1994,  35:  8019