Abstract
We report that ethylbenzenes can be directly oxidized to the
corresponding α-keto esters with molecular oxygen in the
presence of 48% aqueous HBr under visible light irradiation.
This synthetic procedure is the first example for direct preparation
of the corresponding α-keto esters from ethylbenzenes.
Key words
photooxidation - HBr - aerobic - ethylbenzene - α-keto ester
References and Notes
1a
Comprehensive Organic Transformations
2nd
ed.:
Larock RC.
Wiley;
New
York:
1999.
p.1625
1b
March’s
Advanced Organic Chemistry
6th ed.:
Smith MB.
March JA.
John
Wiley & Sons, Inc.;
Hoboken:
2007.
p.1745
1c
Uyanik M.
Fukatsu R.
Ishihara K.
Chem. Asian
J.
2010,
5:
456
2a
Kraus GA.
Zhang N.
J.
Org. Chem.
2000,
65:
5644
2b
Akiyama T.
Suzuki M.
Chem. Commun.
1997,
2357
3a
Loupy A.
Monteux DA.
Tetrahedron
2002,
58:
1541
3b
Tanaka K.
Katsurada M.
Ohno F.
Shiga Y.
Oda M.
J.
Org. Chem.
2000,
65:
432
3c
Axten JM.
Krim L.
Kung HF.
Winkler JD.
J.
Org. Chem.
1998,
63:
9628
4a
Xiang J.
Ming L.
Bao L.
Chin. Chem. Lett.
2009,
20:
55
4b
Lee JI.
J.
Korean Chem. Soc.
2004,
48:
103
4c
Maeda H.
Hino N.
Yamauchi Y.
Ohmori H.
Chem. Pharm. Bull.
2000,
48:
1196
4d
Kashima C.
Shirahata Y.
Tsukamoto Y.
Heterocycles
1998,
49:
459
4e
Rambaud M.
Bakasse M.
Duguay G.
Villieras J.
Synthesis
1988,
564
4f
Creary X.
J.
Org. Chem.
1987,
52:
5026
4g
Itoh O.
Nagata T.
Nomura I.
Takanaga T.
Sugita T.
Ichikawa K.
Bull. Chem. Soc. Jpn.
1984,
57:
810
4h
Weinstock LM.
Currie RB.
Lovell AV.
Synth. Commun.
1981,
11:
943
4i
Nimitz JS.
Mosher
HS.
J.
Org. Chem.
1981,
46:
211
5a
Tatlock JH.
J. Org. Chem.
1995,
60:
6221
5b
Müller P.
Godoy J.
Tetrahedron
Lett.
1982,
23:
3661
6a
Li L.-S.
Wu Y.-L.
Tetrahedron
Lett.
2002,
43:
2427
6b
Nishinaga A.
Maruyama K.
Yoda K.
Okamoto H.
J. Chem. Soc., Chem.
Commun.
1990,
876
For recent examples, see:
7a
Johnston EV.
Karlsson EA.
Tran L.-H.
Aakermark B.
Baeckvall J.-E.
Eur. J. Org. Chem.
2010,
1971
7b
Yadav GD.
Motirale BG.
Chem. Eng.
J.
2010,
156:
328
7c
Park HJ.
Lee JC.
Synlett
2009,
79
7d
Hosseinzadeh R.
Tajbakhsh M.
Khaledi H.
J.
Chin. Chem. Soc.
2008,
55:
239
7e
Oba M.
Okada Y.
Nishiyama K.
Shimada S.
Ando W.
Chem.
Commun.
2008,
5378
7f
Shei C.-T.
Chien H.-L.
Sung K.
Synlett
2008,
1021
7g
Pandey SK.
Bisai A.
Singh VK.
Synth. Commun.
2007,
37:
4099
7h
Demizu Y.
Shiigi H.
Oda T.
Matsumura Y.
Onomura O.
Tetrahedron
Lett.
2007,
49:
48
7i
Lu N.
Lin Y.-C.
Tetrahedron Lett.
2007,
48:
8823
8a
Wu X.
Gorden AEV.
Eur.
J. Org. Chem.
2009,
503
8b
Nakanishi M.
Bolm C.
Adv. Synth. Catal.
2007,
349:
861
8c
Golchoubian H.
Ghaziani ANK.
Pol. J.
Chem.
2005,
79:
825
8d
Das S.
Bhowmick T.
Punniyamurthy T.
Dey D.
NaTh J.
Chaudhuri MK.
Tetrahedron Lett.
2003,
44:
4915
8e
Wentzei BB.
Donners MPJ.
Alster PL.
Feiters MC.
Nolte RJM.
Tetrahedron
2000,
56:
7797
8f
Matsunaka K.
Iwahama T.
Sakaguchi S.
Ishii Y.
Tetrahedron Lett.
1999,
40:
2165
8g
Zhao D.
Lee DG.
Synthesis
1994,
915
8h
Choudary BM.
Reddy GVS.
Rao KK.
J. Chem. Soc., Chem.
Commun.
1993,
323
8i
Wasserman HH.
Ives JL.
J.
Org. Chem.
1985,
50:
3573
9a
Kobayashi T.
Yamashita H.
Sakakura T.
Tanaka M.
J.
Mol. Catal.
1987,
41:
379
9b
Sakakura T.
Yamashita H.
Kobayashi T.
Hayashi T.
Tanaka M.
J.
Org. Chem.
1987,
52:
5733
9c
Tanaka M.
Kobayashi T.
Sakakura T.
J.
Chem. Soc., Chem. Commun.
1985,
837
9d
Ozawa F.
Kawasaki N.
Yamamoto T.
Yamamoto A.
Chem. Lett.
1985,
14:
567
9e
Tanaka M.
Kobayashi T.
Sakakura T.
Itatani H.
Danno S.
Zushi K.
J. Mol. Catal.
1985,
32:
115
10
Schaefer JP.
Corey EJ.
J. Org. Chem.
1959,
24:
1825
11
Zhuang J.
Wang C.
Xie F.
Zhang W.
Tetrahedron
2009,
65:
9797
12a
Izawa Y.
Ishiguro K.
Tomioka H.
Bull. Chem. Soc. Jpn.
1983,
56:
1490
12b
Izawa Y.
Tomioka H.
Natsume M.
Beppu S.
Tsujii H.
J.
Org. Chem.
1980,
45:
4835
13a
Hirashima S.
Nobuta T.
Tada N.
Miura T.
Itoh A.
Org. Lett.
2010,
12:
1620
13b
Hirashima S.
Itoh A.
J. Synth. Org. Chem. Jpn.
2008,
66:
748
13c
Hirashima S.
Itoh A.
Photochem. Photobiol. Sci.
2007,
6:
521
13d
Sugai T.
Itoh A.
Tetrahedron Lett.
2007,
48:
9096
13e
Hirashima S.
Itoh A.
Synthesis
2006,
1757
13f
Itoh A.
Hashimoto S.
Kodama T.
Masaki Y.
Synlett
2005,
2107
13g
Itoh A.
Kodama S.
Hashimoto S.
Masaki Y.
Synthesis
2003,
2289
14
Tada N.
Ban K.
Hirashima S.
Miura T.
Itoh A.
Org. Biomol.
Chem.
2010,
8:
4701
15 When 48% aq HBr (1.2 equiv)
and H2O (100 µL) were used as additive, ethylbenzene 1d was converted into α-bromo-acetophenone
(3d) in 68% yield.¹4
16
Typical Procedure:
An anhyd EtOAc solution (5 mL) of ethylbenzenes (0.3 mmol) and 48% aq
HBr (0.75 mmol) in a pyrex test tube equipped with an O2 balloon
was stirred and irradiated with four 22-W fluorescent lamps, which
were set up at a distance of 65 mm, for 20 h. The temperature of
the final stage of this reaction was about 40 ˚C. The reaction mixture
was concentrated under reduced pressure, and the pure product was
obtained by purification with preparative TLC.
