V. Nair et al. / Tetrahedron Letters 46 (2005) 3217–3219
3219
Table 1 (continued)
Entry
Substrate
Products
CO2Me
Temp (ꢁC)
Yields (%)a
CO2Me
6
7
30
25 = 40(51)b
NHAc
24
25
NHAc
CO2Me
CO2Me
70
70
27 = 30(56)b
26
28
27
NHAc
8
29 = 16
29
a Isolated yeild.
b (Yield) based on recovered starting material.
Prabhakaran, J. Chem. Soc. Rev. 1997, 26, 127; (c) Nair,
V.; Mathew, J. J. Chem. Soc., Perkin Trans. 1 1995,
187.
ments afforded poor yields of products, presumably due
to the easy recombination of the halogen radicals com-
pared to azido radicals. Precedent for the special pro-
pensity of the azido radical for hydrogen atom
abstraction is available in the literature.6
4. Nair, V.; Panicker, S. B.; Nair, L. G.; George, T. G.;
Augustine, A. Synlett (Account) 2003, 156, and references
cited therein.
5. Nair, V.; Rajan, R.; Rath, N. P. Org. Lett. 2002, 4,
127.
6. (a) Baruah, M.; Bols, M. Synlett 2002, 1111; (b) Chen, D.
J.; Chen, Z. C. Tetrahedron Lett. 2000, 41, 7361; (c)
Fontana, F.; Minisci, F.; Yan, Y. M.; Zhao, L. Tetrahe-
dron Lett. 1993, 34, 2517.
Very pertinent to the present work is the Ritter type
reaction of alkyl benzenes using N-hydroxyphthalimide
and CAN reported recently by Ishii and co-workers.11
It is noteworthy that the present method is applicable
to functionalised substrates (Table 1; entries 6 and 7)
and uses reaction conditions that are much milder and
simpler than those reported by Ishii.
7. Nair, V.; Mathew, J. J. Chem. Soc., Perkin Trans. 1 1995,
1881.
8. (a) Welch, W. M.; Kraska, A. R.; Sarges, R.; Koe, B. K. J.
Med. Chem. 1984, 27, 1508; (b) Koe, B. K.; Weismann, A.;
Welch, W. M.; Browne, R. G. J. Pharmacol. Exp. Ther.
1983, 226, 686; (c) Tang, W.; Chi, Y.; Zhang, X. Org. Lett.
2002, 4, 1695.
In conclusion, we have uncovered an experimentally
simple and mechanistically interesting reaction for
C–H oxidation culminating in Ritter amidation. It
appears that the method will be applicable to the
synthesis of a-amino acids and the functionalisation of
a variety of hydrocarbons. Further work is in progress.
9. Typical procedure (Scheme 4): A deoxygenated solution of
CAN (1.26 g, 2.3 mmol) in acetonitrile (15 mL) was added
dropwise to a solution of tetralin (0.132 g, 1 mmol) and
sodium azide (0.098 g,1.5 mmol) in acetonitrile (10 mL)
stirred at 0 ꢁC. Argon, thoroughly deoxygenated by
passing through FieserÕs solution, was continuously bub-
bled through the reaction mixture. It was stirred until the
complete consumption of the starting material was con-
firmed by TLC. The solvent was removed and the residue
diluted with water (15 mL) and extracted with ethyl
acetate (3 · 15 mL). The combined organic extract was
washed with water, brine and dried over anhydrous
sodium sulfate. After removal of the solvent the residue
was subjected to column chromatography on silica gel.
Elution with 70% ethyl acetate–hexane furnished a white
solid 13 (0.147 g, 78%). Mp 148–149 ꢁC (lit. 145–146 ꢁC).
IR (KBr): 3234, 3058, 2913, 1637, 1532, 1439, 1362, 1087,
Acknowledgements
Financial assistance from the Council of Scientific and
is
Industrial Research
acknowledged.
(CSIR),
New
Delhi
References and notes
1. For reviews see: (a) Shilov, A. E.; ShulÕpin, G. B. Chem.
Rev. 1997, 97, 2879; (b) Sen, A. Acc. Chem. Res. 1998, 31,
550.
1
741 cmÀ1. H NMR: d 7.24–7.06 (m, 4H), 5.77 (br s, 1H),
´
5.19–5.13 (m, 1H), 2.79–2.75 (m, 2H), 2.01 (br s, 4H),
1.86–1.82 (m, 3H). 13C NMR: d 168.9, 137.4, 136.7, 129.1,
128.7, 127.2, 126.2, 47.4, 30.1, 29.2, 23.4 and 19.9.
Elemental analysis calculated for C12H15NO: C, 76.16;
H, 7.99; N, 7.40. Found: C, 76.34; H, 8.22; N, 7.52.
2. (a) Barluenga, J.; Bobes, F. G.; Gonzalez, J. M. Angew.
Chem. 2002, 114, 2668; Angew. Chem., Int. Ed. 2002, 41,
2556; (b) Sakaguchi, S.; Nishiwaki, Y.; Kitamura, T.;
Ishii, Y. Angew. Chem. 2001, 113, 228; Angew. Chem., Int.
Ed. 2001, 40, 222; (c) Lee, S.; Fuchs, P. L. Org. Lett. 2004,
6, 1437; (d) Yu, X. Q.; Huang, J. S.; Zhou, X. G.; Che,
C. M. Org. Lett. 2000, 2, 2233.
10. Burk, M. J.; Casy, G.; Johnson, N. B. J. Org. Chem. 1998,
63, 6084.
3. (a) Nair, V.; Balagopal, L.; Rajan, R.; Mathew, J. Acc.
Chem. Res. 2004, 37, 21; (b) Nair, V.; Mathew, J.;
11. Sakaguchi, S.; Hirabayashi, T.; Ishii, Y. Chem. Commun.
2002, 516.