stereoselective addition to the two double bonds, and two kinds
of reaction pathways of 2,3-allenoates have been disclosed for
reactions with electrophiles so far: (1) selective addition to the
â,γ-double bond to give stereodefined functionalized vinyl
compounds (type a, Scheme 1);6,7d (2) interaction of 2,3-
allenoates with electrophiles followed by participation of the
ester carbonyl group to form cyclic cations. Further reaction
with nucleophiles yields unstable cyclic intermediates which
evolve to the final products (type b, Scheme 1). As for the
reaction pathway type b, most cases give γ-butenolides as the
products of electrophilic cyclization in the presence of water,7
and scarcely any other nucleophile has been reported.
Reaction of 2,3-Allenoates with TsNBr2 in the
Presence of Base: A Facile Highly Stereoselective
Synthesis of
(1E,2E)-3-Bromo-4-oxo-N′-tosyl-2-alkenoxylimidic
Acid Ethyl Esters
Ruwei Shen† and Xian Huang*,†,‡
Department of Chemistry, Zhejiang UniVersity (Xixi Campus),
Hangzhou 310028, People’s Republic of China, and State Key
Laboratory of Organometallic Chemistry, Shanghai Institute of
Organic Chemistry, Chinese Academy of Sciences,
Shanghai 200032, People’s Republic of China
The utility of N,N-dibromo-p-toluenesulfonamide (TsNBr2)
as a Br+ source has attracted our interest recently because of
its simplicity and efficiency.8 This reagent could provide a
sulfonamide as the nucleophilic counterpart to construct a
carbon-nitrogen bond, thus serving as a good aminobromination
reagent in organic synthesis.9 Although much work has been
done in aminobromination, hydrobromination, and alkoxybro-
mination of the CdC unsaturated bond using TsNBr2 in the
past,9,10 the interaction with allenes has not been studied and
ReceiVed February 5, 2007
(3) For recent examples, see: (a) Ohno, H.; Miyamura, K.; Mizutani,
T.; Kadoh, Y.; Takeoka, Y.; Hamaguchi, H.; Tanaka, T. Chem.sEur. J.
2005, 11, 3728. (b) Wender, P. A.; Croatt, M. P.; Deschamps, N. M. Angew.
Chem., Int. Ed. 2006, 45, 2459. (c) Brummond, K. M.; Gao, D. Org. Lett.
2003, 5, 3491. (d) Mukai, C.; Takahashi, Y. Y. Org. Lett. 2005, 7, 5793.
(e) Ma, S.; Jiao, N.; Zheng, Z.; Ma, Z.; Lu, Z.; Ye, L.; Deng, Y.; Chen, G.
Org. Lett. 2004, 6, 2193. (f) Hamaguchi, H. S.; Kosaka; Ohno, H.; Tanaka,
T. Angew. Chem., Int. Ed. 2005, 44, 1513. (g) Zhu, G.; Zhang, Z. Org.
Lett. 2004, 6, 4041. (h) Inagaki, F.; Mukai, C. Org. Lett. 2006, 8, 1217. (i)
Kuroda, N.; Takahashi, Y.; Yoshinaga, K.; Mukai, C. Org. Lett. 2006, 8,
1843. (j) Ohno, H.; Takeoka, Y.; Miyamura, K.; Kadoh, Y.; Tanaka, T.
Org. Lett. 2003, 5, 4763. (k) Feldman, K. S.; Iyer, M. R. J. Am. Chem.
Soc. 2005, 127, 4590. (l) Ma, S.; Gu, Z. J. Am. Chem. Soc. 2005, 127,
6182. (m) Parthasarathy, K.; Jeganmohan, M.; Cheng, C.-H. J. Am. Chem.
Soc. 2006, 128, 621.
(4) (a) Ma, S.; Ren, H.; Wei, Q. J. Am. Chem. Soc. 2003, 125, 4817. (b)
Ma, S.; Wei, Q. Eur. J. Org. Chem. 2000, 1, 1939. (c) Ma, S.; Wei, Q.;
Wang, H. Org. Lett. 2000, 2, 3893. (d) Ma, S.; Li, L. Synlett 2001, 1, 1206
and refs therein.
(5) For recent examples, see: (a) Zhu, X. F.; Schaffner, A. P.; Li, R. C.;
Kwon, O. Org. Lett. 2005, 7, 2977. (b) Dieter, R. K.; Lu, K.; Velu, S. E.
J. Org. Chem. 2000, 65, 8715. (c) Chakravarty, M.; Kumara Swamy, K. C.
J. Org. Chem. 2006, 71, 9128. (d) Hopkins, C. D.; Guan, L.; Malinakova,
H. C. J. Org. Chem. 2005, 70, 6848. (e) Lambert, T. H.; Macmillan, D. W.
J. Am. Chem. Soc. 2002, 124, 13646. (f) Lu, C.; Lu, X. Org. Lett. 2002, 4,
4677. (g) Lu, X.; Zhang, C.; Xu, Z. Acc. Chem. Res. 2001, 34, 535. (h)
Yoshino, T.; Ng, F.; Danishefsky, S. J. J. Am. Chem. Soc. 2006, 128, 14185.
(i) Jung, M. E.; Murakami, M. Org. Lett. 2006, 8, 5857.
A novel reaction pathway of 2,3-allenoates with an electro-
phile (TsNBr2) in the presence of K2CO3 to produce (1E,2E)-
3-bromo-4-oxo-N′-tosyl-2-alkenoxylimidic acid ethyl esters
is reported. The reaction proceeds in a highly stereoselective
fashion. A plausible mechanism to rationalize this reaction
is also proposed.
Allenes, featured by the presence of two orthogonal π-bonds,
show unique reactivity in organic synthesis.1 In the past decades,
much attention has been paid to the study of their reactivity,
especially on the control of the relative selectivity and their
potential synthetic utilities.2-5 Researchers have found that both
regioselective and stereoselective addition to allenes can be
tuned by introducing various nucleophilic functionalities at the
R-carbon atom.4 Recently, 2,3-allenoates, a readily accessible
class of allenes, have exhibited great potential in the synthesis
of many compounds with biological and synthetic importance.5
Generally, the attached ester groups facilitate the regio- and
(6) Chen, G.; Fu, C.; Ma, S. J. Org. Chem. 2006, 71, 9877.
(7) (a) Hanessian, S. The Total Synthesis of Natural Products: The Chiron
Approach; Pergamon Press: New York, 1983; Chapter 9. (b) de March,
P.; Font, J.; Gracia, A.; Zheng, Q. J. Org. Chem. 1995, 60, 1814. (c) Fu,
C.; Ma, S. Eur. J. Org. Chem. 2005, 3942. (d) Chen, G.; Fu, C.; Ma, S.
Tetrahedron 2006, 62, 4444. (e) Ma, S.; Wu, S. Tetrahedron Lett. 2001,
42, 4075. (f) Marshall, J. A.; Bartley, G. S.; Wallace, E. M. J. Org. Chem.
1996, 61, 5729.
(8) For preparation of TsNBr2, see: (a) Nair, C. G. R.; Indrasen, P.
Talanta 1976, 23, 239. (b) Tajbakhsh, M.; Khazaei, A.; Mahalli, M. S.;
Vaghi, R. G. Phosphorus, Sulfur Silicon Relat. Elem. 2004, 179, 1159-
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(9) (a) Kharasch, M. S.; Priestley, H. N. J. Am. Chem. Soc. 1939, 61,
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Pharm. Bull. 1977, 25, 556. (c) Hegedus, L. S.; McKearin, J. M. J. Am.
Chem. Soc. 1982, 104, 2444. (d) Revesz, L.; Blum, E.; Wicki, R.
Tetrahedron Lett. 2005, 46, 5577. (e) Griffith, D. A.; Danishefsky, S. J. J.
Am. Chem. Soc. 1996, 118, 9526.
† Zhejiang University.
‡ Chinese Academy of Sciences.
(1) (a) Patai, S. The Chemistry of Ketenes, Allenes, and Related
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H. F.; Coppola, G. M. Allenes in Organic Synthesis; John Wiley & Sons:
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(2) (a) Smadja, W. Chem. ReV. 1983, 83, 263. (b) Marshall, J. A. Chem.
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10.1021/jo070239z CCC: $37.00 © 2007 American Chemical Society
Published on Web 04/13/2007
J. Org. Chem. 2007, 72, 3961-3964
3961