M. Maddani, K. R. Prabhu / Tetrahedron Letters 48 (2007) 7151–7154
7153
References and notes
NH
2 4
S
2h
S
N
H
1. (a) Kuhn, F. E.; Santos, A. M.; Abrantes, M. Chem. Rev.
¨
5
2006, 106, 2455; (b) Schrock, R. R. J. Mol. Catal., A:
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Luck, R. L.; Wang, Z.; Mu, Z.; Evans, D. G.; Duan, X.
Inorg. Chim. Acta 2004, 357, 3223.
MoO2(S2CNMe2)2
HO
H
1b
6
NH2
N
S
1.5h
O
7
Scheme 2.
2. (a) Enemark, J. H.; Cooney, J. J. A.; Wang, J. J.; Holm, R.
H. Chem. Rev. 2004, 104, 1175; (b) Wilson, G. L.;
Greenwood, R. J.; Pilbrow, J. R.; Spence, J. T.; Wedd,
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2c produced the corresponding thiourea 3c in good
yield (70%, 50 min). Cyclohexylamine (2d) and n-hexyl-
amine (2e) furnished the corresponding thioureas 3d
and 3e17 in 66% and 85% yields, respectively. Thiourea
derivatives of amino acids are important as they can
be used as organocatalysts.11 Therefore, we subjected
the methyl esters of L-phenylalanine, L-tyrosine, and
L-leucine (2f, 2g, and 2h, respectively) to similar reac-
tions with 1a. The corresponding thiourea derivatives
3f, 3g, and 3h were formed in moderate yields (51–
58%). Similarly, Mo–xanthate 1b, the methyl analogue
of reagent 1a, also produced similar results. Exam-
ples are provided in Table 2. Benzylamine, cyclohexyl-
amine, and the methyl ester of L-phenylalanine (2a,
2d, and 2g) produced thioureas 3i, 3j, and 3k,17 respec-
tively, in moderate yields (62%, 54%, and 51%) on reac-
tion with 1b. However, reaction of p-bromoaniline or
triethylamine with reagent 1a or 1b failed to furnish
the corresponding thioureas under similar reaction
conditions.
4. (a) Ballistreri, F. A. J. Org. Chem. 1996, 61, 6381; (b)
Defoin, A. Synthesis 2004, 706.
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Commun. 2006, 7, 236; (c) Khenkin, A. M.; Neumann, R.
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7. There are two reports on sulfur transfer, and sulfur–
nitrogen transfer from molybdenum xanthates, see (a)cis-
dithiooxo-bis((N,N-diethyl)hydroxylamido(1-)-O,N)moly-
bdenum(VI) reacts with benzyl isonitrile and cyclohexyl
isonitrile to produce the corresponding thioureas. (a)
´
Byrne, J. J.; Vallee, Y. Tetrahedron Lett. 1999, 40, 489;
Interestingly, when propargylamine 4 was reacted with
1b, the cyclic thiazolidine derivative, 5-methylene-
thiazolidine-2-thione 5 was obtained in 48% yield.18a
Similarly, the reaction of 2-aminobutanol 6 resulted in
the formation of the oxozolidine derivative, 4-ethyl-
oxazolidine-2-thione 7 in 52% yield18b (Scheme 2).
Adam and co-workers have demonstrated that
Mo(O)(S2CNEt2)2, a Mo(VI) complex, reacts with an
isonitrile in the presence of sulfur donors (elemental sulfur
or propene sulfide) to furnish the corresponding isothio-
cyanates. See (b) Adam, W.; Bargon, R. M.; Bosio, S. G.;
Schenk, W. A.; Stalke, D. J. Org. Chem. 2002, 67, 7037.
8. (a) Schroeder, D. C. Chem. Rev. 1955, 55, 181; (b) Sarkis,
G. Y.; Faisal, E. D. J. Heterocycl. Chem. 1985, 22, 137.
9. Walpole, C.; Ko, S. Y.; Brown, M.; Beattie, D.; Campbell,
E.; Dickenson, F.; Ewan, S.; Hughes, G. A.; Lemaira, M.;
Lerpiniere, J.; Patel, S.; Urban, L. J. Med. Chem. 1998, 41,
3159.
In conclusion, we have developed a mild method for the
synthesis of thiourea derivatives using molybdenum
xanthates 1a and 1b.15 The present method also allows
the synthesis of cyclic systems such as thiozolidine and
oxazolidine derivatives in moderate yields.18 Further
study to determine the scope and application of this
reaction with a variety of Mo–xanthates is underway
in our laboratories.
10. (a) Chalina, E. G.; Chakarova, L. Eur. J. Med. Chem.
1998, 33, 975; (b) Stark, H.; Purand, K.; Ligneau, X.;
Rouleau, A.; Arrang, J.-M.; Garbarg, M.; Schwartz, J.-C.;
Schunack, W. J. Med. Chem. 1996, 39, 1157.
11. (a) Wang, J.; Li, H.; Yu, X.; Zu, L.; Wang, W. Org. Lett.
2005, 7, 4293, and references cited therein; (b) Seayad, J.;
List, B. Org. Biomol. Chem. 2005, 3, 719; (c) Pihko, P. M.
Angew. Chem., Int. Ed. 2004, 43, 2062; (d) Yoon, T. P.;
Jacobsen, E. N. Angew. Chem., Int. Ed. 2005, 44, 466; (e)
Hoashi, Y.; Okino, T.; Takemoto, Y. Angew. Chem., Int.
Ed. 2005, 44, 4032; (f) Vakulya, B.; Varga, S.; Csampai,
A.; Soos, T. Org. Lett. 2005, 7, 1967.
Acknowledgments
We are grateful to IISc for the financial support for the
above work. Our thanks are due to Prof. S. Chandra-
sekaran for the facilities, useful discussions and
encouragement.
12. (a) Mohanta, P. K.; Dhar, S.; Samal, S. K.; Ila, H.;
Junjappa, H. Tetrahedron 2000, 56, 629; (b) Aoyama, T.;
Murata, S.; Nagata, Y.; Takido, T.; Kodamari, M.
Tetrahedron Lett. 2005, 46, 4875; (c) Kodomari, M.;
Suzuki, M.; Tanigawa, K.; Aoyama, T. Tetrahedron Lett.
2005, 46, 5841; (d) Bhandari, K.; Srivatsava, S.; Shankar,
G. Bioorg. Med. Chem. 2004, 12, 4289.
Supplementary data
Supplementary data (The spectral data, and 1H and 13
spectra of 3b, 3c, 3d, 3f, 3g, 3h, 3i, 3j, 5, and 7) associ-
ated with this article can be found, in the online version,
C
13. (a) Sharma, S. Synthesis 1978, 803; (b) Staab, H. A.
Angew. Chem., Int. Ed. Engl. 1962, 1, 351; (c) Staab, H. A.;