8042
N. Suryakiran et al. / Tetrahedron Letters 47 (2006) 8039–8042
Table 1 (continued)
Entry
Substrate
Producta
Time (min)
Yieldb (%)
99
22
23
24
25
10
05
05
05
N
N
H
O
O
O
NH2
98
99
99
N
O
H
HO
HO
F
H
NH2
N
O
O
F
COOMe
COOMe
H
NH2
N
O
O
a All compounds were characterized by 1H NMR and EIMS spectral data.
b Isolated yields after column chromatography.
(b) Raghavendra, N. S.; Kumar, B. P.; Longquin, H.
Tetrahedron Lett. 2006, 47, 389.
diamines were subjected to N-tert-butoxycarbonylation,
a mono-N-tert-butylcarbamate was formed in a very
good yield (entries 10 and 14). The N-tert-butylcarb-
amate is stable under the reaction conditions for 3–6 h
at room temperature. From these results (Table 1) it is
evident that La(NO3)3Æ6H2O is an excellent catalyst for
N-tert-butoxycarbonylation of amines under solvent-
free conditions.
2. Ravinder, K.; Reddy, A. V.; Krishnaiah, P.; Ramesh, P.;
Ramakrishna, S.; Laatsch, H.; Venkateswarlu, Y. Tetra-
hedron Lett. 2005, 46, 5475.
3. (a) Grehn, L.; Ragnarsson, U. Angew Chem., Int. Ed.
Engl. 1984, 23, 296; (b) Grehn, L.; Ragnarsson, U. Angew
Chem., Int. Ed. Engl. 1985, 24, 510; (c) Burk, M. J.; Allen,
J. G. J. Org. Chem. 1997, 62, 705.
4. Einhorn, J.; Einhorn, C.; Luche, J.-L. Synlett 1991, 37.
5. Guibe-Janpel, E.; Wakselamann, M. J. Chem. Soc., Chem.
Commun. 1971, 267.
6. Guibe-Janpel, E.; Wakselamann, M. Synthesis 1977, 772.
7. Itoh, M.; Hagiwara, D.; Kamia, T. Tetrahedron Lett.
1975, 16, 4393.
8. Kim, S.; Lee, J. I. Chem. Lett. 1984, 237.
9. Barcelo, G.; Senet, J.-P.; Sennyey, G. Synthesis 1986, 627.
10. (a) Basel, Y.; Hassner, A. J. Org. Chem. 2000, 65, 6368; (b)
Darnbrough, S.; Mervic, M.; Condon, S. M.; Burns, C. J.
Synth. Commun. 2001, 31, 3273.
11. Pandey, R. K.; Dagade, S. P.; Upadhyaya, R. K.;
Dongare, M. K.; Pradeep, K. Arkivoc 2002, 2, 28.
12. Chakraborti, K. A.; Sunay, V. Org. Lett. 2006, 8, 3259.
13. (a) Sharma, G. V. M.; Reddy, J. J.; Lakshmi, P. S.;
Krishne, P. R. Tetrahedron Lett. 2004, 45, 6963; (b)
Chankeshwara, S. V.; Chakraborti, A. K. Tetrahedron
Lett. 2006, 47, 1987; (c) Chakraborti, K. A.; Sunay, V.
Synthesis 2006, 2784; (d) Chakraborti, K. A.; Sunay, V.
Org. Biomol. Chem. 2006, 4, 2769.
Typical experimental procedure: To a mixture of amine
(1 mmol) and di-tert-butyl dicarbonate (1.2 mmol) was
added finely powdered La(NO3)3Æ6H2O (5 mol %) and
the reaction mixture was stirred under solvent-free con-
ditions at room temperature for an appropriate time
(Table 1). After completion of the reaction as monitored
by TLC, water was added to the reaction mixture and
the product was extracted into ethyl acetate
(3 · 20 mL). The combined organic layer was washed
with brine, dried over anhydrous sodium sulfate and
concentrated under reduced pressure to give a crude
product, which was purified by silica gel column chro-
matography to afford the corresponding N-tert-
butylcarbamate.
Acknowledgements
14. Reddy, T. S.; Ravinder, K.; Suryakiran, N.; Narasimhulu,
M.; Chinni Mahesh, K.; Venkateswarlu, Y. Tetrahedron
Lett. 2006, 47, 2341.
15. Reddy, S. M.; Reddy, Y. V.; Venkateswarlu, Y. Tetra-
hedron Lett. 2005, 46, 7439.
The authors are thankful to the CSIR, DOD and DBT,
New Delhi, India, respectively, for the financial support
and to the Director of Indian Institute of Chemical
Technology, for his encouragement.
16. Narasimhulu, M.; Chinni Mahesh, K.; Reddy, T. S.;
Rajesh, K.; Venkateswarlu, Y. Tetrahedron Lett. 2006, 47,
4381.
References and notes
17. Reddy, T. S.; Narasimhulu, M.; Suryakiran, N.; Chinni
Mahesh, K.; Venkateswarlu, Y. Tetrahedron Lett. 2006,
47, 6825.
1. (a) Green, T. W.; Wuts, P. G. M. Protecting Groups in
Organic Synthesis; John Wiley & Sons: New York, 1999;