Table 2 Substrate scope with 1 mol% BF3ꢁEt2O in benzene
Azide 10
Phosphite
P(OMe)3
Reaction conditionsa
Time/h
Temperature/1C
Yield (%)
85
Product 11
A
B
2
2
80
80
P(OMe)3
P(OMe)3
A
B
2
2
80
80
89
88
A
B
2
2
80
80
P(OMe)3
P(OMe)3
P(OMe)3
A
B
2
2
80
80
84
78
84
A
B
2
2
80
80
A
B
2
2
80
80
P(OMe)3
A
B
2
2
80
80
80
P(OEt)3
P(OEt)3
A
B
5
5.5
80
80
98b
63
A
B
12
5
25
80
a
Conditions: (A) 1 equiv. azide, 1 equiv. P(OMe)3 or P(OEt)3. (B) 1 mol% BF3ꢁEt2O, benzene. The catalyst was added directly to the
b
phosphorimidate without intermediate work-up. For more details see the ESI. TMSOTf as catalyst.
compounds in catalysis and in organic synthesis as precursors
to secondary amines, this transformation is of high utility and
complements the Staudinger reduction pathway, which di-
rectly converts azides into primary amines.
7. R. N. Salvatore, C. H. Yoon and K. w. Jung, Tetrahedron, 2001,
57, 7785.
8. A. Zwierzak and J. Brylikowska-Piotrowicz, Angew. Chem., Int.
Ed. Engl., 1977, 16, 107; H. Takemura, G. Wen and
T. Shinmyozu, Synthesis, 2005, 17, 2845; Y. F. Zhao, G. J. Ji,
S. K. Xi, G. Tang, A. T. Song and S. Z. Wei, Phosphorus Sulfur
Relat. Elem., 1983, 18, 155.
9. For other examples of secondary allylic amine synthesis see:
B. Ramanathan and A. L. Odom, J. Am. Chem. Soc., 2006, 128,
9344; E. E. Lee and R. A. Batey, Angew. Chem., Int. Ed., 2004, 43,
1865; H. M. Sampath Kumar, S. Anjaneyulu, B. V. Subba Reddy
and J. S. Yadav, Synlett, 1999, 551.
The authors acknowledge financial support from the Ger-
man Science Foundation (DFG) within the Emmy-Noether
program (HA 4468/2-1) and the SFB 765, as well as the Fonds
der Chemischen Industrie (FCI, Liebig Stipendium to
C. P. R. H.).
10. Y. G. Gololobov and L. F. Kasukhin, Tetrahedron, 1992, 48,
1353; Y. G. Gololobov, I. N. Zhmurova and L. F. Kasukhin,
Tetrahedron, 1981, 37, 437.
Notes and references
1. For
a
recent review of phosphoramidite ligands see:
11. M. Koehn and R. Breinbauer, Angew. Chem., Int. Ed., 2004, 43,
3106.
A. J. Minnaard, B. L. Feringa, L. Lefort and J. G. de Vries,
Acc. Chem. Res., 2007, 40, 1267.
2. S. E. Denmark and G. L. Beutner, Angew. Chem., Int. Ed., 2008,
47, 1560.
3. S. E. Denmark and W.-j. Chung, Angew. Chem., Int. Ed., 2008, 47,
1890; S. E. Denmark, S. B. D. Winter, X. Su and K.-T. Wong,
J. Am. Chem. Soc., 1996, 118, 7404; S. E. Denmark,
R. A. Stavenger, X. Su, K.-T. Wong and Y. Nishigaichi, Pure
Appl. Chem., 1998, 70, 1469.
12. S. Braese, C. Gil, K. Knepper and V. Zimmermann, Angew.
Chem., Int. Ed., 2005, 44, 5188. For a recent example of secondary
amine synthesis via the alkylation of iminophosphoranes see:
S. Ayesa, B. Samuelsson and B. Classon, Synlett, 2008, 97.
13. B. Chen and A. K. Mapp, J. Am. Chem. Soc., 2005, 127, 6712;
B. Chen and A. K. Mapp, J. Am. Chem. Soc., 2004, 126, 5364.
14. B. C. Challis, J. A. Challis and J. N. Iley, J. Chem. Soc., Perkin
Trans. 2, 1978, 8, 813.
4. S. E. Denmark, D. M. Coe, N. E. Pratt and B. D. Griedel, J. Org.
Chem., 1994, 59, 6161; S. E. Denmark and J. Fu, Chem. Rev., 2003,
103, 2763; S. E. Denmark and J. Fu, Chem. Commun., 2003, 167.
5. O. Molt and T. Schrader, Synthesis, 2002, 18, 2633.
6. S. E. Denmark, X. Su, Y. Nishigaichi, D. M. Coe, K.-T. Wong, S.
B. D. Winter and J. Y. Choi, J. Org. Chem., 1999, 64, 1958.
15. This observation is in accordance with the results published by
Chen and Mapp (ref. 13) who reported that polar solvents
facilitate the intermolecular rearrangement of allylic phosphori-
midates in moderate yields.
16. E. J. Cabrita, C. A. M. Afonso and A. G. De Oliveira Santos,
Chem.–Eur. J., 2001, 7, 1455.
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