M. Kawatsura et al. / Tetrahedron Letters 49 (2008) 4873–4875
4875
(>98%).13,14 This result is in good agreement with the catalytic
reactions, and also supports the fact that the Ru3(CO)12/2-DPPBA
catalyst selectively forms linear-type allylic amines.
3.3 mol% Ru3(CO)12
10 mol% 2-DPPBA
N
+
3a
Ph
N
DBU, THF, 60 ºC
Ph
In conclusion, we demonstrated the Ru3(CO)12/2-DPPBA-cata-
lyzed linear selective allylic amination of monosubstituted allylic
acetates with secondary amines. The regioselectivity was highly
controlled by the Ru3(CO)12/2-DPPBA catalyst, and a linear-type
aminated product was obtained.
4a
3a
Scheme 4.
Table 4
Acknowledgements
Ruthenium-catalyzed isomerization of 3a to 4aa
This work was partially supported by a Grant-in-Aid for Scien-
tific Research from the Ministry of Education, Culture, Sports, Sci-
ence and Technology, Japan.
Entry
Time (h)
3a:4ab
1
2
3
4
12
24
53
89
97:3
83:17
58:42
51:49
References and notes
a
Reaction conditions: 3a (1.0 mmol), DBU (2.0 mmol), THF (0.2 mL).
b
The ratio was determined by 400 MHz 1H NMR analysis of crude materials.
1. (a) Jørgensen, K. A. In Modern Amination Methods; Ricci, A., Ed.; Wiley-VCH:
Weinheim, 2000. Chapter 1, pp 1–35; (b) Johannsen, M.; Jørgensen, K. A. Chem.
Rev. 1998, 98, 1689–1708.
2. Selected examples of transition metal catalyzed allylic aminations of allylic
esters: for [Pd]: (a) Dubovyk, I.; Watson, I. D. G.; Yudin, A. K. J. Am. Chem. Soc
2007, 129, 14172–14173; (b) Johns, A. M.; Liu, Z.; Hartwig, J. F. Angew. Chem.,
Int. Ed 2007, 46, 7259–7261; (c) Faller, J. W.; Wilt, J. C. Org. Lett. 2005, 7, 633–
636 and references cited therein; For [Ir]: (d) Takeuchi, R.; Ue, Naoki; Tanabe,
K.; Yamashita, K.; Shiga, N. J. Am. Chem. Soc. 2001, 123, 9525–9534; (e) Ohmura,
T.; Hartwig, J. F. J. Am. Chem. Soc. 2002, 124, 15164–15165; (f) Leitner, A.;
Shekhar, S.; Pouy, M. J.; Hartwig, J. F. J. Am. Chem. Soc. 2005, 127, 15506–15514;
(g) Polet, D.; Alexakis, A.; Tissot-Croset, K.; Corminboeuf, C.; Ditrich, K. Chem.
Eur. J. 2006, 12, 3596–3609; (h) Weihofen, R.; Tverskoy, O.; Helmchen, G.
Angew. Chem., Int. Ed. 2006, 45, 5546–5549 and references cited therein; For
[Rh]: (i) Evans, P. A.; Robinson, J. E.; Nelson, J. D. J. Am. Chem. Soc. 1999, 121,
6761–6762; (j) Evans, P. A.; Robinson, J. E.; Nelson, J. D. J. Am. Chem. Soc. 1999,
121, 12214.
3. Examples of ruthenium-catalyzed allylic aminations of allylic esters: (a)
Morisaki, Y.; Kondo, T.; Mitsudo, T. Organometallics 1999, 18, 4742–4746; (b)
Matsushima, Y.; Onitsuka, K.; Kondo, T.; Mitsudo, T.; Takahashi, S. J. Am. Chem.
Soc. 2001, 123, 10405–10406; (c) Matsushima, Y.; Onitsuka, K.; Takahashi, S.
Organometallics 2004, 23, 3763–3765.
4. (a) Kondo, T.; Ono, H.; Satake, N.; Mitsudo, T.; Watanabe, Y. Organometallics
1995, 14, 1945–1953; (b) Kondo, T.; Mitsudo, T. Curr. Org. Chem. 2002, 6, 1163–
1179.
5. (a) Mbaye, M. D.; Demerseman, B.; Renaud, J.-L.; Toupet, L.; Bruneau, C. Angew.
Chem., Int. Ed. 2003, 42, 5066–5068; (b) Mbaye, M. D.; Demerseman, B.;
Renaud, J.-L.; Bruneau, C. J. Organomet. Chem 2005, 690, 2149–2158; (c) Renaud,
J.-L.; Demerseman, B.; Mbaye, M. D.; Bruneau, C. Curr. Org. Chem. 2006, 10,
115–133.
6. Fernández, I.; Hematschweiler, R.; Pregosin, P. S.; Albinati, A.; Rizzato, S.
Organometallics 2006, 25, 323–330.
7. Recently, regio- and enantio-selective allylic etherfication of mono-substituted
allyl compounds was reported, see: Onitsuka, K.; Okuda, H.; Sasai, H. Angew.
Chem., Int. Ed. 2008, 47, 1455–1457.
8. (a) Kawatsura, M.; Ata, F.; Wada, S.; Hayase, S.; Uno, H.; Itoh, T. Chem. Commun.
2007, 298–300; (b) Kawatsura, M.; Ata, F.; Hayase, S.; Itoh, T. Chem. Commun.
2007, 4283–4285.
9. For examples, see: (a) Felpin, F.-X.; Landais, Y. J. Org. Chem. 2005, 70, 6441–
6446; (b) Hierso, J.-C.; Fihri, A.; Amardeli, R.; Meunier, P.; Doucet, H.; Santelli,
M. Tetrahedron 2005, 61, 9759–9766; (c) Ooe, M.; Murata, M.; Takahama, A.;
Mizugaki, T.; Ebitani, K.; Kaneda, K. Chem. Lett. 2003, 32, 692–693; (d)
Feuerstein, M.; Laurenti, D.; Doucet, H.; Santelli, M. Tetrahedron Lett. 2001, 42,
2313–2315.
10. We confirmed that large amount of undesired 3-phenyl-1-propene (>50%) was
formed.
11. Zhang, S.-W.; Mitsudo, T.; Kondo, T.; Watanabe, Y. J. Organomet. Chem 1993,
450, 197–207.
Ph
+
Ph
N
+ 3a
60 ºC, THF
N
H
2a
Ru(II)(L)(CO)2
6 h
4a
5
100% conversion
90% isolated yield
(3a : 4a = 2 : >98)
(L = 2-DPPBA)
Scheme 5.
monosubstituted allyl acetates 1a and 1b proceeds through the
same
-allylruthenium intermediate.12
We next studied the reaction pathway of this linear selective
allylic amination by the Ru3(CO)12/2-DPPBA catalyst. As men-
tioned, the ruthenium-catalyzed isomerization of branched allylic
p
amines into their linear isomers is a known process in p-allylruthe-
nium chemistry.4–6 Based on this previous observation, we exam-
ined the isomerization of the branch-type allylic amine 3a into
the linear-type allylic amine 4a using the Ru3(CO)12/2-DPPBA cat-
alyst. Allylic amine 3a was treated with Ru3(CO)12 (3.3 mol %), 2-
DPPBA (10 mol %) and DBU (2.0 equiv) in THF at 60 °C. The ratio
of 3a and 4a was measured by the 1H NMR spectrum of the crude
materials. As shown in Scheme 4 and Table 4, a trace amount of the
linear-type allylic amine 4a was produced in 12 h (entry 1), and the
amount of 4a slowly increased (entries 2 and 3). However, the ratio
of 3a to 4a was 51:49 after 89 h, and the reaction had almost
stopped (entry 4). This result revealed that our ruthenium catalyst
systems also catalyze the isomerization reaction from 3a to 4a, but
it was slow.
We earlier reported the linear selective nucleophilic attack by
malonate anion on the
was generated from either the regioisomeric allyl acetates 1a or
1b using the Ru3(CO)12/2-DPPBA catalyst. Based on this previous
study, we anticipated that nitrogen nucleophiles also selectively
p
-allylruthenium intermediate 5,8a which
12. Phenyl group is necessary for this regioselectivity because the linear
selectivities in the reaction of methyl group substituted allyl acetate (3-
acetoxy-1-butene) with piperidine were 52% (60 °C, 12 h) and 51% (100 °C,
24 h).
attack the sterically less hindered
produce the linear-type aminated product. To prove this hypothe-
sis, we next examined the stoichiometric reaction of -allylruthe-
p-allyl terminus and directly
p
13. We also examined the same reaction for 1 h, then confirmed the 70%
conversion of the ruthenium complex 5 and the ratio of 3a/4a to be 2/>98 by
1H NMR analysis of crude materials.
14. The reaction of ruthenium complex 5 with primary amine 2m resulted in no
reaction, and recovered the complex 5.
nium complex 5 with 2a (Scheme 5). The complex 5 was treated
with 2a at 60 °C for 6 h, and we then confirmed by the 1H NMR
spectrum the 100% conversion (90% isolated yield after silica gel
column chromatography) and almost perfect linear selectivity