Fe-Catalyzed reactions of 2-chloro-1,7-dienes and allylmalonates

Article abstract of DOI:10.1016/j.tetlet.2007.04.143

Fe(III)(BIAP)Cl₃ complex catalyzes alkylative cyclization of 2-chloro-1,7-heptadiene in the presence of triethylaluminum. It also catalyzes deallylation of certain 2-allyl-2-substituted malonates under the same reaction conditions.

Full text of DOI:10.1016/j.tetlet.2007.04.143

Tetrahedron Letters 48 (2007) 4539–4541
Fe-Catalyzed reactions of 2-chloro-1,7-dienes and allylmalonates
a
b
b
a,c,
*
David Ne cˇ as, Pavel Drabina, Milo sˇ Sedl a´ k and Martin Kotora
a
Department of Organic and Nuclear Chemistry, and Center for Structural and Synthetic Application of Transition
Metal Complexes, Faculty of Science, Charles University, Hlavova 8, 128 43 Prague 2, Czech Republic
ˇ
b
Department of Organic Chemistry, Faculty of Chemical Technology, University of Pardubice, N a´ m. Ces. Legi ı´ 565,
5
32 10 Pardubice, Czech Republic
Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo n a´ m eˇ st ı´ 2,
66 10 Prague 6, Czech Republic
c
1
Received 23 February 2007; revised 19 April 2007; accepted 27 April 2007
Available online 3 May 2007
Abstract—Fe(III)(BIAP)Cl complex catalyzes alkylative cyclization of 2-chloro-1,7-heptadiene in the presence of triethylaluminum.
3
It also catalyzes deallylation of certain 2-allyl-2-substituted malonates under the same reaction conditions.
Ó 2007 Elsevier Ltd. All rights reserved.
Although iron is one of the most abundant metals found
in nature, the use of its compounds as catalysts for the
formation of C–C bonds in organic synthesis is rather
limited, especially in comparison with other transition
metals (Ni, Pd, Rh, etc.). Problems associated with the
use of the iron compounds as the catalysts often stem
from the fact that the catalytically active species are
sensitive to reaction conditions used and often lack gen-
erality with respect to the structure of reactants. On the
other hand, iron compounds are able to catalyze a
Because of our interest in the development of new Fe-
catalyzed reactions, we decided to search for a better
iron-based catalytic system, especially because Fe-phos-
phine complexes lack generality with respect to the
substrate. We envisioned that a change of the phospho-
rus-based ligand for a nitrogen-based one (BIAP = bis-
(imidazolonyl)pyridine) could result in the formation
of more powerful catalysts. This assumption was based
on the results obtained during Rh-catalyzed deallyl-
ations, in which it was clearly demonstrated that the
BIAP ligated complexes are more catalytically active
1
plethora of interesting transformations, and are thus
7
attractive targets for further research. In iron-catalyzed
cross-coupling reactions, for example, after pioneering
then those with phosphines.
2
work by Kochi in the early 1970s, iron catalyzed pro-
At the outset, the starting Fe(III)(BIAP)Cl3 1a–e
cesses made a comeback in the work of F u¨ rstner and
Knochel, who showed its generality.
complexes were prepared according to the previously
reported procedure (Fig. 1). As a test reaction we chose
3
,4
8
alkylative cyclization of 9-allyl-9-(2-choroallyl)-9H-fluo-
rene 2. The reaction was carried out under standard con-
ditions. The results obtained are presented in Table 1.
In all cases the reaction was almost complete within
1 h and prolonging the reaction time to 24 h did not
result in substantial improvement in the yield of the
cyclized product 3. This is in sharp contrast with
We have recently reported a new process: an alkylative
cyclization of 2-chloro-1,7-dienes in the presence of a
catalytic amount of a Fe-phosphine complex and tri-
alkylaluminums. The main feature of this reaction was
an unprecedented iron-catalyzed alkyl group (Et, Me)
transfer from the trialkylaluminum to the cyclized
9
5
products. In addition we observed that under the same
reaction conditions certain allylmalonate substrates
underwent deallylation. The latter process was later
shown to proceed also under Ni- and Rh- catalyses.
2
1
a, R1 = CH(CH ) , R = Me
Bn
N
Bn
N
3 2
1
2
6
7
1b, R = Ph, R = Me
1
1
N
c, R1 = CH CH(CH ) , R = Me
2
O
O
2
3 2
2
N
R2
Fe
Cl
N
1
d, R = C(CH ) , R = Me
3
3
R1
R1
Cl
Cl
1
2
R2
1e, R = R = Me
*
Corresponding author. Tel.: +420 221 951 334; fax: +420 221 951
26; e-mail: kotora@natur.cuni.cz
3
Figure 1. Fe(III)(BIAP)Cl
3
complexes 1a–e.
0040-4039/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2007.04.143

4540
D. Ne cˇ as et al. / Tetrahedron Letters 48 (2007) 4539–4541
a
a
Table 1. Alkylative cyclization catalyzed by 1a–e
Table 2. Deallylation catalyzed by Fe(III)(BIAP)Cl
Fe-cat. 1a
3
complex 1a
EtOOC
Et Al
EtOOC
H
3
Fe-cat. 1
Et
Cl
H+
EtOOC
R
EtOOC R
Et Al
3
4
5
b
Malonate 4
R
5, Yield (%)
2
3
4
a
5a, 13
b
Catalyst 1
t (h)
3, Yield (%)
c
Me
1a
1b
1c
1d
1e
1
35 (53)
4
b
5b, 26
c
2
2
2
2
2
4
48 (61)
1
4
11
27
Cl
c
4
c
5c, 83 (48)
1
4
26
38
c
4
d
5d, 59 (45)
1
4
30
38
4e
5e, 38
5f, 91
1
4
26
36
4
f
a
b
c
5
mol % of the catalyst.
GC yields.
5 mol % of the catalyst.
a
5
3
mol %; Et Al, 200 mol %, 20 °C, 24 h.
b 1
H NMR yields.
1
1
c
h.
Fe-phosphine catalysts, where the yield gradually
increased with the reaction time. As for the catalytic
activity, the best yield of 3 was obtained with catalyst
dent on the structure of substrates and is rather unpre-
dictable. The scope of the reaction with respect to
other substrates as well as further elaboration of the
ligand structure is under investigation. Spectral charac-
1
a. It was slightly higher when 15 mol % of 1a was used
(
see Table 2).
1
13
teristics ( H and C NMR) of all formed compounds
6
,7
were in agreement with the previously published data.
Next we turned our attention to the deallylation
reaction, because in our previous experiments the Fe-
phosphine complex catalyzed the reaction only with
Acknowledgements
5
allyl(chloroallyl)malonate 4c. Catalyst 1a was used be-
cause it had proved to be the most active catalyst in the
alkylative cyclization, and reactions were carried out
We gratefully acknowledge financial support by the
Ministry of Education of the Czech Republic to the
Center for Structural and Synthetic Application of
Transition Metal Complexes (Project No. LC06070),
the Project MSM 002 162 7501, and the Project MSM
1
0
under standard conditions. The deallylation of diallyl-
malonate 4a proceeded with low conversion giving only
a low yield (13%) of allylmalonate 5a together with
recovered starting material. Similarly allyl(methal-
lyl)malonate 4b was deallylated and also in low yield
giving only 26% of methallylmalonate 5b. On the other
hand, the deallylation of allyl(chloroallyl)malonate 4c
gave rise to the deallylated product, (chloroallyl)malo-
nate 5c, in high 83% yield (48% after 1 h). Also, the
deallylation of butyl(allyl)malonate 4d proceeded to a
reasonable extent: butylmalonate 5d was formed in
0
02 162 0857.
References and notes
. For reviews, see: (a) Bolm, C.; Legros, J.; Le Paih, J.; Zani,
1
L. Chem. Rev. 2004, 104, 6217–6254; (b) F u¨ rstner, A.;
Martin, R. Chem. Lett. 2004, 34, 624–629; (c) Ne cˇ as, D.;
Kotora, M. Chem. Listy 2006, 100, 967–973.
5
9% yield (45% in 1 h). The efficiency of deallylation fell
again in the case of allylbenzylmalonate 4e, which gave
only 38% of 5e. Surprisingly, almost quantative deallyl-
ation was observed for allylphenylmalonate 4f: 91% of
2
3
4
. (a) Tamura, M.; Kochi, J. K. J. Am. Chem. Soc. 1971, 93,
1487–1489; (b) Tamura, M.; Kochi, J. K. Bull. Chem. Soc.
Jpn. 1971, 44, 3063–3073; (c) Tamura, M.; Kochi, J. K.
Synthesis 1971, 303–305; (d) Kochi, J. K. Acc. Chem. Res.
5
f. Attempts to deallylate diallylcoumaranone failed
1
974, 7, 351–360.
. (a) F u¨ rstner, A.; Leitner, A. Angew. Chem., Int. Ed. 2002,
1, 609–612; (b) F u¨ rstner, A.; Leitner, A.; M e´ ndez, M.;
completely, the starting material remaining intact.
4
In summary, we have shown that Fe(III)-BIAP com-
plexes 1 can catalyzed alkylative cyclization, the cata-
lytic activity of 1a being close to that of Fe-phosphine
Krause, H. J. Am. Chem. Soc. 2002, 124, 13856–13863; (c)
Scheiper, B.; Bonnenkessel, M.; Krause, H.; F u¨ rstner, A.
J. Org. Chem. 2004, 69, 3943–3949.
5
complexes. As for the deallylation, the reactions carried
. (a) Dohle, W.; Kopp, F.; Cahiez, G.; Knochel, P. Synlett
out in the presence of 1a gave better results than Fe-
phosphine complexes. Nonetheless, the results again
showed that the course of the reaction is highly depen-
2
001, 1901–1904; (b) Duplais, C.; Bures, F.; Sapountzis, I.;
Korn, T. J.; Cahiez, G.; Knochel, P. Angew. Chem., Int.
Ed. 2004, 43, 2968–2970; (c) Sapountzis, I.; Lin, W. W.;

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4541
Kofink, C. C.; Despotopoulou, C.; Knochel, P. Angew.
Chem., Int. Ed. 2005, 44, 1654–1658; (d) Dunet, G.;
Knochel, P. Synlett 2006, 407–410; (e) Lyle, F. R. U.S.
Patent 5 973 257, 1985; Chem. Abstr., 1985, 65, 2870.
. Ne cˇ as, D.; Kotora, M.; C ´ı sa rˇ ov a´ , I. Eur. J. Org. Chem.
complex 1a (0.025 mmol, 18 mg) in dry toluene (3 ml)
under argon was added Et Al solution in toluene (2 M,
1 mmol, 0.5 ml). The reaction mixture was stirred under
argon for 24 h at 20 °C. After that it was quenched with
water (1 ml) followed by 3 M solution of HCl (3 ml). The
3
5
6
2
004, 1280–1285.
. (a) Ne cˇ as, D.; Tursk y´ , M.; Kotora, M. J. Am. Chem. Soc.
004, 126, 10222–10223; (b) Ne cˇ as, D.; Tursk y´ , M.;
organic layer was separated and dried (MgSO
reaction mixture was analyzed by H NMR.
4
). Then the
1
2
10. A typical experimental procedure for deallylation reac-
tion. To a solution of 4 (0.5 mmol, 140 mg) and Fe-BIAP
complex 1a (0.025 mmol, 18 mg) in dry toluene (3 ml)
Ti sˇ lerov a´ , I.; Kotora, M. New J. Chem. 2006, 30, 671–674.
. Tursk y´ , M.; Ne cˇ as, D.; Drabina, P.; Sedl a´ k, M.; Kotora,
M. Organometallics 2006, 25, 901–907.
. Sedl a´ k, M.; Drabina, P.; C ´ı sa rˇ ov a´ , I.; R u˚ zˇ i cˇ ka, A.;
Hanusek, J.; Mach a´ cˇ ek, V. Tetrahedron Lett. 2004, 45,
7
8
3
under argon was added Et Al solution in toluene (2 M,
1 mmol, 0.5 ml). The reaction mixture was stirred under
argon for 24 h at 20 °C. After that it was quenched with
water (1 ml) followed by 3 M solution of HCl (3 ml). The
7
723–7726.
9
. A typical experimental procedure for alkylative cycliza-
tion. To a solution of 2 (0.5 mmol, 140 mg) and Fe-BIAP
organic layer was separated and dried (MgSO
reaction mixture was analyzed by H NMR.
4
). Then the
1