J . Org. Chem. 1999, 64, 4969-4971
4969
these reactions is the large amount of metal complex (ca.
30 mol %) required in order to complete the reaction. We
recently reported the preparation of copper(I) and iron-
(II) complexes that allow high reaction turnovers even
with a very low catalyst/substrate ratio (3 mol %).12
In this note, we describe the synthesis of two perfluo-
roalkylated polyamines as potential ligands for copper
or other transition metals. The copper complexes associ-
ated with a reducing agent (iron powder) allow the
radical cyclization of an unsaturated trichloro ester in
high yield using the FBS procedure with an efficient
recovery of the catalyst.
Cop p er (I) Com p lexes Med ia ted Cycliza tion
Rea ction of Un sa tu r a ted Ester u n d er
F lu or o Bip h a sic P r oced u r e
Floryan De Campo, Dominique Laste´coue`res,
J ean-Marc Vincent, and J ean-Baptiste Verlhac*
Laboratoire de Chimie Organique et Organome´tallique
(UMR 5802 CNRS), Universite´ Bordeaux I, 351 cours de la
Libe´ration, 33405 Talence Cedex, France
Received J anuary 26, 1999
The required perfluorinated ligands, the tri and tet-
radentate ligands 4 and 5 are prepared by standard
techniques for introduction of perfluoroalkyl chains.6,13
A three methylene carbon spacer is also introduced in
order to insulate the amine from the strong electron-
withdrawing effect of the perfluoroalkyl group. This
procedure has been already described and involves the
radical addition of perfluorooctyl iodide to allyl alcohol
to provide the iodo alcohol 1 (Scheme 1). Reduction of
compound 1 by tributyltin hydride afforded 2 in 88%
yield. Subsequent tosylation of compound 2 provided the
key material 3 for the peralkylation reaction of diethyl-
enetetramine and tris(aminoethyl)amine. The perfluori-
nated ligands 4 and 5 were obtained respectively in 65%
and 54% yields. These ligands are totally soluble in
perfluorohexane and could be purified by successive
washings with CH2Cl2.
We also used the permethylated ligand 6 as a reference
for reactions performed in nonperfluorinated medium.
The cyclization of pent-4-enyl trichloroacetate 7 was
realized in the presence of a 1:1 mixture of ligand and
copper(I) chloride. Under such catalysis, this substrate
has been reported to provide the endo lactone 8.11,12 We
reported that the use of ligand 6 (1 mol %) associated
with Cu(I)Cl resulted in a significantly enhanced yield
compared to CuCl/bipyridine (Scheme 2).12
Experiments with ligands 4 and 5 in the presence of
Cu(I)Cl were achieved in a fluorous biphasic procedure.
The use of a cosolvent (trifluorotoluene) allowed the
homogenization of the two phases at 80 °C although the
system remained biphasic at room temperature. The
results are collected in Table 1. Careful deoxygenation
of the reaction mixture was necessary as low traces of
dioxygen (even in the presence of a reducing agent)
considerably decrease the reaction yield, leading to
irreproducible results. When deoxygenation was per-
formed by the “freeze-pump-thaw” method (three cycles),
reproducible yields were obtained.
The concept of a “fluoro biphasic system” (FBS) has
been introduced recently by Horva´th and Raba´i.1 In this
approach, the catalyst is confined to the fluorocarbon
phase whereas the substrate and the reaction products
are dissolved in an organic solvent. The system is
biphasic at low temperature and becomes homogeneous
at a higher temperature. The major advantages of the
FBS is the very simple workup since the reaction
products remain in the organic phase, allowing easy
recovery of the catalyst for another reaction sequence.
Moreover, due to their chemical inertness, perfluorinated
compounds are environmentally friendly. This approach
has been applied for many organic reactions such as
organotin hydride reduction,2 Stille coupling reaction,3
or addition of allyl tin derivatives onto aldehydes.4
Oxidation reaction catalysts such as ruthenium or nickel
complexes,5 manganese,6 and cobalt or copper complexes7
as well as a hydroformylation catalyst8 or the fluorinated
analogue of Vaska’s complex9 have been prepared with
ligands bearing perfluoroalkyl side chains.
In this paper, we report an efficient FBS-based cataly-
sis for atom transfer radical additions (ATRA). This
technique uses a low valent metal to induce the radical
cleavage of a carbon-halogen bond. The metal-bonded
radical can react in a radical-like process. As the transi-
tion metal mediated cleavage of the carbon-halogen bond
is reversible, the reacted radical gives a new halogenated
product by reductive elimination and allows the recovery
of the catalyst at the end of the reaction.10 This concept
has been developed extensively by Speckamp and co-
workers to perform copper(I)-catalyzed radical cyclization
of unsaturated trichloro ester.11 The major drawback of
* Corresponding author. E-mail: j-b.verlhac@lcoo.u-bordeaux.fr.
(1) (a) Horva´th, I. T.; Raba´i, J . Science 1994, 266, 72. (b) Horva´th,
I. T.; Raba´i, J . U.S. Patent 5,463,082, 1995. (c) Cornils B. Angew.
Chem., Int. Ed. Engl. 1997, 36, 2057.
(2) Curran, D. P.; Hadida, S. J . Am. Chem. Soc. 1996, 118, 2531.
(3) Curran, D. P.; Hoshino, M. J . Org. Chem. 1996, 61, 6480.
(4) Curran, D. P.; Hadida, S.; He, M. J . Org. Chem. 1997, 62, 6714.
(5) Klement, I.; Lu¨tjens H.; Knochel, P. Angew. Chem., Int. Ed. Engl.
1997, 36, 1454.
Using the FBS procedure (entries 1 and 2 compared
to entry 3), the reaction proceeds slowly compared to the
(6) (a) Pozzi, G.; Banfi, S.; Manfredi, A.; Montanari, F.; Quici, S.
Tetrahedron 1996, 52, 11879. (b) Vincent, J .-M.; Rabion, A.; Yachandra,
V. K.; Fish, R. H.. Angew. Chem., Int. Ed. Engl. 1997, 36, 2346. (c)
Pozzi, G.; Cinato, F.; Montanari, F.; Quici, S. Chem. Commun. 1998,
877.
(7) (a) Pozzi, G.; Cavazzini, M.; Quici, S.; Fontana, S. Tetrahedron
Lett. 1997, 38, 7605. (b) Pozzi, G.; Montanari, F.; Quici, S. Chem.
Commun. 1997, 69. (c) Mandal, A. K.; Khanna, V.; Iqbal, J . Tetrahe-
dron Lett. 1996, 37, 3769.
(8) Horva´th, I. T.; Kiss, G.; Cook, R. A.; Bond, J . E.; Stevens, P. A.;
Raba´i, J .; Mozeleski, E. J . J . Am. Chem. Soc. 1998, 120, 3133.
(9) Guillevic, M.-A.; Arif, A. M.; Horva´th, I. T.; Gladysz, J . A. Angew.
Chem., Int. Ed. Engl. 1997, 36, 1612.
(10) (a) Pirrung, F. O. H.; Hiemstra, H.; Speckamp, W. N. Tetrahe-
dron 1994, 50, 12415. (b) Baldovini, N.; Bertrand, M.-P.; Carrie`re, A.;
Nougier, R.; Plancher, J .-M. J . Org. Chem. 1996, 61, 3205. (c) Lee, G.
M.; Parvez, M.; Weinreb, S. M. Tetrahedron 1988, 44, 4671. (d)
Branchaud, B. P.; Yu, G. X. Organometallics 1993, 12, 4262. (e) Forti,
L.; Ghelti, F.; Pagnoni, U. M. Tetrahedron Lett. 1996, 37, 2077.
(11) (a) Pirrung, F. O. H.; Hiemstra, H.; Speckamp, W. N.; Kaptein,
B.; Schoemaker, H. E. Synthesis 1995, 458. (b)Pirrung, F. O. H.;
Hiemstra, H.; Kaptein, B.; Martinez Sobrino, M. E.; Petra, D. G.;
Schoemaker, H. E.; Speckamp, W. N. Synlett 1993, 739.
(12) De Campo, F.; Laste´coue`res, D.; Verlhac, J .-B. Chem. Commun.
1998, 2117.
10.1021/jo990134z CCC: $18.00 © 1999 American Chemical Society
Published on Web 05/29/1999