Copper-catalyzed synthesis of 1,2-disubstituted cyclopentanes from 1,6-dienes by ring-closing kharasch addition of carbon tetrachloride

Article abstract of DOI:10.1002/adsc.200800364

The reaction of carbon tetrachloride (CCl₄) with various 1,6-heptadienes catalyzed by copper homoscorpionate complexes affords cyclization products in moderate to high yields. The process involves the addition of the trichloromethyl radical to the diene followed by a 5-exo-trig cyclization reaction, resultingin the formation of the cis-3-chloromethyl-4-(2, 2,2-trichloroethyl)cyclopentane isomers in a highly regiospecific and stereospecific manner. We have studied the use of magnesium (Mg) as reducing agent for the regeneration of copper(I) catalysts. This method has afforded heterocycles in high yields even in the cases of diallyl ether (DAE) and tert-butyl N,N-diallylcarbamate (TBDAC).

Full text of DOI:10.1002/adsc.200800364

FULL PAPERS
DOI: 10.1002/adsc.200800364
Copper-Catalyzed Synthesis of1,2-Disubstituted Cyclopentanes
from 1,6-Dienes by Ring-Closing Kharasch Addition of Carbon
Tetrachloride
JosØ María MuÇoz-Molina,a Tomµs R. Belderraín,a,* and Pedro J. PØreza,*
a
Laboratorio de Catµlisis HomogØnea, Departamento de Química y Ciencia de los Materiales, Unidad Asociada al CSIC,
Campus de El Carmen s/n, Universidad de Huelva, 21007 Huelva, Spain
Fax : (+34)-959-219942; e-mail: perez@dqcm.uhu.es or trodri@dqcm.uhu.es
Received: June 11, 2008; Published online: September 26, 2008
Supportinginformation for this article is available on the WWW under
http://dx.doi.org/10.1002/adsc.200800364.
Abstract: The reaction of carbon tetrachloride We have studied the use of magnesium (Mg) as re-
(CCl4) with various 1,6-heptadienes catalyzed by ducing agent for the regeneration of copper(I) cata-
copper homoscorpionate complexes affords cycliza- lysts. This method has afforded heterocycles in high
tion products in moderate to high yields. The process yields even in the cases of diallyl ether (DAE) and
involves the addition of the trichloromethyl radical tert-butyl N,N-diallylcarbamate (TBDAC).
to the diene followed by a 5-exo-trig cyclization reac-
tion, resultingin the formation of the cis-3-chloro- Keywords: atom transfer radical addiiton (ATRA);
methyl-4-(2,2,2-trichloroethyl)cyclopentane isomers copper; Kharasch reaction; radical reactions; trispyr-
in a highly regiospecific and stereospecific manner. azolylborate ligands
Introduction
radical generation, i.e., the use of tris(trimethylsilyl)-
silane,[10] manganese(III) acetate,[11] dimanganese
AHCTREUNG
Ring-forming reactions, namely cyclization reactions, decacarbonyl,[12] samarium(II) iodide,[13] copper[5,14]
play a very important role in organic synthesis be- and ruthenium(II)[15] complexes, etc. Since the early
cause many natural organic molecules possess carbo- reports by Matyjazewski[16] concerningthe use of
and heterocyclic rings.[1] Over the past twenty years copper complexes as catalyst in atom transfer radical
there has been high demand by the pharmaceutical polymerization (ATRP), this catalytic system has
and fine chemical industries for the development of emerged as one of the most important in radical-con-
different synthetic methods to cyclic compounds, par- trolled transformations. ATRP processes involve a
ticularly for five-membered rings (i.e., cyclopentanes, first step that consists on a metal-catalyzed Kharasch
tetrahydrofurans, tetrahydropyrroles, etc).[2] Among reaction,[17] also designated as atom transfer radical
them, the transition metal-catalyzed cyclization reac- addition (ATRA, Scheme 1). The intramolecular ver-
tions of unsaturated substrates are undoubtedly one sion of the latter reaction, the so-called atom transfer
of the most useful synthetic procedures for the con- radical cyclization (ATRC, Scheme 1), has been ex-
[3]
struction of five-membered ringsystems.
Some of tensively studied over the last decade.[5]
the more commonly encountered methods are based
on oxidative addition,[4] radical cyclization,[5] cycloiso- the formation of five-membered rings via consecutive
merization,[6] and olefin metathesis processes.[7]
Kharasch addition of CCl4 to 1,6-heptadienes fol-
An interestingtransformation is the one leadingto
Free-radical reactions provide an effective tool for lowed by radical cyclization (Scheme 2). This reaction
the generation of carbon-carbon bonds, and, there- has been shown to be catalyzed by dimanganese deca-
fore, to obtain compounds by radical cyclization.[8] Or- carbonyl,[12] rhenium,[18] ruthenium,[18,19,20] rhodium[20]
ganotin hydrides dominate these kinds of processes, and iridium.[20] This reaction usually affords a mixture
in spite of the well-known drawback of the neurotox- of compounds from the cyclization (cis and trans iso-
icity of such reagents, that enforces the need for com- mers) or the simple ATRA reaction onto one or two
plex purification and separation steps.[9] This fact has double bonds. In spite of the well-known capabilities
led to the development of alternative methods for of several copper complexes to promote ATRP,
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tion of CCl4 with 1,w-dienes. Very high yields under
mild conditions have been obtained in the first exam-
ple of the use of copper in such transformations.
Results and Discussion
Addition ofCCl to 1,6-Hexadienes Catalyzed by
4
TpxCu Complexes
As a probe reaction, we chose three different diallyl-
malonates as the substrates to be reacted with CCl4 in
the presence of catalytic amounts of complexes 1–3
(Scheme 3). Such substrates are usually employed in
other metal-catalyzed cyclization processes, such as
ring-closing metathesis[19c,23] or cycloisomerization.[6]
A mixture of 100 equiv. of the correspondingdiallyl-
malonate and 400 equiv. of CCl4 in the presence of
1 equiv. of TpxCu in C6D6 (see Table 2) was main-
tained at 308C for 24 h and was then monitored by
1H NMR. Table 2 displays the results of this series of
Scheme 1. ATRA and ATRC reactions.
nine experiments, from which it is clearly observable
t-Bu,Me
that complex 1, containingthe Tp
ligand induced
the highest conversions. Complex 2 induced a lower
activity whereas the TpMs-containingcatalyst was in-
active at 308C. However, yields improved up to 80–
90% when carryingout the reaction at 70 8C. In all
cases the cis-isomer was preferentially formed, with
nearly no effect of the catalyst employed in the dia-
stereoselectivity. It is also worth mentioningthat this
system provides exclusively products 7–9, those corre-
spondingto the simple ATRA addition to the double
Scheme 2.
ATRA or ATRC processes, to the best of our knowl- bonds or alternate cyclization to 6-membered ring
edge the use of this metal for this transformation re- products were not observed.
mains unknown. We have recently reported that tris-
With the above results in hand, we decided to
pyrazolylborate copper complexes TpxCu(I) (Table 1) extend these studies to another three dienes: 1,6-hep-
display a remarkable activity in ATRA reactions,[21] tadiene, 10, diallyl ether (DAE), 11, and tert-butyl
that surpassed those of other previous Cu-based cata- N,N-diallylcarbamate (TBDAC), 12 (Table 2). For
lysts.[22] In this contribution we present the results ob- DAE and TBDAC, as for the diallylmalonate esters,
tained with these compounds as catalysts in the reac- only cyclization products are observed, but in the case
of heptadiene, the linear addition products are ob-
tained in 39, 16 and 12% yields for 1, 2 and 3 as cata-
lyst, respectively (Scheme 4).
Table 1. Homoscorpionate ligands employed in this work.
The results shown in Table 2 are, to the best of our
knowledge, the first example of copper-catalyzed cy-
clization reactions by this methodology, and compare
well with other results reported in the literature, using
other metal-based (Mn, Ru, Ir, Rh, Ru) cata-
lysts.[12,18,19,20] Mild conditions (308C) without the need
of irradiation[24] or heat for the generation of the radi-
cal species and relatively low charge of catalyst (1%)
are employed in our system. After these findings, we
focussed our attention in the understandingof this
transformation in order to improve the catalytic con-
versions.
Tpx
R1
R2
R3
1
2
3
Tpt-Bu,Me
TpCy,4Br
TpMs
Me
H
H
H
Br
H
t-Bu
C6H11
C6H2Me3
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Copper-Catalyzed Synthesis of 1,2-Disubstituted Cyclopentanes from 1,6-Dienes
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Scheme 3.
Table 2. Ring-closing Kharasch addition of CCl4 to 1,w-dienes catalyzed by TpxCu(I) complexes.[a]
Entry
1,6-Diene
TpxCu
Conversion [%][b]
Yield [%][b]
cis:trans[b]
kobs ”105 [sÀ1]
1
2
3
90
58
87 (<1)
90
58
87
93:7
90:10
91:9
12.8
6.7
9.9
1
4
1
2
3
83
48
90 (<1)
83
48
90
88:12
86:14
84:16
17.0
5.5
26.7
2
3
5
6
1
2
3
74
45
84 (<1)
74
45
84
86:14
84:16
84:16
16.3
7.9
39.2
1
2
3
98
77
93 (<1)
59
62
81
87:13
84:16
81:19
n.d.[c]
n.d.[c]
n.d.[c]
4
5
10
11
1
2
3
33
23
62 (<1)
33
23
62
77:23
70:30
71:29
6.5
1.0
2.6
1
2
3
41
25
88 (<1)
41
25
88
68:32
69:31
65:35
3.9
1.5
3.0
6
12
[a]
[catalyst]:
N
G
[b]
Conversions, yields and cis:trans ratios were determined by H NMR spectroscopy after 24 h. Reactions were carried out
at 308C with complexes 1 and 2, and 708C for 3 (parenthesis contain conversions at 308C).
n.d.: not determined.
[c]
Mechanistic Insights
the cyclization reaction, data in Table 1 show very
similar diastereoselectivities independently of the cat-
In our previous report about the use of copper-based alyst employed. Additional evidence was gained upon
catalysts for ATRA reactions,[21] we proposed the cat- carryingout the reaction of ethyl diallylmalonate and
alytic cycle shown in Scheme 5. The copper complex CCl4 in the presence of Tp*Cu [Tp*=tris(3,5-dime-
is responsible of the generation of the radical species thylpyrazolyl)borate], with the low sterically demand-
that further interacts with the olefin with no participa- ingTp*. As previously described for the Kharasch ad-
tion, at this stage, of the metal center. In the case of dition reaction of CCl4 to other olefins,[21] Tp*Cu only
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JosØ María MuÇoz-Molina et al.
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Scheme 4. Ring-closing Kharasch addition of CCl4 to 1,w-dienes catalyzed by TpxCu(I) complexes.
H 1,3-pseudodiaxial interactions would lead to the cis
isomer, whilst other possible transition states B and C
with more severe interactions CO2R/CHCCl3 (B) or
CO2R/CH=CH2, would afford the trans stereoisomer
(Scheme 6).
As detailed above (Scheme 2), these reactions pro-
vide not only cyclopentane derivatives but, in some
cases, products derived from the simple ATRA reac-
tion into one or two double bonds, the latter being
observed only in the case of 1,6-heptadiene with these
copper-based catalysts. Once the radical (Scheme 7, I)
is formed, two competitive reactions could occur: the
cyclization reaction or the linear addition, the latter
beinginduced by the reaction of the radical with
TpxCuCl. The respective reaction rates for these pro-
cesses are kC and kl, respectively. It has been already
proposed for the organostannane-mediated[29] cycliza-
tion of 6-hepten-2-radicals that an oxygen-containing
radical affords a higher kC/kl than the methylene one,
and the former cyclizes much more rapidly than the
later. This process seemed to be independent of the
concentration of the species I but dependent of the
Scheme 5. Mechanistic proposal for ATRA reactions cata-
lyzed by TpxCu complexes.
afforded low yields of the cyclization products (15%) nature of the radical. As shown in Table 2, the addi-
and with the same diastereoselectivity as previously tion of CCl4 to DAE or TBDAC, after 24 h, using 1
observed with complexes 1–3 (cis:trans ratio: 95:5). or 2 as catalyst provided moderate to low conversions
These results can be interpreted as a consequence of and lower rates, possibly due to the coordination of
a similar pathway in which the copper complex is not the substrate to the metal center which then forbids
involved in the cyclization steps, and only in the radi- the interaction with the CCl4 to generate the CCCl3
cal formation.
and to catalyst decomposition.
Various explanations have been developed to ac-
count for the regioselectivity of these radical cycliza-
tions, i.e., the selective formation of 5-membered
rings (5-exo-trig pathway), such as entropic,[25] steric[26]
and stereoelectronic factors.[27] It is known that 1-sub-
stituted hex-5-enyl radicals give predominantly cis-
1,2-disubstituted cyclopentene on cyclization.[28]
Moreover, it has been also proposed that in substrates
such as diallylmalonates the stereoselectivity could be
due to steric effects in the transition states.[18] Thus,
once the organic radical is formed, the less sterically
demandingtransition state A (Scheme 6) with CO2R/ Scheme 6. Transition states for the cyclization reaction.
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Copper-Catalyzed Synthesis of 1,2-Disubstituted Cyclopentanes from 1,6-Dienes
FULL PAPERS
Scheme 7. Kharasch addition of CCl4 to 1,w-dienes catalyzed by TpxCu(I) complexes.
The results found for the addition of CCl4 to 1,6- alyzed ATRP systems, for which Matyjaszewski et al.
heptadiene with our Cu-based catalyts seem to indi- have recently introduced the concept of initiators for
cate that there is a relationship between the ratio of continuous activator regeneration (ICAR).[30,31] This
cyclization to linear addition products and the activity strategy is based in the use of a constant source of or-
of the catalyst. Therefore, for the most active catalyst, ganic free radicals to regenerate the Cu(I) activator,
Tpt-Bu,MeCu (1), such a ratio was ca. 1.5, whereas for which is otherwise consumed in termination reactions.
TpCy,4BrCu (2) and TpMsCu (3) respective values of ca. After this report, Severin[32] and Pintauer[33] have em-
3.9 and 6.7 were observed. We interpret these results ployed the same technique in ATRA reactions cata-
in the followingmanner. The more active catalyst
lyzed by ruthenium and copper complexes, respective-
would generate a high concentration of I and this ly. One of the possible reducingagents is AIBN, but
could favor the termination step by reaction with the use of this compound has some problems. For in-
TpxCuCl. On the other hand, a less active catalyst stance, the reactions have to be heated in order to
would induce lower concentrations of I, allowingthe
intramolecular cyclization.
make AIBN an efficient radical source, and at high
temperature, it can initiate polymerization of the ole-
fins. In case of TpxCu complexes, 1 and 2 catalyze the
reaction at 308C, so it was important to try a reducing
agent which works under mild conditions. A second
agent reported by Severin and co-worker was metallic
magnesium.[32] On the basis of these findings, we de-
Enhanced Catalytic Activity by the Presence of
Additives: the Magnesium Effect
The main problem found with these catalysts for the cided to try the use of Mgin the Kharasch addition of
ring-closing Kharasch addition of CCl4 to 1,w-dienes CCl4 to a series of dienes (4, 5, 11 and 12), using 1
is the deactivation of the catalyst involvingradical ter-
and 2 as catalyst (Scheme 8). Water was employed to
mination, disproportionation or oxidation reactions. activate the Mgsurface.
This usually occurs due to a side reaction in which
The results are shown in Table 3, from which it can
radicals collapse. In ATRA reactions, for instance be observed that very high to quantitative conversions
(Scheme 5), CCl3 radical undergoes homocoupling to were observed in all cases, even for the case of DAE,
give C2Cl6, that was detected in the absence of olefins. makingthis strategy an alternative to others such cy-
Such behavior leads to accumulation of the Cu(II) cloisomerization[6] or RCM.[23] The effect of Mgseems
species, and therefore the initiatingCu(I) species
cannot be regenerated, therefore diminishing the cat-
alytic activity. This same proposal was made by Sever-
in and co-worker[29] for a Ru(II)-based system for
À
ATRA reactions, in which accumulation of Ru
Cl complexes induced a decrease of the catalytic
A
rates. This problem is also of relevance in copper-cat- Scheme 8.
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JosØ María MuÇoz-Molina et al.
Table 3. Ring-closing Kharasch addition of CCl4 to 1,6-dienes catalyzed by TpxCu(I)[a] complexes in presence of Mg.[b]
FULL PAPERS
Entry
1,6-Diene
TpxCu
Conversion [%][c]
Yield [%][c]
cis:trans[d]
1
2
>99
>99
>99
>99
93:7
90:10
1
4
1
2
>99
96
>99
96
88:12
87:13
2
3
5
1
2
>99
>99
>99
>99
86:14
82:18
11
12
1
2
95
90
95
90
87:13
83:13
4
[a]
[catalyst]:[1,6-diene]:[CCl4]=1:100:400; [cat]=11.0 mM; solvent, benzene-d6; reactions were carried out at 308C.
A
[b]
[c]
[d]
The reactions were performed in the presence of activated Mgpowder in benzene- d6 saturated with D2O.
1
Conversions and yields were determined by H NMR spectroscopy after 24 h.
cis:trans ratio determined from the 1H and 13C NMR spectra.
to be the reduction of Cu(II) to the Cu(I) active spe- plays a very good activity/cost ratio. We are currently
cies for radical formation, avoidingthe deactivation extendingthese findinsg to other copper-catalyzed
of the catalytic system. The diastereoselectivities are radical reactions.
similar to those found in the absence of magnesium
(Table 2) for 4 and 5, but the cis diastereoselection in-
creases for 11 and 12. Once again there seems not to Experimental Section
be an influence of the copper center duringthe cycli-
zation process and the observed increase in the per- General Information
centage of cis isomer for the later maybe due to coor-
The homoscorpionate ligands were prepared according to
dination of the substrate to the magnesium during the
literature methods as well as the complexes TpXCu[35] and
diisopropyl and dibenzyl malonates, 5 and 6.[36] All other
startingmaterials and reaegnts were purchased from Al-
drich, and were purified as follows: carbon tetrachloride was
distilled and substrates were filtered on alumina columns
prior to use. NMR experiments were run in a Varian Mercu-
ry 400 MHz spectrometer. All preparations were carried out
in a glove box under nitrogen.
reaction.[34]
Conclusions
We have described the use of the TpxCu(I) complexes
as good catalysts in ring-closing Kharasch addition of
CCl4 to 1,w-dienes, affordingthe correspondingfive-
membered hetero- and carbocycles in yields which
vary from moderate to high. In the case of 1,6-hepta-
diene only are linear addition products formed, the
reaction beingreigoselective toward ringproducts
with the other substrates. The cis:trans ratio is inde-
pendent of the catalyst, but the regioselectivity be-
tween rings and linear products depends of the cata-
lyst activity. The use of magnesium as co-catalyst has
led to very high to quantitative conversions, under
General Procedure for the Ring-Closing Kharasch
Addition ofCCl to Diolefins
4
A solution of the diolefin (0.821 mmol), the corresponding
TpxCu complex (8.21”10À3 mmol from a stock solution) and
CCl4 (3.285 mmol) were dissolved in the required amount of
C6D6 to complete a total volume of 820 mL. The final con-
centrations were [catalyst]=10.0 mM, [olefin]=1.0M,
[CCl4]=4.0M. The solution was transferred into a pressure
NMR tube and sealed with a Teflon screw cap. The tube
mild conditions. This Mg-TpxCu catalytic system dis- was removed from the glove box and placed in an oil bath
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Copper-Catalyzed Synthesis of 1,2-Disubstituted Cyclopentanes from 1,6-Dienes
FULL PAPERS
1
at 308C. The conversions were analyzed by H NMR spec-
troscopy at the desired times.
Angew. Chem. Int. Ed. 2004, 43, 4063–4067; f) C.
Bçing, G. Franciò, W. Leitner, Chem. Commun. 2005,
1456; g) C. Bçing, J. Hahne, G. Franciò, W. Leitner,
Adv. Synth. Catal. 2008, 350, 1073–1080; h) S. Park, D.
Takeuchi, K. Osakada, J. Am. Chem. Soc. 2006, 128,
3510; i) Y. J. Song, I. G. Jung, H. Lee, Y. T. Lee, Y. K.
Chung, H. Y. Jang, Tetrahedron Lett. 2007, 48, 6142–
6146; j) C. J. Diez-Holz, C. Bçing, G. Franciò, M.
Holscher, W. Leitner, Eur. J. Org. Chem. 2007, 2995–
3002.
General Procedure for the Ring-Closing Kharasch
Addition ofCCl to Diolefins in the Presence of Mg
4
A solution of the diolefin (0.821 mmol), the corresponding
TpxCu complex (8.21·10À3 mmol from a stock solution) and
CCl4 (3.285 mmol) were disolved in the required amount of
C6D6 to complete a total volume of 820 mL. This solution
was added to a vial that contained Mgpowder (100 mg) and
D2O (20 mL). The mixture was stirred for 24 h (308C). After
addition of 50 mL of dioxane (in order to avoid the coordi-
nation of magenesium to the products), a sample was re-
moved from the final mixture, filtered on alumina column,
[7] See for example: a) S. BouzBouz, L. Boulard, J. Cossy,
Org. Lett. 2007, 9, 3765–3768; b) G. Y. Liu, J. Z.
Zhang, B. Wu, J. H. Wang, Org. Lett. 2007, 9, 4263–
4266; c) K. C. Majumdar, H. Rahaman, B. Roy, Curr.
Org. Chem. 2007, 11, 1339–1365; d) G. Occhipinti,
H. R. Bjorsvik, K. W. Tornroos, V. R. Jensen, Organo-
metallics 2007, 26, 5803–5814; e) D. Rix, F. Caijo, I.
Laurent, L. Gulajski, K. Grela, M. Mauduit, Chem.
Commun. 2007, 3771–3773; f) O. Trapp, S. K. Weber, S.
Bauch, W. Hofstadt, Angew. Chem. Int. Ed. 2007, 46,
7307–7310.
1
and analyzed by H NMR.
Kinetic Studies
The kinetic experiments were performed in a manner simi-
lar to that described for the standard catalytic system. The
total volume of the solution was maintained at 820 mL by
[8] a) C. D. Edlin, J. Faulkner, M. Helliwell, C. K. Knight,
J. Parker, P. Quayle, J. Raftery, Tetrahedron 2006, 62,
3004–3015; b) K. I. Kobrakov, A. V. Ivanov, Chem.
Heterocycl. Compd. 2001, 37, 529–539; c) K. C. Ma-
jumdar, P. P. Mukhopadhyay, P. K. Basu, Heterocycles
2004, 63, 1903–1958; d) K. C. Majumdar, P. K. Basu,
P. P. Mukhopadhyay, Tetrahedron 2004, 60, 6239–6278;
e) T. R. Rheault, M. P. Sibi, Synthesis 2003, 803–819.
[9] P. A. Baguley, J. C Walton, Angew. Chem. Int. Ed.
1998, 37, 3072.
addingsufficient C D6 (see SupportingInformation).
6
Supporting Information
NMR data for the products, reaction NMR spectra of reac-
tion mixtures and kinetic plots are available as Supporting
Information.
Acknowledgements
[10] C. Chatgilialoglu, Acc. Chem. Res. 1992, 25, 188–194.
[11] B. B. Zinder, Chem. Rev. 1996, 96, 339–363.
[12] a) B. C. Gilbert, W. Kalz, C. I. Lindsay, P. T. McGrail,
A. F. Parsons, D. T. E. Whittaker, J. Chem. Soc. Perkin
We thank the MEC (Proyecto CTQ2005–00324BQU) and
the Junta de Andalucía (Proyecto P07-FQM-02794) for fi-
nancial support. J. M. M.-M. thanks the Universidad de
Huelva for a research fellowship.
Trans.
1 2000, 8, 1187–1194; b) N. Huther, P. T.
McGrail, A. F. Parsons, Eur. J. Org. Chem. 2004, 1740–
1749.
[13] G. A. Molander, C. R. Harris, Chem. Rev. 1996, 96, 307.
[14] For recent reports see: a) A. J. Clark, J. V. Geden, S.
Thom, J. Org. Chem. 2006, 71, 1471–1479; b) A. J.
Clark, J. V. Geden, S. Thom, P. Wilson, J. Org. Chem.
2007, 72, 5923–5926.
[15] For recent reports see for example: a) V. Dragutan, I.
Dragutan, L. Delaude, A. Demonceau, Coord. Chem.
Rev. 2007, 251, 765–794; b) K. Thommes, B. Icli, R.
Scopelliti, K. Severin, Chem. Eur. J. 2007, 13, 6899–
6907.
[16] J. S. Wang, K. Matyjaszewski, J. Am. Chem. Soc. 1995,
117, 5614.
[17] a) M. S. Kharasch, H. Engelmann, F. R. Mayo, J. Org.
Chem. 1938, 2, 288; b) M. S. Kharasch, E. V. Jensen,
W. H. Urry, Science 1945, 102, 128.
[18] R. Grigg, J. Devlin, A. Ramasubbu, R. M. Scott, P. Ste-
venson, J. Chem. Soc. Perkin Trans. 1 1987, 1515–1520.
[19] a) B. De Clercq, F. Verpoort, Cat. Lett. 2002, 83, 9–13;
b) B. De Clercq, F. Verpoort, J. Organomet. Chem.
2003, 672, 11–16; c) B. Schmidt, M. Pohler, J. Organo-
met. Chem. 2005, 690, 5552–5555; d) D. Derouet, J. C.
Brosse, Eur. Polym. J. 1991, 27, 1125–1140.
References
[1] a) T. Hudlicky, J. D. Price, Chem. Rev. 1989, 89, 1467–
1486; b) B. M. Trost, Chem. Soc. Rev. 1982, 11, 141–
170.
[2] J. Apsimon, The Total Synthesis of Natural Products,
Vol. 4, Wiley-Interscience, New York, 1981.
[3] A. Kotschy, G. Timµri, Heterocycles from Transition
Metal Catalysis: Formation and Functionalization,
Springer, Netherlands, 2005.
[4] a) M. Lautens, W. Klute, W. Tam, Chem. Rev. 1996, 96,
49–92; b) N. E. Schore, Chem. Rev. 1988, 88, 1081–
1119.
[5] A. J. Clark, Chem. Soc. Rev. 2002, 31, 1–11.
[6] a) K. L. Bray, G. C. Lloyd-Jones, M. P. MuÇoz, P. A.
Slatford, E. H. P. Tan, A. R. Tyler-Mahon, P. A. Wor-
thington, Chem. Eur. J. 2006, 12, 8650–8663; b) L. A.
Goj, ; G. A. Cisneros, W. T. Yang, R. A. Widenhoefer, J
Organomet. Chem. 2004, 689, 2845–2845; c) L. A. Goj,
R. A. Widenhoefer, J. Am. Chem. Soc. 2001, 123,
11133–11147; d) Y. J. Song, I. G. Jung, H. Lee, Y. T.
Lee, Y. K. Chung, H. Y. Jang, Tetrahedron Lett. 2007,
48, 6142–6146; e) Y. Terada, M. Arisawa, A. Nishida,
Adv. Synth. Catal. 2008, 350, 2365 – 2372
ꢀ 2008 Wiley-VCH VerlagGmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
2371

JosØ María MuÇoz-Molina et al.
FULL PAPERS
[20] A. E. Diaz-Alvarez, P. Crochet, M. Zablocka, C. Du-
hayon, V. Cadierno, J. P. Majoral, Eur. J. Inorg. Chem.
2008, 786–794.
[25] M. Julia, C. Descoins, M. Baillarge, B. Jacquet, D.
Uguen, F. A. Groeger, Tetrahedron 1975, 31, 1737–
1744.
[21] J. M. MuÇoz-Molina, A. Caballero, M. M. Diaz-Reque-
jo, S. Trofimenko, T. R. Belderrain, P. J. Perez, Inorg.
Chem. 2007, 46, 7725–7730.
[26] A. L. J. Beckwith, Tetrahedron 1981, 37, 3073–3100.
[27] N. O. Brace, J. Org. Chem. 1967, 32, 2711–2718.
[28] A. L. Beckwith, I. Blair, G. Phillipo, J. Am. Chem. Soc.
1974, 96, 1613–1614.
[22] a) M. Hajek, M. Kotora, F. Adamek, R. Davis, C.
Fischer, W. A. C. Joshu, Coll. Czech. Chem. Commun.
1996, 61, 774; b) R. Davis, K. Stephens, M. Hajek, J.
Mol. Cat. A. 1994, 92, 269; c) D. Villemin, F. Sauvaget,
M. Hajek, Tetrahedron. Lett. 1994, 35, 3537; d) M.
Kotora, M. Hajek, J. Fluor. Chem. 1993, 64, 101; e) M.
Kotora, M. Hajek, C. Dobler, Coll. Czech. Chem.
Commun. 1992, 57, 2622; f) M. Kotora, M. Hajek, J.
Mol. Cat. A. 1992, 77, 51; g) M. Hajek, P. Silhavy, Coll.
Czech. Chem. Commun. 1983, 48, 1710; h) M. Hajek, P.
Silhavy, J. Malek, Coll. Czech. Chem. Commun. 1980,
45, 3502.
[29] L. Quebatte, K. Thommes, K. Severin, J. Am. Chem.
Soc. 2006, 128, 7440–7441.
[30] K. Matyjaszewski, W. Jakubowski, K. Min, W. Tang, J.
Huang, W. A. Braunecker, N. V. Tsarevsky, Proc. Natl.
Acad. Sci. U.S.A. 2006, 103, 15309–15314.
[31] a) L. Mueller, W. Jakubowski, W. Tang, K. Matyjaszew-
ski, Macromolecules 2007, 40, 6464–6472; b) W. A.
Braunecker, K. Matyjaszewski, Prog. Polym. Sci. 2007,
32, 93–146.
[32] K. Thommes, B. Icli, R. Scopelliti, K. Severin, Chem.
Eur. J. 2007, 13, 6899–6907.
[23] For recent examples, see: a) S. H. Hong, R. H. Grubbs,
Org. Lett. 2007; 9, 1955–1957; b) T. Ung, A. Hejl,
R. H. Grubbs, Y. Schrodi, Organometallics 2004, 23,
5399–5401; c) G. Occhipinti, H. R. Bjorsvik, K. W.
Tornroos, V. R. Jensen, Organometallics 2007, 26,
5803–5814; d) D. Rix, F. Caijo, I. Laurent, L. Gulajski,
K. Grela, M. Mauduit, Chem. Commun. 2007, 3771–
3773; e) N. Ledoux, B. Allaert, S. Pattyn, H. V. Mierde,
C. Vercaemst, F. Verpoort, Chem. Eur. J. 2006, 12,
4654–4661.
[33] a) W. T. Eckenhoff, T. Pintauer, Inorg. Chem. 2007, 46,
5844–5846; b) W. T. Eckenhoff, S. T. Garrity, T. Pinta-
uer, Eur. J. Inorg. Chem. 2008, 563–571.
[34] Coordination of magnesium to the oxygen donor atoms
of the substrates duringthe cyclization step has been
proposed in: D. Yang, S. Gu, Y. L. Yan, N. Y. Zhu,
K. K. Cheung, J. Am. Chem. Soc. 2001, 123, 8612–
8613.
[35] S. Trofimenko, Scorpionates: The Coordination Chemis-
try of Polypyrazolylborate Ligands, Imperial College
Press, River Edge, NJ, 1999.
[24] The radical cyclization reactions which uses dimanga-
nese decacarbonyl work at room temperature, but pho-
[12]
[36] S. C. Shim, K. T. Huh, W. H. Park, Synthesis 1987, 1, 59.
tolysis and 10% catalyst loadingare needed. See ref.
2372
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ꢀ 2008 Wiley-VCH VerlagGmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2008, 350, 2365 – 2372