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Novel Trimerization of Cyclopentadiene with a Homogeneous Bifunctional Palladium-Acid Catalyst System.

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Table 2. Proportions (“A)of the four possible couplings to Diels-Alder products for the 1,3-dienes 1 and 2 and for ?-methylbutadiene [8].
R = CMe,
phenylphosphane (Ig[L],/[Ni], > 0); comparison of the
thermal with the catalytic dimerization shows that, catalytically, three isomers are formed: 4a and 4b in appreciably
larger proportion than in the thermal dimerization, and 4c
in only slightly increased proportion. The isomer 4d, on
the other hand, is only formed thermally.
Received: September I , 1984:
revised: November 2, 1984 [Z 988 IE]
Publication delayed at authors’ request
German version: Angew. Chem. 97 (1985) 345
’TT &
[I] H. W. 6. Reed, J . Clrem. Soc. 1954. 1931.
[2] a) H. Breil, P. Heimbach, M . Kroner, H. Muller, G. Wilke, Makromol.
Cbenr. 69 (1963) 18; b) G. Wilke, J. Organornet. Chem. 200 (1980) 349.
[3] W. Brenner, P. Heimbach, H. Hey, E. W. Miiller, G. Wilke, Jusfur Liebigs Ann. Chenr. 727(1969) 161.
.Turn\ (41 rhe proportions of the diferent coupling partners
h e part [a]
Diene p a n [b]
H T + T H [dl
[a] Proportion of the dimers in which the ene was incorporated as head or
tail. [b] Proportion of the dimers in which the head or tail of the diene was
coupled with the terminal C atom of the ene components. [c] Sum of the HHand TT-coupled dimers. [d] Sum of the HT- and TH-coupled dimers.
reaction (yield < 15% for Ig[L],/[Ni],> +0.5). Nevertheless, this very retarded reaction is also clearly catalytic,
since the diene 1 thermally dimerizes to only 0.2% under
these reaction conditions in the absence of catalyst. For
diene 2, the slower uncatalyzed Diels-Alder reaction (yield
ca. 20%), in which the isomers 4a-4d are formed, is observed after “turning o f f ’ the catalysis by addition of tri-
[4] T. Bartik, R. Boese, P. Heimbach, H:G. Preis: 7’he concept of molecular
order effecrorr in orgunrc sjwhesis. Springer, Berlin, in press.
[ 5 ] P. W. Jolly in G. Wilkinson, F. G. A. Stone, E. W. Abel: Comprebensioe
Organomerallic Chembtry. Yo/. 8. Pergamon, Oxford 1982, p. 673.
[6] The series of experiments was carried out with a parent solution of
bis(cyclooctadiene)nickel(o) in diene/tolueoe; n-heaane served in the
GC analysis as internal standard for diene and catalyst. Triphenylphosphane was added in a benzene solution. After 6 h at 60‘C in sealed glass
ampules, the reaction mixtures were directly analyzed by gas chromatography (Perkin Elmer F20, 45m OVlOl glass capillary column). The concentration of catalyst was 16 mmol/L, the ratio nickel :diene 1 : 160. All
operations were carried out under argon. 1 was synthesized according to
[lo]; 2 by adaption of the procedure for 2-triethylsilyl-I,3-butadiene
[ I 11.
[7] A. Bax, R. Freeman, T. A. Frenkiel, M. H. Levitt, J . M a g n . Recon. 43
(1981) 478: review: R. Benn, H. Giinther, Angew. Chem. 95 (1983) 381;
Angew. Chem. Inr. Ed. Engl. 22 (1983) 390.
[8] H. Krische, Dissertation, Universitat Essen 1980.
191 a) F. Brille, P. Heimbach, J. Kluth, H. Schenkluhn, Angew. Chem. 91
(1979) 428; Angew. Chem. Int. Ed. Engl. 1X (1979) 400: b) C. A. Tolman.
J. W. Faller in L. H. Pignolet: Homugeneuus Catalwiisis with Metal Ph0.sphine Conrplere.s. Plenum, New York 1983, p. 69ff.
[lo] A. A. Korotkov, L. F. Roguleva. Zh. Org. Khim. I (1965) 1180.
[ I I ] M. Petrzilka. J. I. Grayson, S.vnthesic 1981. 753.
112) Since the differences between the ”C chemical shifts of 3a and 3b are
unexpectedly small, we recorded the ?D-INADEQUATE spectrum of
3b as a control. Especially noticeable are the similarities of the shifts of
C-3 and C-6, respectively, in 3a and 3b. The signals of 4b and 4d were
assigned by comparison with the other compounds.
Novel Trimerization of Cyctopentadiene with
a Homogeneous, Bifunctional
Palladium-Acid Catalyst System**
By Arno Behr and Wilhelm Keirn”
Dedicated to Professor Giinther Wilke on the occasion
of his 60th birthdaj>
Although bifunctional catalysts have found wide application in heterogeneous catalysis,[’] there are still only very
few corresponding examples of their use in homogeneous
catalysis.”’ Herein, we describe the synthesis of two hitherto unknown cyclopentadiene trimers using a novel, bifunctional, mixed catalyst comprising a palladium complex and a carboxylic acid (“Pd/H@”).
This preparative result indicates that bifunctional G%lytic systems can also play an important part in homogeneous catalysis with transition-metals.
In the trimerization of cyclopentadiene two isomers are
formed that can be preparatively separatedl3I and fully
Fig. I.Opposite effect 01 the dddilioii ol~tiiphenylphosphaneo n the reaction
rate (yield curves) in the Ni-catalyzed oligomerization of butadiene (activation) and 2-[err-butyl- 1.3-butadiene 1 (inhibition); L : Ni = 10: 1 .
3 14
0 I‘CH Verlag~gesellsrliafrmbH. 0.6940 Wernheim. 1985
[*] Prof. Dr. W. Keim, Dr. A. Behr
lnstitut fur Technische Chernie und Petrolchemie
der Technischen Hochschule
Worringer Weg I, D-5100 Aachen (FRG)
[**I We thank F. Nii/ and R . Decorzant. Firmenich SA (Geneva). for their
help with the analytical-spectroscopic work.
0570-0833/85/0404-0314 $ 02.50/0
Angeu,. Clrem. I n t . Ed. Engl. 24 11985) No. 4
characterized spectroscopically. On the basis of the 360MHz H-NMR and 90-MHz "C-NMR spectral4] and the
result of decoupling experiments the trimers were assigned
to the structures la and l b . In both isomers the cyclopentene ring bound to the norbornane system is oriented in
the endo position.
Ill a) J . Falbe, U. Hasserodt: Katalvsaforen. Tenside und Mineralolodditiue.
Thierne, Stuttgart 1978; b) J. R. Anderson, M. Boudart: C o r d p Science and Technology, Vol. I - V l , Springer, Berlin 198 I - 1984.
[21 G. C. A. Schuit. B. C. Gates, CHEMTECH 1983. 556, 693.
[31 Column with AgN03-impregnated SiOz. hexane/ether 99 : 1 (cf. Woelm
Information No. 49).
[4] 'H-NMR, la:fi=1.45(1), l.70(1), 1.95(1),2.02 (l),2.l1 (3),2.20(3), 2.58
(2), 2.65 (l), 2.97 ( I ) , 5.43 [I), 5.53 ( I ) , 5.68 (l), 5.72 (I); l b : 6=1.46 (I),
(1),5.55(1),5.67(1),5.72(1); "C-NMR, la:6=133.4(d), 131.4(d), 130.7
(d), 130.6 (d), 52.0 (d), 48.7 (d), 45.6 (d), 44.4 (d), 43.1 (d), 42.0 (d), 41.7
(d), 40.9 (t). 37.7 (d), 36.4 (t), 31.8 (t); I b : 6 = 133.5 (d), 131.4 (d), 130.7 (d).
130.5(d),52.3(d),48.5(d),47.3(d),44.1 (d),42.7(d),41.2(d),41.0(t+d),
38.0 (d), 36.5 (t), 31.7 (t).
(51 IR, l a , b [crn-'1: v=3040 5, 2930 s, 2840 m, 1640 sh, 1608 rn, 1470 m,
1438 m, 712 s, 725 sh. 698 sh.
[61 MS, l a , b ( m h ,rel. int. [Ole]): 198 (lo), 183 (I), 169 ( I ) , 157 ( I ) , 132 (20).
131 (8), 117 (6). 91 (lo), 66 (100).
The 1 : 1 mixture of the pentacyclo['0~14]pentadeca-4,12- l a and -4,ll-diene l b forms white fibrous
crystals (m.p. 4 9 T , b.p. 75 "C/O.Ol torr). No absorption
A New Method for Determining Enantiomeric
maxima are observed in the UV spectrum above 200 n m ;
Excess, where the Sample Serves as its Own
the IR spectrumi5' shows the typical C=C stretching band
at 1608 cm-' for the cyclopentene ring, while the stretchBy Maurice L. Pasquier and Werner Marty*
ing band of the norbornene ring at ca. 1570 cm-' characThe determination of the enantiomeric excess (ee) of a
teristic for Diels-Alder trimers is missing. The mass specnew,
chiral substance is usually based on diastereomeric
trum['' is also consistent with the proposed structures.
interactions between molecules of this substance and moIn the catalytic hydrogenation of l a and l b , 2 moles of
lecules of a different substance of known ee.L',zlHowever,
hydrogen are taken u p per mole, in each case with formameasurable
diastereomeric interactions between enantintion of the same pentacyclopentadecane.
mers (i.e., molecules having the same constitution) in a
In the synthesis of l a , b palladium bis(acety1acetosample are sufficient for determining the ee,''-'] even in the
nate) Pd(acac), or palladium bis(dibenzy1ideneacetone)
absence of an enantiomerically pure standard. Procedures
Pd(dba)_,is favored as palladium component of the catafor determining the ee based on this principle appear atlyst. Both phosphanes (PEt3, PiPr3, PPh3) as well as phostractive, but have not to our knowledge been developed so
phites (triisopropyl phosphite, tris(o-tolyl) phosphite) are
We discuss here one possible way of determining the
suitable as phosphorus ligands. As third component a
ee by the use of this principle, which may be applied to a
carboxylic acid is required whose pK, value lies between 3
wide variety of compounds.
and 5. This carboxylic acid must be present in at least the
When a mixture of enantiomeric molecules C(abcd)
same molar amount as the starting cyclopentadiene; cata(containing, e.g., only one stereogenic atom) in a n unlytic amounts of carboxylic acid are not sufficient for the
known ratio [R],/[S], is reacted with a bifunctional, achiral
formation of the trimers l a , b. The carboxylic acids emreagent
F, diastereomers are expected, viz., an achiral meso
ployed were, e.g., acetic acid, monochloroacetic acid, benspecies m and an enantiomericpair of chiral species e . The
zoic acid, and pivalic acid. Too strongly acidic acids, e.g.
species m and e may be distinguishable, e.g., by NMR
trichloroacetic acid, lead to the formation of polycyclopenspectro~copy,"~and from the ratio r=[m]/[e]. [R]o/[S]ocan
tadiene. Remarkably, the catalyst system presented here is
be worked out in prin~ip1e.l~'
However, r may be affected
capable of almost completely suppressing formation of the
appreciably by diastereoselectivity in the formation of m
Diels-Alder byproduct, dicyclopentadiene, even at reacand e . This diastereoselectivity may be kinetic or thermotion temperatures of 100 to 130°C.
dynamic in origin ; the experimental distinction between
The mechanism of the reaction is so far unclear. The
these two contributions is laborious.[']
reaction strongly depends on the solvent used, thus pointIf m and e are formed reversibly, then only thermodying to an ionic mechanism. A simple thermal [2+2]-cynamic diastereoselectivity is possible, and its extent is eascloaddition can be ruled out, since comparative experiily determined by analysis of the diastereomer ratio arising
ments without the bifunctional catalyst led only to the
in the reaction of racernic C(abcd) with F. The thermodyknown Diels-Alder products. Also, when either the pallanamic diastereoselectivity is defined by d = ([ m]/[e])racema,e.
dium complex o r the acid alone is used as catalyst no
The condition of reversibility is met if F is a kinetically
trimer l a , b is formed.
labile metal ion M11+i81
or a metal complex with at least two
labile ligands. Metal ions can serve as templates to hold
coordinating substrates at a close distance and, at the same
In a typical reaction 0.65 mmol Pd(acac), and 1.95 mmol PPh3 were distime, as transmitters for electronic effects, as required for
solved in 25 mL acetonitrile and treated with 9.9 g (0.15 mol) cyclopentadiastereomeric interaction. If r is to be determined by
diene and 18 g (0.3 mol) acetic acid. Yield after 4 h at 100°C and subsequent
work-up 7 g (70%) la, b.
NMR, then the use of diamagnetic metal ions is indicated.[']
Received: October 19, 1984;
supplemented: January 14, 1985 [ Z 1041 IE]
German version: Angew. Chem. 97 (1985) 326
CAS Registry numbers:
la, 95313-58-9; lb, 95313-59-0; Pd(acac),, 14024-61-4; PPh,, 603-35-0; cyclopentadiene. 542-92-7; acetic acid, 64-19-7.
Angew Chem. I n ! . Ed. Engl. 24 (1985) No. 4
Prof. Dr. W. Marty, Dr. M. L. Pasquier
lnstitut de chimie, Universite de NeuchPtel
Av. d e Bellevaux 5 I , CH-2000 Neuchltel (Switzerland)
This work was supported by the Swiss National Foundation for
Scientific Research and the Ciha-Geigy Juhilaumsstiftung.
0 VCH Verlagsgesellschaji mbH. D-694- Weinheim. 1985
0570-0833/85/0404-0315 $ 02.50/'0
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acid, bifunctional, palladium, homogeneous, trimerization, system, novem, cyclopentadienyl, catalyst
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