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Nonlinear Temperature Behavior of Product Ratios in Selection Processes.

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65-C for 48 h. The slurry was cooled and the solid isolated by centrifugation,
washed with dried methanol and dried under reduced pressure.
3 : The preparation was carried out in the same manner a s for 2 starting from
N,N-dimethylaminoethyldiphenylphosphaneoxide.
5 : A solution of [(OC),W(Ph,PCH2CH,NHMe,)](BF,) (0.75 g. 1.07 mmol) [prepared by reaction of [(OC),W(Ph,PCH,CH,NMe,)] (0.80 g, 1 38 mmol) in dry
degasseddiethylether(50 mL) withan85% solutionofHBF; Et,Oindiethylether
(0.36 g, 1.89 mmol)] in dry. degassed methanol (20 mL) was added to a slurry of 4
(0.10 g, 0.22 mmol) in dry. degassed methanol (20 mL) and the reaction stirred at
60 C for 48 h The slurry was cooled and the solid isolated by centrifugation.
washed with dried methanol and dried under reduced pressure.
Received: January 19, 1996 [287371E]
German version: A n g w . Client. 1996, 108, 1972- 1974
Keywords: complexes with phosphorus ligands intercalation
compounds - tungsten compounds * zeolites * zirconium compounds
7
[lI B. Heinrich, Y. Chen, J Hjortkjoer. J. Mol. Cutul. 1993. RU. 365.
[2] M. Lenarda, R. Ganzerla, L. Storaro. R. Zanoni. J. Mol. Cutul. 1993, 78,339.
[3] T. J. Pinnavaia, R. Raythatha, J. G.-S. Lee, L. J. Halloran, J. F. Hoffman, J.
Am. Chem. Soc. 1979, 101, 6891.
[4] F Farzdneh, T. J. Pinnavaia, Inorg. Chrm 1983. 22, 2216.
[5] V. L. K. Valli, H. Alper. Cltrnt. Muter. 1995, 7, 359.
[6] Y. Ding, D. J Jones, P. Maireles-Torres. J. Roziere, Chent. Muter. 1995, 7. 562.
[7] J. M. Troup. A. Clearfield, Inorg. CIiw. 1977. 16. 3311.
[8] G. L. Rosenthal. J. Caruso, Inorg. Clirm. 1992, 31, 144.
[9] G. L. Rosenthal, J. Caruso, J. Solid Stutr. Chem. 1991, 93, 128.
[lo] C. Ferragina, A. La GineStrd, M. A. Massucci, G. Mattogno, P. Patrono. P.
Giannoccaro, P. Cafxelli. M. Arfelli. J. Muter.. Chrin. 19955.461. and references therein.
[ I l l S. J. Mason, L. M. Bull, C. P Grey, S . J. Heyes. D. OHare, J. Muter. C h m .
1992. 2, 1189.
[12] C. F. Lee. M. E. Thompson, Inorg. Chem. 1991, 30, 4.
[I31 H . Benhamra, P. Barboux, A. Bouhaouss. F. Josien. J. Livage, J. M a r r r . Chern.
1991, /. 681.
[14] R. T. Smith, M. C. Baird, Inorg. Chint. Actu, 1982, 62. 135.
[15] D. J. MacLachldn, K. R. Morgan, J. PIiys. Chrm. 1990, 94, 7656.
[16] D. J. MacLachlan, K . R. Morgan, J Plzys. Chwt. 1992, 96, 3458.
[17] D. J. Darensbourg, C. J. Bischoff, Inorg. C/iem. 1993, 32. 47.
[18] A. Clearfield. R. M. Tindwd, J. btorg. Nircl. Chem. 1979. 41. 871.
[I91 M. Danjo. Y. Babd. M. Tsuhako, S. Yamaguchi. M. Hayama. H. Nariai, I.
Motooka. Bull. Chem. Soc. Jpn. 1995.68, 1607.
Nonlinear Temperature Behavior of Product
Ratios in Selection Processes**
Detlef Heller,* Helmut Buschrnann, and
Hans-Dieter Scharf
Dedicated to Professor Ivar Ugi
on the occasion of his 65th birthday
For selective reactions it has long been known that a logarithmic plot of the product ratio as a function of reciprocal temperature does not always display linear behavior.“ - 3 1 That the
[*] D r D. Heller
Max-Planck-Gesellscha ft
Arbeitsgruppe “Asymmetrische Katalyse” an der Universitit
Buchbinderstrdsse 5’6. D-18055 Rostock (Germany)
Fax: I n t . code +(381)4669324
e-mail: dhelle(irchemiel.uni-rostock.de
Dr. H. Buschmann
Grunenthal GmhH Aachen. Forschungszentrum
Zieglerstrasse 6, D-52078 Aachen (Germany)
Prof. Dr. H.-D. Scharf
lnstitut fur Organische Chemie der Technischen Hochschule
Professor-Pirlet-Strasse 1, D-52056 Aachen (Germany)
[**I The authors thank Prof. D. Haherland for stimulating discussions and
Prof. J. Ridd, London, for communicating his results. This work was supported by Prof. R. Selke, the Max-Planck-Gesellschdft, and the Fonds der
Chemischen Industrie.
1852
x>
VCH Verlugsgesellschufi mbH. 0-69451 Weinheirn. 1996
selectivity of a reaction need not fall regularly with decrease in
temperature is of considerable practical significance in efforts to
attain higher selectivity. In addition, interpretation of the temperature dependence can provide information on the mechanism of a reaction.[31 The temperature dependence has been
examined in detail in the case of the Paterno-Biichi reaction,
which led to the empirically derived isoinversion principle.[41
Accordingly, at the inversion point of two roughly linear regions, obtained by plotting the logarithm of the product ratios
[In(R/S)] versus 1/T, there is a change in dominance between
differences in activation enthalpy (AAH*) and activation entropy ( A A S *) for various selection levels. The difference in the
values of A A H * and A A S * before and after the point of inversion-in this case the inversion temperature IT;,,-leads
to the
isoinversion temperature 7; [Eq. (a)], which describes the selectivity of a reaction as a characteristic quantity. This is the socalled isoinversion principle.
aAAH*
=
T i .aAAS*
As an “abrupt” change of dominance between A A H * and
A A S * is rather unlikely, according to Ridd,[’I he interpreted the
experimentally determined nonlinear temperature dependence
of the logarithmic product ratios as a shift in the rate-determining step of the reaction with change in temperature. This alternative interpretation is based o n a simulation with empirical
energy levels. The shift in the rate-determining step has also
been invoked by Sharpless for the asymmetric olefin dihydroxylation with OsO, (in the presence of chiral bases).[31
Common to the two apparently contradictory viewpoints is
the consideration of the temperature dependence of the ratio of
the overall rate constants in terms of Eyring theory.[61The subsequent difference in free activation enthalpy AAG * resulting
from processes leading to selection is also the basis of the stereochemical structure model of Ugi and R ~ c h . [ ’ ~
The aim of the present work was to extend the previous examples and interpretations of the nonlinear temperature dependence in selection processes, and to trace this exclusively back to
the nonlinear change in the concentration ratio of the intermediate with the variation in temperature. This should be demonstrated with one of the best understood selection processes, catalytic asymmetric hydrogenation. According to Halpern[*] and
Brown:’] asymmetric catalytic hydrogenation with five-membered Rh chelate complexes proceeds as shown in Scheme I . All
subsequent considerations are based exclusively on two
diastereomeric intermediates, which are prepared with chiral
C,-symmetric hgands, for example, Kagan’s DIOP ligand
(Fig. I).[’’]
As shown in Scheme 1 , the diastereomeric substrate complexes Em, and Em,are formed in the first selection level in a preequilibrium. In a series of elementary steps--oxidative addition of
hydrogen, insertion, reductive elimination-these react at different rates in the second selection level to give the enantiomers.
Under normal conditions the rate of the oxidative addition is
recognized to be rate-determining.
The ratio of enantiomers is described by Equation (b).
Whereas a plot of In(R/S) against 1/T gives, in principle, a
‘mi
_
-
Em
straight line for established preequilibria (k,,, @ klmao r k _
kZmi< klmior k- l m i ) , for a nonestablished preequilibrium this
0570-0833i9613516-1852 $ 15.00 -t.25/0
Angru.. Chem. Int. Ed. Engl. 1996, 35. No. 16
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Equation (b). The temperature dependence of the ratio of the diastereomeric
substrate complexes is shown in the
k*?ma 1H21
lower part of Figure 3. Whereas the
O
i
curve is still linear at higher temperatures as expected, at lower temperaCH,
tures the curve deviates increasingly
(Em)
from linearity. Although all rate con07
i
stants become smaller with decreasing
temperature, the displacement of establishment of the preequilibrium becomes more pronounced with decreasing temperature.
O
i
Summation of the individual factors
from Equation (b) for the temperature
dependence shown in Figure 3 gives
the temperature dependence of the
diastereomeric
substrate
(R)product
enantiomer ratio for the overall reaccomplexes
tion, as shown in Figure 2. When FigSchcinc I . t u i n p l e o f a n asymmetric hydrogenation catalyzed by a rhodium complex. The (H)amino acid I S formed
ure 3 i s considered from this aspect, it
in exce\\. (E,",and E,,, are the major and minor substrate complexes, respectively: X , : rateconstants: Xf,,[H,] = X,,,:
i s apparent that at higher temperatures
A L [ H ? l = /\?cm,)
the oxidative addition (second selection level) i s the major contribution to the enantiomer ratio. In
contrast, at very low temperatures the selectivity results predominantly from the ratio of the diastereomeric substrate comCH
plexes (first selection level). This increasing dominance of the
first selection level is caused exclusively by the increasing deviam
tion, with decreasing temperature, from linearity of the temperH
PPh,
I
ature dependence of the ratio of the diastereomer concentraPPh,
tions (Em,/EmA),
which i s the real cause for the nonlinear
(R,R)-DIOP la
Phenyl-6-glup-OH l b
temperature dependence of the enantiomer ratio. Thus. both
second selection level
first selection level
Re attack
Fig I C'hirJl Ii$ands for asymmetric hydrogenation. DlOP
phosphinomcth~l)-ll.7-dimethyll.3-dioxolane.
=
4.5-bis(diphenyl6T
1127
can no longer be the case because of the additive coupling of the
rate constants. As the ratio of the rate constants kzmi/kzm,
leads
in principle to a linear temperature dependence, the experimentally observed nonlinearity must depend on a change in the
concentration ratio of the diastereomeric substrate complexes
with temperature. This will be explained with an example.
lcihlc I Value, lor A H * [kcalmol-']and A S * [ c a l m o l - ' K - ' ] for thecalculation
o f thc irate u i i u t : i i i t \ according to Equation ( b )
IT
4
+13
3s
1
3'4
33
IRI
InI s ' 3.2
3.1
3
2.5
At1 '
AS'
h
(J
- 17 0
4.9
-24.6
13.0
- 12.Y
I.<. ?
- 17.9
8.5
-27.0
13.5
-24.0
Table 1 contains A H * and A S * values for the determination of
rate constants according to Equation (b). The rateconstants for
the preequilibrium are those found for asymmetric hydrogenation.l8I Because the thermodynamically less stable minor substrate complex reacts at a higher rate to give the enantiomer
found in excess. as shown by Halpern in terms of the major/minor concept.Ix1 only the values for calculation of the rate coni
kzm,,have been simustants of the oxidative addition, k Z m and
lated. The temperature dependence of the product ratio ( R I S )is
shown in Figure 2. In the temperature range from roughly
-25 C to about + 130 C a characteristic maximum can be
seen.
The upper part of Figure 3 shows the expected linearity in the
temperature dependence of the ratio of the rate constants for the
oxidative addition as one of the factors on the left-hand side of
3
3.5
T-I
-
4
103-
Fig. 2. Temperature dependence of the enantiomer ratio (calcula~edwith the constants from Table 1).
1127
lo,
'
-TIT
4
113
T-1
. 103
-23
t
-
Fig 3 . Temperature dependence of the individual Factors from Equation (b) [ e:
A = (/i2m,:kz,",,); 0 : A = ( R : S ) :0 : A = (Em,,Em,)].
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~
sides of the maximum can, in principle, be explained as resulting
from the dominance of different selection levels in different temperature ranges. This is an essentially empirical statement of the
inversion prin~iple.'~]
We will now discuss the nonlinear temperature dependence of
the concentration ratio of the intermediates as the cause for the
nonlinear behavior of the product ratio in a selection process. In
principle, for the asymmetric hydrogenation with C,-symmetric
ligands as an example of a selection process, this behavior can
be traced back to two possible c a ~ s e s : [ ' ' 1~) displaced (intermolecular) preequilibria and 2) intramolecular equilibria.
The displacement in the establishment of a preequilibrium,
the position of which is temperature dependent. means that the
stationary concentration of the affected substrate comdex will
become smaller. Coupling of the diastereomeric substrate complexes through their the common substrate leads to a change in
the ratio of the intermediates (see also ref. [12]). The increasing
displacement in reaching the preequilibrium through increasingly faster subsequent reactions of the intermediate ultimately
results in other steps becoming rate-determining; this corresponds to the "transition region" described by Ridd.[51 The
nonlinear temperature dependence of the logarithmic product
ratio in this transition region is based on a change in the ratedetermining step. In our opinion this is caused by the nonlinear
shift of the concentration ratio of the intermediate as a function
of temperature.
A second Dossible cause is the intramolecular exchange
- between diastereomeric substrate complexes, as described for fivemembered chelate rings['3. and recently quantified for sevenmembered chelate rings." 51 In principle, even when all equilibria
are established, this leads to a nonlinear temperature dependence of the ratio of the diastereomeric substrate complexes (for
a derivation, see ref. [16]). This is particularly valid when the
intramolecular exchange processes are more dominant than the
intermolecular equilibria.
Thus. we have shown that the arguments in the discussion[4.
on the interpretation of the nonlinear temperature dependence
of logarithmic product ratios are not contradictory. Both interpretations are possible within defined limits. The cause for the
experimentally observed dependence can be reduced to the concentration ratio of two intermediates that changes with temperature in nonlinear fashion; further reaction of these two intermediates then leads to selective product formation. The causes
of the nonlinear changes in the ratio of intermediates are then
displaced intermolecular preequilibria and intramoiecular exchange processes of substrate complexes that appear as intermediates.
Received: January 8. 1996
Revised version: March 26. 1996 [Z87061E]
German version: Angeii'. Chem. 1996, 108. 1964- 1967
Keywords: asymmetric hydrogenations * isoinversion principle
selection processes
-
[I] H. Pracejus. Liebigs Ann. Chrm. 1960, 634. 9-22.
121 E.Anders. E. Ruch. I. Ugi. Angew. Cheni. 1973, NS, 16-20: Angeiv. Chem. In/.
Ed. €ngi 1973, 12.25-29.
[3] T. Gobel, K. B. Sharpless, Angeu.. Cliem. 1993, 105, 1417-1418; Angeir. Chiw.
In/.Ed Engl. 1993.32. 1329-1330.
[4] H. Buschmann, H.-D. Scharf. N. Hoffmann. P. Esser. A/zgew. Chem. 1991. 103.
480-518; Angrw. Cheni. In!. Ed. Engl. 1991, 30. 477-515.
[S] K. J. Hale, J. H. Ridd. J Chem. Soc. Perkin2 1995, 1601 1605.
[6] S. Glasstone, K. J. Laidler, H. Eyring. The TIieurJ o/Ru!e Processes. McGrawHill. New York. 1941.
I71 1. Ugi. 2. Nulurforsch B 1965. 20, 405-409.
[81 C . R. Landis. J. Halpern. J Am Cl?em. Sor.. 1987. 109. 1746-1754.
[91 J. M. Brown. P. A Chaloner i n Homogenmu.y Cuiulrsis with Me/ul-Phosplzine
ComplrJ.ws(Ed.: L. H. Pignolet). Plenum, New York. 1983. pp. 137-165.
1854
(> VCH ~ ~ r l u g \ g e ~ r l l s ~ mhH
h u / r D 69451 Wrinherm 1996
[lo] H. B. Kayan. T. P. Dang. J Am. Chem. Soc. 1972, 94. 6429- 6433.
1111 R. Selke. J Oi,qunomet. Chem. 1989, 370, 241 -248.
1121 D. Heller. S . Borns. W Baumann, R. Selke, Chen?. Ber. 1996. f29. 85-89.
11.31 H. Bircher. B. R. Bender, W. von Philipsborn, M a p Reson. Chem. 1993. 31.
293-298.
[14] J. A. Ramsden, T. D. W. Claridge, J. M. Brown. J. Chcvv. Soc. Chem. Commun.
1995, 2469 - 2471.
[15] R. K;idyrov. T. Freier. D. Heller, M. Michalik, R Selke. J Cheni. Sot. Chtm.
Commrm. 1995, 1745- 1746.
[16] D. Heller. R Thede. D. Haberland, unpublished results.
1171 By the use of C,-symmetrical ligands (an example is shown in Fig. 1 ( I b) [I 11)
formation of individual enantiomers can be the result of two independent
processes. because four substrate complexes are possible in principle. This
means that the logarithmic product ratio changes with temperature in principle
in nonlinear fashion.
Synthesis of New Dialkylmagnesium Compounds
by Living Transfer Ethylene Oligo- and Polymerization with Lanthanocene Catalysts
Jean-Franqois Pelletier, Andre Mortreux,* Xavier
Olonde, and Karel Bujadoux
Dedicated to the memory of Professor Francis Petit
Considerable interest has been devoted to oligomerization
and polymerization of ethylene on transition metal catalysts.
The aim of these reactions is to produce higher olefins (Alfen,
Alphabutol, SHOP processes) or polymers of higher molecular
weight (Ziegler-Natta catalysis). Such reactions and those with
the relatively recently discovered metallocene-based catalysts
produce linear, vinyl-terminated chains, which can be transformed by the use of stoichiometric amounts of zirconocene
compounds into functionalized compounds.['' This kind of
functionalized oligomers, however, can be obtained by anionic
polymerization of ethylene with n-butyllithium followed by electrophilic substitution of the resulting living oligomer.[21In contrast, organomagnesium compounds have been synthesized
from olefins by using zirconocene-based catalysts and dialkylmagnesium compounds or Grignard reagents as core act ant^,[^^
and zirconium tetrachloride has been used as catalyst for the
synthesis of dialkylmagnesium compounds from MgH, and aolefins, a process, which could be followed by ethylene addition.
but only under severe condition^.'^]
We report herein that the ethylene insertion into a Mg-C
bond can be catalyzed under very mild conditions by an alkyl
chain transfer through chain growth polymerization on a lanthanocene-based catalyst.[51 This new reaction is a useful
method for the synthesis of compounds of the type P-Mg-P
(P = alkyl chain), in which, depending on the reaction parameters, P or P' can contain between four and 200 C atoms, and a
narrow distribution of products is obtained [Eq. (a)].
BuMgEt
+ (n + m)CH2=CH2
-
IC~~S~CI~L~(OE~~I~I
P-Mg-P'
[*] Prof. Dr. A. Mortreux. Dr. J.-F. Pelletier
Laboratoire de Catalyse Heterogene et Homogine
Ecole Nationale Suptrieure de Chimie de LiIfe
URA CNRS 402, BP 108
F-59652 Villeneuve d'Ascq (France)
pax' Int. code +2043-6585
Dr. X . Olonde, Dr. K . Bujadoux
ECP Enichem Polymeres France, Centre de recherches. BP 2 F-62670 Mazingarbe (France)
0570-0833~96/3516-1854
$ 15 00+ 2510
Angeu Clzem
Im Ed Engl 1996, 35 N o 16
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