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High LaIII Affinity of a Bis(spirobenzopyran) Azacrown Ether and Photoinduced Switching of its Ion Selectivity between Multivalent and Monovalent Metal Ions.

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103.9 (terminal allylic), 90.1 (bridgehead), 63.9 (NMe), 63.2 (CH,), 47.6 (ZrMe,);
elemental analysis calcd for C,8H3,N,Zr,: C 59.12, H 8.27, N 7.66; found: C 59.43,
H 8.38, N 7.60; LRMS (EI): miicalcd: 364; found: 364.
4: Complex 2 (103 mg, 0.254 mmol) was dissolved in 10 mL T HF and cooled to
- 30 "C. Benzylmagnesiumchloride (1 M in ether, 481 mL, 0.481 mmol) was added,
and the solution stirred at room temperature for 2 h. The solvents were removed in
vacuo. Complex 4 was recovered by extraction of the residue with toluene. The
volatile materials were removed to give 110 mg (88 %) of an orange solid. Analytically pure crystals of 4 can be obtained by vapor diffusion of pentane into a toluene
solution of this solid at - 30 'C. H NMR (C,D,): 6 = 7.27 (t, J = 7.7 Hz, 4 H, Ar),
7.12 (t. J =7.7 Hz, 4H, Ar). 6.90 (t. J = 7.2 Hz, 2H,Ar), 5.14 (dd, J =7.4 Hz. 2H.
central allylic), 3.80 (d, J = 7 . 3 Hz, 2H. terminal allylic), 3.78 (d, J = 7 . 3 Hz, 2H.
terminal allylic), 2.85 (br s, 4H, bridgehead), 2.05 (s, 6H, NMe). 1.95 (m. 4H,
CN,Ph), 1.72 (s, 8H, CH,); "C{'H} NMR (C,D,): 6 = 155.8(C,,,,), 128.9(centraI
allylic), 128.0 (Ar), 125.7 (Ar), 119.4 (CDa,J,83.8 (terminal allylic). 66.4 (bridgehead), 58.6 (CH,Ph), 40.2 (NMe), 39.5 (CH,); elemental analysis calcd for
C,,H,,N,Zr: C 69.58, H 7.40, N 5.41; found. C 69.56, H 7 60, N 5.21.
Polymerization of C,H, by 2 and MAO. A Schlenk flask was charged with 2
(5.3 mg, 13 mmol)and 8 mL toluene and placed under 1 atm ethylene. MA0 (Akzo,
type 4; 3.4 mL, 13 mmol) was added over 1 min at room temperature. The yellow
solution immediately turned dark orange, then blue and violet. The color vanished
within 15-20 min. The solution was stirred under 1 atm ethylene for 45 min, and
then the polymerization was stopped by careful addition of an acidified methanol
solution ( 5 % HCI). The mixture was filtered, and the polymer thoroughly dried in
vacuo. Yield: 102 mg (17 kgmol-'h-I). Similar conditions were used for the control experiment with Cp,ZrCl, (240 kgmol-'h-').
Received: May 20, 1997 [Z10450IE]
German version: Angen. Chem. 1997, 109,2555-2558
Keywords: polymers
sandwich complexes
[I] J. P. Collman, L. S. Hegedus, J. R. Norton, R. G. Finke, Principles and Applications of Organotransition Metal Chemistry, University Science Books, Mill
Valley, 1987.
[2] H. H. Brintzinger, D. Fischer, R. Mulhaupt, B. Rieger, R. M. Waymouth,
Angew. Chem. 1995, 107, 1255; Angen. Chem. Int. Ed. Engl. 1995,34, 1143.
[3] G. Wilke, B. Bogdanovic, P. Hardt, P. Heimbach, W. Keim, M. Kroner, W.
Oberkirch, K. Tanaka, E. Steinriicke, D. Walter, H. Zimmermann, Angew.
Chem. 1966, 78, 157; Angew. Chem. Int. Ed. Engl. 1966.5, 151
[4] Comprehensive OrganometallicChemistrJ; II, Vol. 12(Eds.:E. W. Abel, F. G. A.
Stone, G. Wilkinson), Elsevier, 1995.
[5] J. Blumel, N. Hertkorn, B. Kanellakopulos, F.H. Kohler, J. Lachmann, G.
Miiller, F. E. Wagner, Organometallics 1993, 12, 3896.
[6] K. J. Shea, Tetrahedron 1980, 30, 1683.
[7] G L Buchanan, Chem. Soc. Rev. 1974,3,41.
[S] G. Kobrich, Angew. Chem. 1973, 85, 494; Angew. Chem. I ~ IEd.
. Engl. 1973,
[9] A Ladenburg, Justus Liebigs Ann Chem. 1888, 217, 118.
[lo] Deprotonation must be performed at low temperature to prevent decomposition of the product to an unidentified mixture of compounds.
[ll] SIR92: A. Altomare, M Cascarano, C. Giacovazzo. A. Guagliardi, J: Appl.
Cryst. 1993, 26, 343.
[I21 DIRDIF92: P. T. Beurskens, G. Admiraal, G. Beurskens. W. P. Bosman, S.
Garcia-Granda, R. 0. Gould, J. M. M. Smits, C. Smykalla. The DIRDIF Program System, Technical Report ofthe Crystallography Laboratory, University
of Nijmegen, The Netherlands.
1131 X-ray quality crystals of 2 were obtained by slow diffusion of pentane into a
solution of the complex in toluene at -30°C. The structure was solved by
direct methods with a full matrix least-squares refinement. Details of the X-ray
structures of 3 and 4 will be reported in a full paper. Crystal data for 2 :
C,,H,,C,,N,Zr. Orange plate-like crystals (0.08 x 0.14 x 0.35 mm), monoclinic, space group P2Jn (no 14), a = 7.0931(2),h = 18.2744(2),c = 12.8139(3) A;
B = 85.777(1)", V = 1652.53(5)A3. Number of observed reflections
[I>3.0Ou(I)] 2193; 190 variables; R = 0.028, R, = 0.035, R,,,= 0.042,
GOF = 1.33. Crystallographic data (excluding structure factors) for the structure reported in this paper have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication no. CCDC-100489. Copies
of the data can be obtained free of charge on application to The Director,
CCDC, 12Union Road, Cambridge CBZlEZ, U K (Fax: Int. code
+ (1223)336-033; e-mail:
[14] K. Prout, T. S. Cameron, R. A. Forder, S. R. Critchley, B. Denton, G. V. Rees,
Acta Crystallogr. Sect. B 1974, 30, 2290.
[15] W. E. Hunter, D. C. Hrncir, R. V. Bynum, R. A. Penttila, J. L. Atwood,
Organometallics 1983. 2. 750.
[16] Preliminary measurements showed that the polyethylene exhibits a relatively
high molecular weight but a rather broad polydispersity ( M , = 628045;
M , = 14267). We are grateful to Drs. Timothy Wenzel and Thomas Peterson.
u n io n Carbide Co., for arranging to have these measurements made.
0 WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1997
High La"' Affinity of a Bis(spirobenz0pyran)
Azacrown Ether and Photoinduced Switching
of its Ion Selectivity between Multivalent and
Monovalent Metal Ions**
Keiichi Kimura,* Tomohito Utsumi, Takashi Teranishi,
Masaaki Yokoyama, Hidefumi Sakamoto, Masanori
Okamoto, Ryuichi Arakawa, Hiroshi Moriguchi, and
Yoko Miyaji
The photochromicity of spirobenzopyran derivatives is due
to photoisomerization between their electrically neutral spiropyran and zwitterionic merocyanine forms.['] The photochromism can often be used for controlling physical properties.['] We are interested in macrocyclic ligands that can switch
their metal ion complexing ability and/or their ion selectivity
photochemically, as well as their application in materials science
and analytical chemistry. We therefore designed 1,3,3-trimethylindolino-6-nitrobenzopyrylospiranderivatives with a
crown ether moiety at the 8'-position, in which the phenolate
oxygen atom of the merocyanine form plays an important role
in metal ion complexation by forming a six-membered ring
chelate with a nitrogen atom of the azacrown ether.13' The
spirobenzopyran azacrown ethers can undergo photochemical
switching upon complexing monovalent metal ions, and have
been successfully applied in photoresponsive ion-conducting
Recently the crown ether derivative 1, which has two
spirobenzopyran moieties, was designed for photocontrol of the
In our studies, we found
complexation of divalent metal
that, even in the dark, 1 binds multivalent metal ions much more
strongly than its corresponding parent azacrown ether 2
(Scheme I). Here we report the remarkably high affinity of 1 for
La3+ and the photochemical switching of its ion selectivity between trivalent and monovalent metal ions.
Absorption spectra of solutions containing equimolar
amounts of 1 and a metal ion in acetonitrile recorded in the dark
showed a significant peak between 500 and 600 nm, which were
assigned to the merocyanine form of the photochromic moiety;
isomerization into this form was induced by complexation of the
cation by the crown ether moiety. In general, the merocyanine
absorption was much more intense for mulitivalent metal ions
such as Ca2+ and La3+ than for monovalent ions such as Na+
and K + . This suggests a higher affinity of 1 for multivalent
metal ions than for monovalent ones. Clear evidence for this was
given by ESI mass spectrometry. Figure 1 shows a mass spectrum of 1 and 2 in acetonitrile in the presence of the nitrates of
Li+, Na+, K + , Mg2+, Ca2+, Cd2+, Pb", La3+, and Eu3+.
With 2, medium-intensity peaks were observed for the Na+ and
K + complexes and a very small peak was seen for the Ca2+
[*I Prof. Dr. K. Kimura, T. Utsumi, T. Teranishi, Prof. Dr. M. Yokoyama
Chemical Process Engineering, Faculty of Engineering
Osaka University
Yamada-oka, Suita, Osaka 565 (Japan)
Fax: Int. code +(6)879-7935
e-mail: kimura(
Dr. H. Sakamoto
Department of Applied Chemistry, Faculty of Systems Engineering
Wakayama University (Japan)
M. Okamoto, Prof. Dr. R. Arakawa, H. Moriguchi, Y. Miyaji
Department of Applied Chemistry, Faculty of Engineering
Osaka University (Japan)
I**] This work was supported by a Grant-in-Aid for Scientific Research from
the Japanese Ministry of Education, Science, Sports, and Culture. Financial
support from Nagase Science and Technology Foundation is also acknowledged.
0570-0833/97/3622-2452$17.50+ .50/0
Angen,. Chem. Int. Ed. Engl. 1997.36, No. 22
+ Mm
LO w 0 J
Scheme 1. Complexation of metal ions by 1 and 2
[l+La +NO,f'(565)
[l+Cdff (521)
[l+Ca]'+ (485)\ \
[2+Caf+ (151)
I' ,
[1+Pbj2' (568.5)
Figure 2. 139LaNMR spectra of a solution of La(NO,), in CD,CN (a) and in the
presence of 1 (b) and 2 (c) in the dark. c[La(NO,),] = 2 x lo-', c(1) = 1.5 x lo-',
42) = 3 x lo-' mol dm-3.
, / / [ l + E ~ + N 0 , 1 ~ + (571.5)
1 1 ,
mlzFigure 1. Mass spectra of solutions of 1 (a) and 2 (b) in acetonitrile in the presence
ofthenitrates of Li', N a+ , K', Mgz+, Cazi, Cd2+,Pb", La", and Eu3+ in the
dark. c(1) = 42) = c(meta1 nitrate) =1 x
complex. There was no indication of complexation of other
metal ions, especially trivalent ions, by 2. This observation is in
good accord with the general ion selectivity of the diaza-18crown-6 ring.[61Surprisingly, no significant peaks for the complexes of the monovalent metal ions with 1 were seen. Instead,
medium-intensity peaks were observed for the complexes of divalent ions Ca2+,CdZ+,and PbZ+.Most interestingly, the most
intense peak corresponds to a complex of 1with the trivalent ion
Thus, with a preference for mulitivalent rather than monovalent metaI ions, the complexation properties of 1differ greatly
from those of its parent crown ether. This suggests a strong ionic
interaction of the phenolate anion of the merocyanine moiety
with a metal ion in the crown ether component. Since the small
cations Mg2+ and Eu3' give no peak and a relatively small
peak, respectively, for the complex with 1, a size fit of the crown
ether moiety to the metal ion is also crucial for formation of
stable complexes with 1.
'39La NMR spectroscopy provided important information
on the strong interaction between La3+ and the phenolate anion
in the complex l-La3+ (Figure 2). A 'HNMR experiment indiAngew. Chem Int. Ed. Engl. 1997,36, No. 22
cated that both of the spirobenzopyran moieties in the l-La3'
complex are isomerized to the corresponding merocyanine
even in the dark. Addition of 2 in high concentration to
a solution of La3+ in acetonitrile led to broadening and a downfield shift of the '39La NMR signal. This means that La3+ is
complexed by the crown ether by an ion - dipole interaction, and
that the complex is quite unsymmetrical. In contrast, addition of
1 gave a sharper peak and an upfield shift, indicating that the
phenolate oxygen atoms of the merocyanine form of 1 act as
axial ligands that interact strongly with an La3+ ion in the
crown ether moiety. Since the La3+ complex of 1gives a single
peak in the mass spectrum, assigned to [1-La(NO3)IZ+,the positive charge of La3+ in the crown ether moiety may be balanced
not only by two phenolate anions but also by a nitrate anion.
The peak sharpness also suggests that the asymmetry of the
2-La3+ complex is alleviated by axial interaction with the phenolate oxygen atoms. Presumably, such strong ionic or coordinative interactions with the phenolate anions is responsible for
the remarkable selectivity of 1 for multivalent metal ions, especially La3+,over monovalent ones.
Since 1 and 2 differ so greatly in their selectivity for monoand multivalent metal ions, photoisomerization of the merocyanine moiety of 1 back to its electrically neutral spiropyran
form should switch the ion selectivity from multivalent to
monovalent metal ions. We attempted to observe photoinduced
ion selectivity switching of 1by ESI-MS with an on-line photoirradiation apparatus.['] As already mentioned, 1 has a much
higher affinity for multivalent metal ions than for monovalent
ones. However, with 100 molar equivalents of K + and one molar equivalent of La3+, the ion peak of 1-K+ complex can be
seen together with that of l-La3+ (Figure 3a). Mass spectra
were recorded immediately after irradiation of the solution of 1
in acetonitrile with visible light (> 500 nm) in a glass capillary in
the ESI interface. The peak ratio l-La3+: 1-K+was significantly
lower after photoirradiation (Figure 3b). Clearly the ion selectivity of 1 can be switched from La3+ to K + . When irradiation
was ended, the high La3+ selectivity of 1 was restored.
Thus, crowned bis(spirobenz0pyran) 1 has realized the extremely high affinity for La3+ by the powerful interaction with
0 WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1997
11+KJf (969)
1 ;i
mizFigure 3. Mass spectra of a solution of 1in acetonitrile containing La3+ and K' in
the dark (a) and after irradiation wlth visible light (2.b 500 nm) for 20 min (b).
~ ( 1 =1
) x lo-', c[La(NO,),I = I x lo-', c[KNO,]: 1 x
two phenolate anions of its merocyanine moiety and the visiblelight-induced selectivity switching from La3 to K +.
Received: May 14, 1997 [Z104361E]
German version: Angew. Chem. 1997,105, 2558-2560
Keywords: crown compounds host -guest chemistry
thanum selectivity control - spiro compounds
[l] R. C. Bertelson, in Phorochromism(Ed.: G. H. Brown), Wiley Interscience, New
York, 1971, pp.45-431.
121 J. Sunamoto, K. Iwamoto, Y Mohn, T. Korninato, J. A m . Chem. SOC.1982,104,
5502-5504; J. D, Winkler, K. Deshayes, B. Shao, ibid. 1989, fff, 769-770;
S. Kato, M. Aizawa, S . Suzuki, J. Membr. Sci. 1976, f, 289-300; J. Anzai, A.
Ueno, T. Osa, J. Chem. Soc. Chem. Commun. 1984,688-689; M. Irie, A. Menju,
K. Hayashi, Nippon Kagaku Kaishi 1984, 227-232; 0. Ryba, J. Petranek,
Makromol. Chem. Rapid Commun 1988,9, 125-128; M. h e , T. lwayanagi, Y.
Taniguchi, Macromolecules 1985, 18, 2418-2422; F. Ciardelli, D. Fabbri, 0.
Pieroni, A. Fissi, J Am. Chem. SOC.1989, f l f , 3470-3472.
131 a) K. Kimura, T. Yamashita, M. Yokoyama, J. Chem. SOC.
Perkin Trans. 2 1992,
613-619; b) for similar spirobenzopyran crown ether derivatives, see M. Inouye,
M. Ueno, T. Kitao, K Tsuchiya, J. Am. Chem. Sor. 1990, l f 2 , 8977-8979;
S. Akabori, Y. Fujimine, 59th National Meeting of the Chemical Societj of Japan,
1990, abstract 1E315.
[4] K. Kimura, T. Yamashita, M. Yokoyama, J Phys. Chem. 1992,96, 5614-5617.
[5] K. Kimura, T. Teranishi, M. Yokoyama, Supramol. Chem. 1996, 7, 1 I - 13.
[6] R. M. Izatt, K. Pawlak, J. S. Bradshaw, R. L.Bruening, Chem. Rev. 1991, 51,
[7] The sample solution was sprayed with a flow rate of 0.15 crn3h-' from the tip
of a quartz glass capillary needle fo which a voltage 3.5 kV higher than that of
the counterelectrode was applied.
Ion-Exchange Resins for Combinatorial
Synthesis: 2,4-Pyrrolidinediones by
Dieckmann Condensation**
Bheernashankar A. Kulkarni and Arasu Ganesan*
Dedicated to Y: R. Mamdapur
on the occasion ofhis 60th birfhday
Combinatorial organic synthesis has tremendous potential in
areas which benefit from high-throughput screening of com[*] Dr. A. Ganesan, Dr. B. A. Kulkarni
Institute of Molecular and Cell Biology
National University of Singapore
15 Lower Kent Ridge Road, 1 19076 (Singapore)
Fax: Int code +779-1117
[**I This work was supported by funds from the National Science and Technology
Board, Singapore.
0 WILEY-VCH Verlag GmbH, D-69451 Welnheim,
pounds for a desired property. Thus far, the emphasis has been
on drug discovery,"] although applications['] such as molecular
recognition, catalysis, and materials science are likely to increase in importance. It is now clear that few, if any, organic
reactions are incompatible with library synthesis. However,
as most transformations are not quantitative, the major challenge lies in purifying products from unchanged starting materials, undesired by-products, as well as catalysts and other
Current library-purification methods rely on phase separation.131In the solid-phase procedure, the compound is covalently attached to a resin, while reagents are removed by simpIe
filtration. This enables the use of large excesses of reagent to
drive reactions forward. However, solid-phase synthesis has a
number of limitations, including the need for translation of
reaction conditions optimized in solution. Recently, solutionphase methods for library generation have gained in popularity,
accompanied by protocols for achieving phase separation such
scavenger^)'^ and
as acid- base e ~ t r a c t i o n ) ~resin-bound
fluorous three-phase partitioning.[6] Here we report a combinatorial synthesis in which an ion-exchange resin serves as a
reagent and a purification agent.
We were interested in a modular synthesis of 2,4-pyrrolidinediones (tetramic acids) as a scaffold for novel biologically active
compounds. These heterocycles were envisaged to arise by the
following sequence (Scheme 1): 1) reductive alkylation['' of an
Scheme 1. Combinatorial synthesis of 2,4-pyrrolidinediones; DCC = dicyclohexyl
carbodiirnide, HOBt = I-hydroxy 1H-benzotriazole hydrate.
a-amino acid ester, 2) acylation of product 1 with a substituted
acetic acid, and 3 ) Dieckrnann condensation['] of amide ester 2
to yield 2,4-pyrrolidinedione 3.The final products are thus assembled from three building blocks (amino acids, aldehydes,
carboxylic acids) that are available with a high degree of diversity.
First we performed a model study: N-benzylglycine ethyl
ester was coup1ed''l with cyanoacetic acid to give amide 2a
(R' = H, R2 = Ph, R3 = CN). The desired Dieckmann condensation"'] occurred in 70-80°/0 yield with various bases." l1
We also found that Amberlyst A-26 resin (OH- form) promotes
the cyclization. The simplicity of handling makes this the
reagent of choice, and we believe this to be the first use of an
ion-exchange resin for this venerable reaction." 21
The pyrrolidinedione remains tightly bound to the resin until
it is released by acid treatment (Scheme 2) .[I3] Only successfully
cyclized material is resin-bound, whereas other components are
washed away. This represents a new paradigm for solutionphase library purification. Previous applications of ion-exchange resins in combinatorial synthesis emphasized their use as
activating agents"'] or scavengers.[' I 6 ] In this respect, Our
0570-0833/97/3622-2454$ 17.50+.50/0
Angew. Chem. Int. Ed. Engl. 1997, 36, No. 22
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ion, selectivity, multivalent, high, laiii, ions, spirobenzopyran, azacrown, switching, monovalent, photoinduced, ethers, metali, bis, affinity
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