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Deuterium-Induced Phase Transition of an Organic MetalЧAn Unusual Isotope Effect.

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no side reactions, and the reaction is complete after 48 h. It
was followed by IR spectroscopy by observing the complete
disappearance of the azido absorption band at ? =
21 17 cm- ' (KBr windows). At the end the resin-bound 8 and
9 were treated with hydrazine hydrate in methanol (1 :7) for
about 6 h,ISd-f, ' 7 . 181 which deacetylated all sugar residues
to 10 and 11. The cleavage of the synthesized glycopeptides
was achieved in 2 h with 95 YOaqueous trifluoroacetic acid
(TFA). The N-acetyl glycopeptide amides 12 and 13 were
then purified by RP-HPLC and were identical with those
prepared along other routes.['g1
Alternatively, the new procedure can be used in a multiplecolumn or a fully automatic peptide synthesizer." 7 *'] The
multiple column process is preferable when several peptide
sequences with few sugar residues are required. For example,
besides others the glycopeptides 12 and 13 were synthesized['.
and could be obtained pure in high yields of 77 %
and 72 o/o.r211 In a fully automatic peptide synthesizer the
complex structure of 14 with five vicinal sugar residues was
synthesized. In this case the peptide synthesis was observed
photometrically and could be controlled by the disappearance of the yellow color of the Dbht-OH salt.~"~201
In the
synthesis of the penta-glycosylated octapeptide, the reduction
of the azido groups and the deacetylation of the carbohydrates also was achieved without difficulty, and 14 was isolated pure in yields of 40%.[211The 'H NMR, FAB-MS, and
amino acid analysis data are in accord with the structure.L2']
This example serves to illustrate the power of the new
method. Peptides 12, 13, and also 14 are partial structures of
the repeating unit of human intestinal m ~ c i n , 'and
~ ~ ]should
be tested for the specificity of the glycosyl transferases.
Received: January 25, 1992 [Z5150IE]
German version: Angew. Chem. 1992, 104, 881
3.5 Hz, 1 H; Fmoc-Ch,-b), 4.24 (m. 1H ; Thr-CHO), 4.15-3.98 (m, 4 H ;
Fmoc-CH,H5,2xH6),3.62(dd,3J(2,3)=11.0Hz,
I H ; H2), 1.72, 1.66
(2% 9 H ; 3 x COCH,), 1.13 (d, ' J = 6.5 Hz, 3 H ; Thr-CHy). FAB-MS: m;z
821.2 ( M fl) (calcd for C,,H,,F,N,O,,:
M , = 820.2). - 5: [a];* = +77.8
(c =1.0 in chloroform); m.p. 73°C; 'H NMR (400 MHz, CDCI,. 27°C.
TMS): b =7.78-7.29 (4m, 8 H ; arene H), 6.03 (d, 'J = 8.4 Hz, 1 H; SerNH), 5.46 (dd, 1H;H4), 5.31 (dd, ,J(3,4) = 3.0Hz, 1 H; H3). 5.01 (d,
'J(l.2) = 3.6 Hz, 1 H ; Hl), 4.96 (m. 1 H ; Ser-CHoc). 4.48 (m, 2 H ; FmocCH,), 4.34 (dd, *J= 11.2 Hz, ' J = 3.4 Hz, 1 H ; Ser-CHD-a), 4.26 (t. 1 H ;
Fmoc-CH), 4.18 (t. 1 H ; H5), 4.10 (dd, 'f = 3.8 Hz, 1H ; Ser-CHD-b),4.08
(dd, 2J(6d,b)=11.0Hz, 'J(5,6d)=6,0HZ, 1 H ; H6d). 4.03 (dd,
,J(5,6b) = 7.6 Hz, 1 H, H6b), 3.72 (dd, 'J(2,3) = 11.O Hz, 1 H ; HZ),2.16,
2.07, 1.98 (3s, 9 H , 3 xCOCH,). FAB-MS: m/; 807.3 ( M + l ) (calcd for
C,,H,,F,N,O,,:
M , = 806.2).
[13] E. Atherton, C.J. Logan, R. C. Sheppard, J Chem. SOC.Perkin Truns. 1
1981, 538-546.
[14]a) F. Albericio, N . Kneib-Cordonier, S. Biancaiana, L. Gera, R. J
Masada, D. Hudson, G. Barany, J Org. Chem. 1990,55,3730- 3743; b) H.
Diirr, A. G. Beck-Sickinger. G. Schnorrenberg, W. Rapp, G. Jung, I n [ . J.
Pepl. Protein Res. 1991, 38, 146-153.
[15] P. SchultheiB-Reimann, H. Kunz, Angrw. Chrm. 1983. 95. 64; Angew
Chem. Int. Ed. Engt. 1983, 22, 62.
[16] E. Atherton, J. L. Holder, M. Meldal, R. C. Sheppard, R. M. Valerio, J.
Chem. Soc. Perkin Trans. 1 1988, 2887-2894.
[I71 L. R. Cameraon, J. L. Holder, M. Meldal. R. C . Sheppard. J. Chem. Sol.
Perkin Trans. 1 1988, 2895-2901.
[IS] a) H. Kunz, H. Waldmann, Helv. Chim. A r m 1985, 68, 618-622; b) H.
Kunz, S. Birnbach, Angew. Chrm. 1986, 98, 354-355; Angeiv. Chem. lnr.
Ed. Engl. 1986, 25, 360.
[19] S. Peters, T. Bielfeldt, M. Meldal, K. Bock, H. Paulsen, f. Chcm. Snc.
Perkin Trans. 1. 1992, 1163-1171.
[20] a) A. Holm, M. Meldal, Peptides 1988 (Eds.: G. Jung, E. Bayer). Proc.
20th Eur. Pept. Symp. de Gruyter, Berlin, 1989, p. 208-210; b) A. Dryland, R. C. Sheppard, Tetrahedron 1988,44, 859 -876.
[21] The yields are calculated on the degree of loading of the resin and the
degree of coupling of the first amino acid. Both were determined by quantitative amino acid analysis with Nle as internal standard.
[22] 14:[a]E2= +113.7(c =l.0inwater);FAB-MS:m/z1893.9(M+l)(calcd
for C,,H,,,N,,O,,:
M , = 1892.9).
[23] J. R. Gum, J. C. Byrd, J. W. Micks, N. W. Toribara, D.T.A. Lamport. Y. S.
Kim, J1 Bid. Chem. 1989, 264,6480-6487.
CAS Registry numbers:
1,67817-37-2;2,86061-06-5;
3,86061-05-4; 4,141462-10-4; 5,141462-11-5;12,
137816-32-1; 13, 137816-56-9; 14,141462-18-2; CH,COSH, 507-09-5.
[I] a) H. Kunz, Angew. Chem. 1987,99,297-311; Angew. Chem. Int. Ed. Engl.
Deuterium-Induced Phase Transition of an
1987. 26, 294-308; b) H. Paulsen, ibid. 1990, 102, 851 -867 or 1990, 29,
Organic Metal--An Unusual Isotope Effect**
823-839.
121 J. Montreuil, Adv. Carbohydr. Chem. Biochem. 1980, 37, 157-223.
By Siegfried Hiinig,* Klaus Sinzger, Martina Jopp,
[3] a) J. L.Winkelhake, GlycoconjugateJ. 1991,8,381-386; b) T. A. Springer,
Nuture 1990, 346, 425-434.
Dagmar Bauer, Werner Bietsch, Jost Ulrich von Schiitz,
[4] I. Brockhausen, G.Moller, G. Merz, K. Adermann, H. Paulsen, Biochemand Hans Christoph Wolf
islry 1990, 29, 10206-10212.
151 a ) H . Paulsen. G. Merz, U. Weichert, Angew. Chem. 1988, 100, 1425In this report the extreme sensitivity['] of the metallic con1427; Angew. Chem. Znt. Ed. €Jig/.1988,27,1365-1367; b) H. Paulsen, G.
ductivity of 2-(Me,-DCNQI),Cu (DCNQI=N,N'-dicyanoMerz. S. Peters, U. Weichert. Liehigs Ann. Chem. 1990,1165-1173; c) B.
quinonediimine) to minor structural changes is demonstratLunning. T. Norberg, C . Rivera-Baeza, T. Tejbrant, Clvcoconjugute J.
ed in a striking manner. Whereas the conductivity of the
1991, 8, 450-455; d) E. Bardaji, J. L. Torres, P. Clapes, F. Albericio, G.
Barany. R. E. Rodriguez, M . P. Sacristan, G. Valencia, J. Chem. Soc.
copper salt of non-deuterated 2,5-Me2-DCNQI increases as
Perkin Truns. 1 1991,1755-1759; e) E Filira, L. Biondi, F. Cavaggion, B.
the temperature is lowered (to 0.45K) and reaches
Scolaro. R. Rocchi, Int. J. P e p . Protein Res. 1990, 36, 86-96; f) F. Filira,
500000 Scm-' at 10K, the partially or fully deuterated
L. Biondi. B. Scolaro, M. T. Foffani, S. Mammi. E. Peggion, R. Rocchi,
derivative switches from quasi three-dimensional behavior
Int. J B i d . Macromol. 1990, 12, 41 -49.
[6] H. Paulsen. K. Adermann, Liebigs Ann. Chem. 1989, 751 -769.
with CT z lo3 Scm-' at room temperature to quasi one-di[7] a) M. Meldal, K. J. Jensen, J. Chem. Sue. Chem. Commun. 1990,483-485;
mensional conduction below the transition temperature
b) A. M. Jansson, M. Meldal, K. Bock, TetrahedronLett. 1990,31, 6991TM-,.As a result, CT changes by about eight orders of magni6994: c) M. Meldal. K . Bock, ibid. 1990,31, 6987-6990; d) K. J. Jensen,
tude within a few K.
M. Meldal, K. Bock. Peptides 1991, Proc. 12th Am. Pept. Symp., in press.
[8] S. Peters, T. Bielfeldt. M. Meldal. K. Bock, H. Paulsen, Tetrahedron Lett.
1991. 32, 5067-5070.
['I Prof. Dr. S. Hunig, Dipl.-Chem. K. Sinzger, M. Jopp
[9] H. Paulsen, Angen. Chem. 1982.94.184-201 ; Angew. Chem. l n t . Ed. Engl.
Institut fur Organische Chemie der Universitat
1982, 21, 155-173.
Am Hubland, D-W-8700 Wiirzburg (FRG)
[lo] H. Paulsen. A. Richter. V. Sinnwell, W. Stenzel, Curbohydr. Res. 1978, 64.
D. Bauer, DiplLPhys. W. Bietsch. Dr. J. U. von Schutz,
339 -364.
Prof. Dr. H. C. Wolf
[ l l ] I. Schon, C.Kisfaludy, S.ynthesis 1986, 303-305.
3. Physikalisches Institut der Universitit
[12] 4:[a]:' = 39.8 ( c = 1.0 in chloroform); m.p. 78 "C; 'H NMR (400 MHz,
Pfaffenwaldring 57, D-W-7000 Stuttgart (FRG)
C,D,. 2 7 ° C TMS): 6=7.58-7.14 (4m, 8 H ; areneH), 5.96 (d,
3J=8.5H~,1H;Thr-NH),5.59(dd,1H;H4),S.48(dd,3J(3,4)=3.0Hz,[*"I This research was supported by the Fonds der Chemischen Industrie, the
1H;H3),5.02(d.3J(l,2)=3.5Hz,1H;H1),4.72(m,1H;Thr-CHi),4.48
Volkswagen Stiftung, and the Deutsche Forschungsgemeinschaft (SFB
(dd, ' J = 10.5 Hz. ' J = 4.0 Hz, 1 H ; Fmoc-CH,-a), 4.37 (dd, ,J =
3291.
+
A n g e w . Chem. I n r . Ed. Engl. 1992. 31, No. 7
g
VCH VerlugsgrsellschufimbH, W-6940 Weinheim, 1992
0570-08~~3/92~0707-0859
$3.50 + .25/0
859
Systematic studies have shown that all of the copper-radical-anion salts 1 derived from 2,5-disubstituted DCNQIs
with the combination of substituents R’ = R 3 and
R 1 iR3 = CH,, OCH,, CI, Br, I crystallize in the same
space group, 14,/a, and demonstrate metallic conductivity at
least at room temperature.[21 Starting with about 2001000 S cm- (at room temperature) the conductivity increases steadily with cooling. If the substitution pattern of 1 is
determined primarily by the small substituents CI and Br,
then a phase transition to a metal-like semiconductor (for
definition see ref.r31)takes place at TM-,= 160-230K; the
large substituents OCH, and I guarantee metallic conductivity down to the lowest temperatures.
K-
Yl:D)I
N,
CN
1
cu
?
.
L
H
-
CD,
H
50
CD,
H
73
CD3
D
02
Br
H
160
Br
H
160
la
CH,
CH,
lb
CH,
lc
CD,
Id
CD,
le
CH,
lf
Br
For this class of materials it is already known that continuous cooling leads to increased compression of the c axis of
the crystal lattice (for l a a total of 2%), while the a axis is
lengthened minimally (for 1 a about 0.09 %).I4.
’I The associated flattening of the nearly tetrahedral coordination of the
ligands to copper (enlargement of the coordination angle a ;
cf. Fig. 1) splits the t,, set of copper 3d orbitals, which are
degenerate for ideal tetrahedral coordination, as a result of
When the
the reduction in symmetry from Tdtowards DZd.[61
coordination angle a exceeds a critical threshold (127128 o),[61 the crystal undergoes a phase transition recognizable
by an additional discontinuous compression of the c axis.14*
Recently a sevenfold’ super-diamond structure was revealed for the DCNQIkopper salts.17a1Closer examination
of a super-adamantane unit in the direction of stacking
(Fig. 2) shows that the DCNQI stacks associated with four
neighboring stacks of copper atoms form a super helix of
seven intertwined single helices,17b1whose spacing in the direction of stacking has the value of the cell constant c.
N
Fig. 1. Coordination geometry of the Cu central atom of the salts (2,5-R’,R3DCNQI),Cu. N represents the cyano N atoms of the ligands.
The channel formed by the helices is filled by the DCNQI
substituents R‘ and R3; their size thus determines the distance between the individual helices. For the previously described structural type, a direct relationship between the cell
constants a and c and the crucial coordination angle c i can be
deduced.[’’ Combinations of smaller substituents (R‘ = Cl,
Br; R 3 = CI, Me, Br) allow a phase transition; combinations
of large substituents (R’ = I, MeO; R 3= CI, Me, Br, I,
MeO) prevent one. Thus there is a three-dimensional cooperative interaction of the partners, whose effect on the conductivity is produced by a collective of an “infinite” number of
‘‘layers’’ (DCNQIs).C9]
A thorough analysis of these relationships[’,
showed
that l a occupies a special position. Although the van der
Waals volume of the CH, group (21.7
is substantially
less than that of Br (25.1 w3),[’11 l a (CHJCH,) does not
undergo a phase transition until the lowest temperatures, in
constrast to l e (CH,/Br) and 1f (Br/Br). On the contrary, its
conductivity increases markedly until 0.45 K[”] and reaches
500000 Scm-‘ at 10K[131(cf. Fig. 3). This unexpected stability of l a is attributed to the low LUMO energy
(
E = -~ 2.42 ~eV) and
~
the~ enhanced donor strength of the
n electron pair of the CN group (con = - 14.51 eV) relative to
1e (
E = -~ 2.64 ~eV, E,,~ = ~ 14.64 eV) and 1 f (
E =
- 2.85 eV, E,, = - 14.77 eV.[’O]
If all of these explanations are correct, then substituents
with electronic properties similar to those of methyl groups
but with a smaller volume may possibly trigger a phase transition upon cooling. Both the electronic and the spacial prerequisites are met by CD, groups, whose volume at 70 K is
about 1 .O- 1.5 % less than that of CH, groups.
w3)
Fig. 2. Sevenfold adamantane super-structures in the
crystal lattice of (2,5-R’,R3-DCNQI),Cu (space group
141,J.
Cu ions take the place of adamantane C atoms and
are connected to each other through the ligands. In both
figures three-fourths of the ligands between the copper
ions are represented by lines. (SCHAKAL 88B/V16).
Left: Side view perpendicular to the direction of stacking.
The substituents R’ and R3 are not shown. Right: Perspective view in the direction of stacking. The substituents R‘ and R’ fill the channels.
860
6
VCH Verlagsgesellschaft mbH, W-6940 Weinheim, 1992
0S70-0833/92/0707-0860$3.50+ .25JO
Angew. Chem. In[. Ed. Engl. 1992, 31, No. 7
~
~
As a result of the lower zero-point energy, the mean as well
as the maximum C-D bond length is less than the comparable values for a C-H bond in the gas phase, 0.15 % and
0.37 %, r e ~ p e c t i v e l y .Correspondingly,
~’~~
the molar volume
of liquid CD, relative to CH, at 100K is about 1 YOless;[’51
the volume of the unit cell in the crystalline state at 70K is
approximately 1.5 % less.[’61As the following literature examples show deuteration of the methyl groups in 1 a should
result in only minimal quantitative changes. H / D exchange in
crystalline organic charge-transfer (CT) complexes shifts the
transition temperature of the structural phase transition
from +0.75 K[17]to - 15 K.[I8I For deuterated superconductors of the BEDT-TTF type an increase in the critical
temperatures by 0.28 K to 0.6 K[I9]is observed; however, for
deuterated (TMTSF),CIO, a decrease of 0.13 K[’O1 is noted.
In contrast, we report here a dramatic qualitative effect,
that is, a phase transition from metallic to semiconducting
behavior induced by deuteration. Such a phenomenon due to
a secondary deuterium isotope effect has not been reported
so far.
As is evident from Figure 3, the introduction of deuterium
to just one CH, group in 1 a (CH,/CH,/H,) giving 1b (CH,/
CD,/H,) induces a phase transition at 58 K. The two CD,
106
other DCNQI-Cu salts is quite different. Whereas the line
width of the ESR signal observed for non-deuterated systems increases upon warming from low temperature to TM-,
(increase of the three-dimensional movement of the electrons), the line width for the deuterated copper salts is practically constant below TM-,;
this supports the assumption of
a transition from three-dimensional to an extremely one-dimensional
Despite its high static susceptibility,[*] this signal is not detectable in the metallic region. Because of the three-dimensional movement of the electrons,
the spin-orbit coupling leads to extreme line widths.[2s1
Apparently 1a is protected only minimally from a phase
conversion by the electronic properties mentioned. Thus
slight changes cause the phase transition in the dimensionality of the movement of the electrons. Besides the deuteration
described here, the same effect is induced by applying pressure to 1a,[”, 261 Even 3 10 bar produces a sharp phase transition at 47K (or 400 bar at 76K). The conductivity drops
sharply by at least a factor of lo4, analogous to the observations for the deuterated systems (Fig. 4).[”]
0.0
4
cu
0.4
2
1:
10-2 2
-
lo-’ >
-
10-5
10-6
v
-
-
I
0
60
T
v
v
0.8
1.2
v
4
v
v
4
%
4v
400bar
4
v
1.6
4
I
I
I
60
T [KI
-
I
I
80
1
Fig. 4. Pressure dependence of the conductivity of la[12].
I
I
I
120
180
240
300
T [KlFig. 3. Temperature dependence of the conductivity u of 1a (CHJCHJH,), 1b
(CHJCDJH,), l c (CDJCDJH,), and I d (CD,/CD,/D,) (four-point measurements on single crystals[23].)
groups in 1c (CD,/CD,/H,) trigger this conversion already
at 73 K. Even the substitution of the two hydrogen atoms on
the ring in 1c by deuterium to 1d (CD,/CD,/D,) shifts the
phase-transition temperature by another 9 K to 82 K.[”] The
resulting phase transitions are unusually sharp: The conductivity drops off by a factor of 106-108 (!) within 1-2K.[”l
The phase transition of the deuterated Cu salts can also be
proved by electron spin resonance spectroscopy: Below the
phase-transition temperature a relatively narrow ESR signal
(ABppz2.
T) is observed, whose intensity increases
drastically with decreasing temperature. The behaviour of
Angew. Chem. Ini. Ed. Engl. ‘-92, 31, N o . 7
(0VCH
Besides the somewhat smaller volume of the CD, group,
its different rotational barrier could be significant. Studies of
crystals of several deuterated compounds (CD,C0,Li,1271
and CD,C,D,L28. ” I ) by inelastic neutron
CD,NO, ,[’‘I
scattering show a marked decrease in the tunnel splitting and
thus an increase in the rotation barriers relative to those of
the corresponding protonated systems. As a consequence,
the motion of the deuterated methyl groups is frozen even at
higher temperatures. One argument against this interpretation of our results is that for the reported activation energies
at 500-800K[301 due to intra- and intermolecular hindran~e,[~’I
the motion of the methyl groups of the nondeuterated copper salt l a would be too slow at the finite
[*] Note added in proof: At exactly T, ,the static susceptibility exhibits a step
in intensity by 1.5 x
emug-’ to increase considerably with lower temperatures. At 7 K a pronounced peak occurs due to magnetic ordering.
Verlugsgesellschujt mbH, W-6940 Weinheim, 1992
0570-0833~92/0707-0S61S 3.50+.2S/0
861
temperature to prevent a phase transition. Further experiments should clarify the situation.
Received: February 13, 1992 [Z5188IE]
German version: Angew. Chem. 1992, 104, 896
CAS Registry numbers:
l a , 103420-86-6; 1 b, 141636-02-4; l c , 141636-05-7; Id, 141636-07-9; le,
112019-20-2; If, 111958-83-9.
[I] J. U. von Schiitz, H. Rieder, H. C. Wolf, H. Meixner. S. Hiinig, Synth.
Me!. 1991. 42, 1761.
[2] Reviews: a) S. Hunig, P. Erk, Adv. Marer. 1991,3, 225-236; b) S. Hiinig,
Pure Appl. Chem. 1990,62, 395-406.
[3] J. S. Miller, A. J. Epstein, Angex.. Chem. 1987,99,332-339; Angew. Chem.
Int. Ed. Engl. 1987, 26, 287-293.
[4] R. Moret, Synrh. Met. 1988, 27, B301bB307.
[5] a) H. Kobayashi, R. Kato, A. Kobayashi, T. Mori, H. Inokuchi, SolidState
Commun. 1988,65,1351-1354; b) A. Kobayashi, T. Mori. H. Inokuchi, R.
Kato, H. Kobayashi, Svnrh. Met. 1988,27, B275-B280; c)S. Kagoshima,
N. Sugimoto, R. Kato. H. Kobayashi, A. Kobayashi, ibid. 1991, 41-43,
1835-1838.
[6] a) A. Kobayashi. R. Kato, H. Kobayashi, T. Mori, H. Inokuchi, SolidState
Commun. 1987, 64, 45-51; b) H. Kobayashi, R. Kato, A. Kobayashi, T.
Mori, H. Inokuchi, Y Nishio, K. Kajita, W. Sasaki, Synrh. M e f . 1988,27,
A289-A297; c) R. Kato, H. Kobayashi, A. Kobayashi, 1 Am. Chem. Soc.
1989, 111, 5224-5232.
(71 a) 0 . Ermer, Adv. Marer. 1991,3,608-611. b) Similar helix structures have
been described for other super-diamond lattices: 0.Ermer, L. Lindenberg,
Chem. Ber. 1990, 123, 1111.
[8] An exact evaluation of these new structural considerations and their implications for the discussion of phase behavior will be published shortly.
[9] For properties induced by collectives of molecules see: F. M. Menger,
Angew,. Chem. 1991,103,1104; Angew,. Chem. Inr. Ed. Engi. 1991,30,1086.
[lo] P. Erk, H. Meixner, T. Metzenthin, S. Hiinig, U. Langohr, J. U. von
Schiitz, H.-P. Werner, H. C. Wolf, R. Burkert, H. W. Helberg, G. Schaumburg, Adv. Mater. 1991. 3, 311-315.
[ l l ] A. Bondi, J. Phvs. Chem. 1964,68,441-451. The special position of l a is
even more apparent by application of these newer van der Waals volumes
(K. Sinzger, Dissrrfation, UniversitLt Wiirzburg, 1992).
[12] S. Tomic, D. Jerome, A. Aumiiller, P. Erk, S . Hiinig, J. U. von Schiitz, J.
Phys. C : Solid State Phys. 1988. 21, L203-L207.
[13] A. Aumiiller, P. Erk, G. Klebe, S. Hiinig, J. U. von Schiitz, H.-P. Werner,
Angew. Chem. 1986, 98, 759-761; Angew. Chem. Int. Ed. Engf. 1986,2S,
740.
[14] L. S. Bartell, K. Kuchitsu, R. J. deNeui, J Chem. Phys. 1961, 35, 12111218.
[lS] S. Fuks, J.-C. Legros, A. Bellemans, Physica 1965, 31, 606-612.
[16] S. C. Greer, L. Meyer, J Chem. Phys. 1970, 52. 468-469.
(171 J. R. Cooper, J. Lukatela, M. Miljak, J. M. Fabre, L. Giral, E. Aharon
Shalom, Solid State Commun. 1978, 25, 949-954.
[18] N. S. Dalal, L. V. Haley, D. J. Northcott, J. M. Park, A. H. Reddoch. J. A.
Ripmeester, D. F. Williams, J. Chem. Phys. 1980, 73, 2515-2517.
[19] a) C:P. Heidmann, K. Andres, D. Schweitzer, Physica 1986, 14338, 357359; b) K. Oshima, H. Uruyama, H. Yamochi, G. Saito, J Phvs. Soc. Jpn.
1988,57, 730-733.
[20] H. Schwenk, E. Hess, K. Andres, F. Wudl, E. Aharon-Shalom, Phys. Lett.
A 1984, 102, 57-60.
1211 The syntheses will be reported elsewhere. All new compounds provided the
expected spectroscopic and analytical data. The extent of deuteration was
determined by 'H NMR spectroscopy (250 MHz) and confirmed by mass
spectrometry. I b (D3: 99.5%); l c (D6: > 99.5%); I d (D6: 99.5%;
D,: 97.3%).
(221 A careful analysis of the IR data of 1d (C. Pecile, personal communication)
conducted parallel to the measurements described here also demonstrated
the phase transition. We thank Prof. Pecile for the results and for providing
us with 100 mg of I d for comparison.
[23] All four-point measurements with Tl and Tt were repeated a number of
times on various samples.
1241 J. U. yon Schiitz, unpublished.
[25] J. U.von Schutz, H.-P. Werner, H. C . Wolf, A. Aumiiller, P. Erk, S . Hiinig,
Proc. 23th Congr. Ampere M a p . Rson. 1986, 158-159.
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Doubly Bridged Prismane and Dewar Benzene
Intermediates in an Unusual Photochemical
Rearrangement of Tricyclic Phthalic Esters**
By R o y Gleiter* and Bjorn Treptow
Dedicated to Professor Giinther Maier
on the occasion of his 60th birthday
Irradiation of alkylbenzenes in solution at wavelengths
higher than 250 nm usually yields a positional isomerization
of the alkyl groups."] To rationalize this phenomenon, it is
assumed that valence bond isomers of benzene, such as benzvalene, Dewar benzene, and prismane are short-lived intermediates. The involvement of such isomers has been inferred
from isotopic labeling experiments."' Possible ring transposition processes that give rise to apparent 1,2 and 1,3 shifts
are shown schematically in Scheme 1 .
4
x
Scheme 1. Proposed rearrangements that proceed via valence isomers of benzene as intermediates.
Two motives prompted us to study the mechanism of the
light-induced ring transposition in benzene: 1) We thought
that the tethering of neighboring centers in a benzene derivative might stabilize one ofthe intermediates, and 2) we hoped
by this "rope trick" to generate those doubly bridged Dewar
benzenes and/or prismanes which were not available to
date.[*]
We started our investigations with the doubly bridged Dewar benzene derivatives 1, which could be obtained easily from
cyclic alkynes and dimethyl acetylenedicarboxylates.t2,31 Ir['I
Prof. Dr. R. Gleiter, Dipl.-Chem. B. Treptow
Organisch-chemisches Institut der Universitat
Im Neuenheimer Feld 270, D-W-6900 Heidelberg (FRG)
[**I We are grateful to the Volkswagen-Stiftung, the Deutsche Forschungsgemeinschaft, the Fonds der Chemischen Industrie, and the BASF AG (Ludwigshafen) for financial support.
057o-Oa33192107o7-0862B 3.50f ,2510
Angew. Chem. I n f . Ed. Engl. 1992. 31, No. 7
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