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First Structure Analysis and Photoelectron Spectroscopic Investigation of an Azete and an Azete-Cobalt Complex.

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(Fig. 1). For vinylcyclopropanes, 1 has an energetically
high-lying “Walsh orbital” in the three-membered ring,
which, together with the 71-system of the double bond has
suitable symmetry for interaction with the LUMO of Z.1141
The endo-addition is preferred over the exo-addition, presumably on steric grounds (hindrance by the methoxycarbony1 group in 1).
H
H
Fig. I . Interaction of the LUMO of tropone with the second highest occupied
M O of homopyrrole.
According to Houk and Woodward,”sl 2,5-dimethyl-3,4diphenylcyclopentadione and tropone form a [4 61-cycloadduct. The product is present in the exo-configuration ;
at elevated temperatures it rearranges by intramolecular
Diels-Alder reaction into a cage compound. The structure
of the hypothetical [4 6]-adduct 3 was calculated using
the semiempirical method AM1.[l6]The molecular geometry obtained after optimization of all parameters (Fig. 2)
shows that the diene unit and the double bond of 3 are
fixed by the molecular skeleton in a n arrangement that is
favorable for the subsequent D i d - A l d e r reaction leading
to 7.
+
Received: June 27, 1988 [ Z 2831 IE]
German version: Angew. Cltem. 100 (1988) 1618
CAS Registry numbers:
1, 31709-40-7; 2, 539-80-0; 7, 117409-34-4
[I] J. Bauer, I. Ugi, J. Chem. Res. Synop. 1982, 298; J . Chem. Res. Miniprint
1982, 3101, 3201 ; see also J . Bauer, Dissertation. Technische Universitat
Miinchen 1981.
121 J. Dugundji, 1. Ugi, Top. Curr. Chem. 39 (1973) 19; see also V. Kvasnii-ka, M. Kratochvil, J. Koi-a, Collect. Czech. Chem. Commun. 48 (1983)
2284; V. KvasniEka, ibid. 48 (1983) 2097, 2118; I. Ugi, J . Indiun Chem.
Soc. 62 (1985) 864; J . Brandt, 1. Ugi (Eds.): Proc. 8th ICCCRE llnt.
Con5 Comput. Chem. Res. Educ.), Hiithig, Stuttgart, in press.
[3] 1. Ugi, E. Fontain, J. Bauer, Anal. Chim. Actu 210 (1988) 123.
[4] J. Bauer, E. Fontain, I. Ugi, Tetrahedron Comput. Methodol. I (1988)
No. 2, in press.
[5] J. Brandt, J. Bauer, E. M. Frank, A. von Scholley, Chem. Scr. 18 (1981)
53; J . Brandt, A. von Scholley, Comput. Chem. 7 (1983) 51; J. Brandt, A.
von Scholley-Pfab, H. Schonmann, M. Wochner, Vortrug ACHEMA
1988.
[6] J. Bauer, R. Herges, E. Fontain, I. Ugi, Chimia 39 (1985) 43.
[7] R. Herges, Tetrahedron Comput. Methodol. I(1988) 15.
[8] F. W. Fowler, Angew. Chem. 83 (1971) 148; Angew. Chem. Int. Ed. Engl.
10 (1971) 135.
[9] For analogous reactions with homofuran and homothiophene see R.
Herges, I. Ugi, Angew. Chem. 97 (1985) 596; Angew. Chem. Int. Ed.
Engl. 24 (1985) 594; Chem. Ber. 119 (1986) 829.
[lo] A. Gieren, T. Hiibner, unpublished.
[I I ] W. Schubert, I. Ugi, J. Am. Chem. SOC.100 (1978) 37; Chimiu 33 (1979)
183; I. Ugi, J. Dugundji, R. Kopp, D. Marquarding: Perspectives in Theoretical Stereochemistry (Lecture Note Ser. 36). Springer, Berlin 1984,
Chapter 8.
[I21 E. Fontain, J. Bauer, 1. Ugi, G e m . Lett. 1987. 37; 2. Nuturforsch. 8 4 2
(1987) 889.
[I31 R. Hoffmann, R. B. Woodward, J . Am. Chem. SOC.87 (1965) 4388.
[I41 The molecular orbitals were calculated with M N D O as described by M.
J. S. Dewar, W. Thiel, J. Am. Chem. Soc 99 (1977) 4899.
[IS] K. N. Houk, R. B. Woodward, J. Am. Chem. Soc. 92 (1970) 4145.
[I61 M. J. S. Dewar, E. G. Zoebisch, E. F. Healy, J. J . P. Stewart, J . Am.
Chem. SOC.107 (1985) 3902.
+
First Structure Analysis and Photoelectron
Spectroscopic Investigation of an Azete and an
Azete-Cobalt Complex**
By Martin Ledermann, Manfred Regitz,*
Klaus Angermund, Paul Binger, Carl Kriiger.
Richard Mynott, Rorf Gleiter, and Isabella Hyla-Kryspin
Dedicated to Professor Robert Carrie on the occasion of
his 60th birthday
In contrast to cyclobutadienes,”’ no crystal structure investigations of azetes (azacyclobutadienes) have hitherto
been described in the literature. The synthesis of 3,[*l
the first kinetically stabilized azete, provided us with the
chance of studying the influence of the ring nitrogen atom
o n the structure of the molecule. However, because of a
phase transformation at - 75 “C, the crystal structure anal[*] Prof. Dr. M. Regitz, DipLChem. M. Ledermann
\ ’
Fig. 2 The structure of the [4+6Il-adduct 3 calculated by AM1
Experimental
7 : N-methoxycarbonyl-l-aza[3.l.O]bicyclohex-3-ene
1 (0.66 g, 4.7 mmol) was
treated with 0.5 g (4.7 mmol) of 2 at 180°C in the absence of solvent. The
reaction product was recrystallized from toluene. Yield: 92O10; m.p. 173174°C.
Angew. Chem. l n t . Ed. Engl. 27 (1988) No. 11
Fachbereich Chemie der Universitat
Erwin-Schrodinger-Strasse, D-6750 Kaiserslautern (FRG)
Dr. K. Angermund, Prof. Dr. P. Binger,
Prof. Dr. C . Kriiger, Dr. R. Mynott
Max-Planck-Institut fur Kohlenforschung
Kaiser-Wilhelm-Platz 1, D-4330 Miilheim a. d. Ruhr (FRG)
Prof. Dr. R. Gleiter, Dr. I. Hyla-Krypsin
Organisch-chernisches lnstitut der Universitat
Im Neuenheimer Feld 270, D-6900 Heidelberg (FRG)
[**I Antiaromatics, Part 25. This work was supported by the Deutsche Forschungsgemeinschaft, the Fonds der Chemischen Industrie, and the Stiftung Vo1kswagenwerk.-Part 24: U. Hees, U.-J. Vogelbacher, G . Michels, M. Regitz, Tetruhedron 44 (1988), in press.
0 VCH Verlugsgesellschujt mbH. 0-6940 Weinheim, 1988
0S70-0833/88/1111-1SS9 $ 02.50/0
1559
ysis of 3 (m.p. 37°C) could only be carried out above this
temperature and the results were unsatisfactory due to disorder effects in the region of the methyl groups. In order to
acquire accurate information about the azete structures we
have now prepared and investigated the unequally substituted antiaromatic heterocycle 2 and the cobalt complex
C1Q
c,8
5.
The novel azete 2 is formed in analogy to the synthesis
of 3 by thermolysis of the cyclopropenyl azide 1[31 in a
pressure Schlenk tube in the form of extremely oxygensensitive, reddish-brown crystals (SO%, m.p. 59"C, from
pentane at - 78 "C). The ring expansion is highly selective;
there is no NMR evidence for the formation of the isomeric 2,4-di-tert-butyl-3-mesitylazete.
Me
Me
Me
125 OC,
CHC13
2bar
Me
%3
,-
1
28
2A
y
+
3
C17
0
I
\'
co
"-C5H12#
'4
$t5
I
loot,
- 2 CHZ=CHz
4
The complex 5 is obtained as light-brown crystals (79%,
m.p. 117"C, from pentane at -78°C)'51 on reaction of 3l2]
with cyclopentadienylbis(ethy1ene)cobalt 4 ;I4]5 is the first
metal complex of an azete.f61
The crystal structure analysis of the azete 2 (Fig. 1, top)
clearly shows that the antiaromatic compound crystallizes
as the valence isomer 2A. The four-membered ring has a
planar, distorted rectangular structure with long C2-C3
and N-Cl single bonds (1.59(1) and 1.58(1) A, r e ~ p . ) ; [the
~]
lengths of the Cl-C2 and N-C3 double bonds, on the
other hand, are normal. Steric interaction of the mesityl
moiety with the neighboring tBu group leads to an interplanar angle of 70" between the two rings, so that a ninteraction with the four-membered ring is almost impossible (see also the photoelectron (PE) spectrum). The bulky
ring substituents are responsible for the, in part relatively
large, widening of the exocyclic angles C2-Cl-C4,
C3-C2-C13, and C2-C3-C17.
On comparing these findings with the structural data of
kinetically stabilized cyclobutadienes,['] one finds several
parallels to the methyl tri-tert-butylcyclobutadienecarboxylates with regard to four-membered ring geometry, the angle of the plane of the substituent relative to the ring, and
the steric effects on the exocyclic bond angles.191This close
relationship also manifests itself on comparing the first
band in the He(1)-PE spectrum of this cyclobutadiene with
that of 3.['01
The I3C-NMR spectrum of 2 measured at 40°C (75.5
MHz, [D&oluene) shows three sharp singlet signals for the
four-membered ring ( 6 ~ 2 0 0 . 9 , 141.2, 151.2).'''1 These
largely temperature-independent resonances"'] can be assigned to the carbon atoms C2, C3, and C4 of the valence
isomer ZA, which is also present in the crystalline state. A
valence isomer equilibrium 2A?+2B is thus, other than in
1560
0 VCH Verlagsgesellschafl rnbH. 0-6940Weinherrn, I988
P
c10
/- \
U C l l
Fig. I . l o p : Molecular structure of 2. C20H29N:P2,/c, u = 14.256(3),
b=8.222(1), C = 16.078(4)
8=93.06(2)', T=2OoC, 2 = 4 , pca,,d= 1.00 g
cm-3, jl(MoKa)=0.53 c m - ' . Enraf-Nonius diffractometer CAD-4; 4686
measured reflections, averaged to 424, 1043 observed (1>2u(I)): R=0.076,
R,. =0.071 ( w = I/u2(F0)) for 190 parameters [8].Selected bond lengths
and angles["]: N-CI l.58(1), N-C3 l.28(1), CI-C2 l.35(1), C2-C3 1.59(1),ClC 4 1.48(1), C2-CI3 l.49(1), C3-CI7 l.48(1); Cl-N-C3 87.4(6), N-CI-C2
92.6(6), Cl-C2-C3 84.9(6), C2-C3-N 95.1(6), N-CI-C4 124.3(7), C2-CI-C4
143.1(8), CI-C2-C13 134.5(7), C3-C2-C13 140.6(7), C2-C3-C17 137.7(7), NC3-CI7 127.3(8).-Bottom: Molecular Structure of 5 . C20H32CoN;Pbcu.
~=14.179(5),b = 16.82(1), ~=15.939(6)A, T = -162"C, Z = 8 , p - ~ =1.21 g
cm-', p(MoK,)=8.98 c m - '. Enraf-Nonius diffrdctometer CAD-4; 25564
measured reflections, averaged to 1 1 622 (R,,,=0.06), 4516 observed
( 1 > 2 u ( I ) ) : R=0.046, R,, =0.040 ( w = l/n2(F0)) for 327 parameters [S]. Selected bond lengths [A] and angles I"]: N-Co 1.958(2), C2-Co 2.027(2), C3-cO
1.958(2), Cl-Co 1.960(2), N-C3 1.433(2), N-CI 1.424(3), C2-C3 1.462(3), C2CI 1.478(3), N-C3-C2 92.8(2), N-CI-C2 92.5(2), C3-C2-C1 85.8(2), C3-N-Cl
88.9( I).
A,
[A]
the case of 3,Iz1not detectable; the isomer 2B participates
at best to the extent of 5%. The signals were assigned with
the help of a 2D-'3C,'H-correlated spectrum (optimized
for long-range couplings nJtC,HJ,
on the basis of estimations of the chemical shifts and by a comparison of the
signal position of the azomethine carbon atom C-2 with
the signals in the low-temperature spectrum of 3.
0570-0833/88/1111-1560 S 02.50/0
Angew Chem. In1 Ed. Engl. 27 (1988) No. 11
Table I. Orbital sequence of 5, Me instead of tBu, calculated according to
the I N D O method.
8
9
10
11
r
eV1
12
13
14
15
16
M
&
7
,
L
I
8
9
10
11
IIeVl
12
36
35
34
33
32
31
30
29
- 8.74
- 9.02
- 10.70
-11.25
-11.40
-11.62
- 11.96
- 12.10
8
3
40
47
34
22
88
80
% L
%Cp
37
51
45
35
26
61
8
13
55
46
15
18
40
17
4
7
MO type
@), which we assign to the ionization from the two MOs
2b,(71) and 5a,(o) (see below). The ionization energy for
lbl(x) is, according to the PE spectrum, 10.7 eV (band 0).
Comparison of the PE ionization energies with the results
of MO calculations (semiempirical and ab initio metho d ~ confirms
~ ~ ~ this.
~ )
The crystal structure analysis of the cobalt complex 5
(Fig. 1, bottom) reveals that the bond lengths in the planar
four-membered ring become much more similar as a result
of electron delocalization (1.478(3)) and 1.462(3) A for CC and 1.424(3) and 1.433(2) A for N-C). The distances of
N, CI, and C3 to the metal atom are almost equal, only the
C2-Co distance is somewhat longer. The coplanarity of the
two rings (interplanar angle: 2") indicates an analogous
situation in the case of the Co-C cyclopentadiene distances. The bonds of the quaternary tBu-C atoms C4, C8
and C12 to the azete C atoms are bent out of the plane of
the four-membered ring away from the Co atom by 9", 10"
and 11 re~pectively."~~
According to INDO c a l ~ u l a t i o n the
s ~ ~two
~ ~ highest occupied MOs of the cyclopentadienyl(trimethy1azete) cobalt
complex ( 5 , Me instead of tBu) can be described as linear
combinations of the la,(n*j and 2b1(n) of the azete with
the CpCo fragment (see Fig. 2, bottom and Table 1). As a
result of this interaction the electron density in the fourmembered ring of 5 is increased compared to 3. This explains why the bond lengths in the ring in 5 are found to
approach one another. In the PE spectrum of 5 (Fig. 2,
bottom), the ionizations from the two HOMOS are superposed by other bands which we ascribe to ionizations from
MOs that are strongly localized at the metal."61
I
14
13
z
#
HOMO ( 3 6 )
~ ~ [ e V j% C o
O,
co
6
MO
15
N
H O M 0 - 1 (351
Fig. 2. PE spectra of 3 (top) and 5 (bottom). x=count rate. The MOs associated with the bands are given below the two spectra.
The comparison of the PE spectra of 2 and 3 shows that
the position and shape of the bands involving the outer
valence electrons are very similar.['01This is best explained
in terms of the interaction between the mesityl and azete
moieties being very weak. The PE spectrum of 3 (Fig. 2,
top) shows two bands in the outer valency range (0
and
Angew. Chem. Int. Ed. Engl. 27 (1988) No. I1
Received: July 27, 1988 [Z 2889 IE]
German version: Angew. Chem. 100 (1988) 1616
16
CAS Registry numbers:
1, 117270-99-2; 2, 117271-00-8; 3, 103794-87-2; 4,69393-67-5; 5, 117308-54-0;
di-tert-buiylcyclopropenone,19985-79-6: mesiryllithium, 5806-59-7.
111 Review: H. Imgartinger, M. Nixdorf, N. H. Riegler, A. Krebs, H. Kimling, J. Pocklington, G. Maier, K.-D. Malsch, K. A. Schneider, Chem.
Ber. 121 (1988) 673.
121 U:J. Vogelbacher, M. Regitz, R. Mynott, Angew. Chem. 98 (1986) 835;
Angew. Chem. Int. Ed. Engf. 25 (1986) 842.
131 The azide was obtained as colorless crystals (m.p. 88°C) by reaction of
di-terr-butylcyclopropenonewith mesityllithium in ether at 0°C and subsequent reaction with hydrazoic acid. IR (KBr): 6=2100 c m - ' (N,);' H
NMR (90 MHz, CDC13): 6=0.92, 1.23 (each s, slightly broadened, each
9 H, tBu): 2.29, 2.41 (each s, 3 H and 6 H resp., mesityl-Me), 6.90 (s, arene-H).
141 K. Jonas, E. Defense, D. Habermann, Angew. Chem. 95 (1983) 729; Angew. Chem. Int. Ed. Engl. 22 (1983) 716.
151 5 : 'H NMR (200 MHz, [D&oluene): 6 = 1.18, 1.23 (each s, 9 and 18 H,
rBu), 4.95 (s, 5 H , cyclopentadienyl-H); "C NMR (75.5 MHz, C6Db.
40°C): 6 ~ 2 9 . 9[S, C(CH&-3], 30.5 [q, 'J(C,H)= 125 Hz, C(CH3),-2,4],
32.1 14. 'J(C,H)=126 Hz, C(CH,)y3], 32.5 IS, C(CH&2,41, 80.0 [d,
'J(C,H)= 175 Hz, C5H5], 89.9 (s, C-3), 104.2 (s, C-2/C-4); MS (70 ev):
m/z=345 (M",17%).
[6] Review of cyclobutadiene-metal complexes: A. Efraty, Chem. Rev. 77
(1977) 691.
0 VCH Verlagsgesellschaft mbH. 0-6940 Weinheim. 1988
0570-0833/88/1111-1561$ 02.50/0
1561
A:
171 The standard value for C(sp2)-C(sp') single bonds is 1.47-1.48
D. R.
Lide, Telrahedron 17 (1962) 125.
[S] Further details of the crystal structure investigation are available on request from the Fachinformationszentrum Energie, Physik, Mathematik
GmbH, D-7514 Eggenstein-Leopoldshafen 2 (FRG), on quoting the depository number CSD-53 306, the names of the authors, and the journal
citation.
[9] L. T. J . Delbaere, M. N. G. James, N. Nakamura, S. Masamune, J. Am.
Chem. SOC.97 (1975) 1973.
[lo] Ionization energies [ e v and assignments 2 : 7.6 (n2, azete), 8.4 (n,, x2.
aryl), 8.9 (Sa,, azete), 10.6 (nl, azete); 3 : 7.5 [2b,, (n)], 8.7 p a , , (a)],10.7
[ lb, (n)];methyltri-(err-butylcyclobutadienecarboxylate(3, C-C02Me
instead of N): 7.1 (n2,cyclobutadiene), 8.8 (o),9.5 (n, ester).
[I I] Further resonances: 6=20.5, 21.2 (mesityl-CH3-2,6,4), 26.0, 28.5
(C(CH,),-2,3), 31.8, 36.7 (C(CH3)>.2,3), 128.1, 130.3, 136.8, 137.8 (areneC). Measurements at higher temperature are problematic, since the azete
dimerizes via the C N double bond; a colorless powder (m.p. 198°C (decamp.) is obtained.
[I21 At - I1O"C they appear-only slightly shifted-at 6=202.2, 140.9, and
150.0.
I131 We thank Prof. P uon R . Schleyer for a 3-21G-21G and 6-31G* calculation on unsubstituted azete.
[I41 See also D. M. P. Mingos, Adu. Organomel. Chem. I5 (1977) 33.
[IS] M. C. Bohm, R.Gleiter, 7Xeor. Chim. Acta 59 (1981) 127.
[I61 Ionization energies [ e v and assignment (No. of the MOs in Table 1) of
the bands 0-0
in the PE spectrum of 5 : 07.5 (29, 30, 34); @ 8.1 (36);
@ 8.9 (35); 09.5 ( 3 3 ) .
No
Me
C
N' '
CI-P
Me
/
1
1,N-Me
I'
N-Me
\I
+
lSiMe
A
- ClSiMe3
C
\O
L
I
for iodo- and chlorophosphanes.["I Because of the rapid
exchange of the axial and equatorial positions on the
NMR time scale at room temperature (pseudorotation),
only one doublet is observed for the 'H and I3C resonances of the methyl groups. The positions of the signals
in the 'H and I3C NMR spectra are similar to those for the
chloro derivative 1 .I7]
The structure of 2 was determined by X-ray structure
The molecule (Fig. 1, Table 1) displays the distorted trigonal-bipyramidal geometry typical of related
phosphorane~.[~I
As expected, the axial bonds P-N2 (176(1)
pm) and P-N4 (175(1) pm) are longer than the equatorial
4-Iod0-1,3,5,7-tetrarnethyl-1,3,5,7-tetraaza-41~phosphaspiroI3.3]heptane-2,6-dione: Synthesis and
Crystal Structure of the First Iodophosphorane**
By Johannes Breker, Peter G . Jones, Dietmar Stalke. and
Reinhard Schmutzler Ir
Dedicated to Professor Ernst Otto Fischer on the occassion
of his 70th birthday
The earlier described iodine-phosphorus compounds
containing phosphorus in the oxidation state 5 have been
shown by electrical conductivity measurements11.21to be
phosphonium iodides with tetracoordinated phosphorus.
A report on a stable iodophosphorane formed by oxidation of triethyl phosphite with iodinel3] has meanwhile
been retracted.I4l The crystal structure analysis151of a I : 1
adduct obtained on reaction of tri-tert-butylphosphane
with iodine revealed a linear arrangement of the P-1-1
structural unit with tetracoordinated phosphorus. This
geometry represents a structural alternative to the earlier
undissociated precursor R3PIZof phosphonium iodides R3PIeIQ. Here we describe the synthesis of
the first h5P iodophosphorane. The postulated pentacoordination of the P atom was confirmed by an X-ray structure analysis.
The phosphorane 1, whose C1 atom has already been
exchanged for other s u b s t i t u e n t ~ is
, ~a~readily
~ ~ ~ accessible
compound containing a pentacoordinated P atom. Indeed,
the synthesis of the iodophosphorane 2 from 1 was accomplished by CIA exchange with ISiMe3['] in benzene.
Crystals of 2'Io1(correct elemental analysis), which are
pale yellow at -3O"C, are pale brown at room temperature. The "P NMR signal of the iodophosphorane 2
(6= - 119.1) is markedly shifted upfield compared with
that of 1 ; this is in agreement with the findings reported
[*I
[**I
Prof. Dr. R. Schmutzler, Dr. J. Breker
lnstitut fur Anorganische und Analytische Chemie
der Technischen Universitat
Hagenring 30, D-3300 Braunschweig (FRG)
Prof. Dr. P. G. Jones, Dr. D. Stalke
Institut fiir Anorganische Chemie der Universitat
Tammannstrasse 4, D-3400 Gottingen (FRG)
This work was supported by the Fonds der Chemischen Industrie.
1562
0 VCH Verlagsgesellschafl mbH, 0-6940 Weinheim. 1988
Fig. I . Molecular structure of 2 (H atoms omitted) [12].
Table I. Bond lengths [pm] and angles ["I of 2
~
~
Bond lengths
I-P
P-N2
P-N4
N 1-C2
N2-C3
N3-C5
N4-C6
02-C
245.8(3)
176.0(9)
175.3(10)
139.9(15)
143.9(18)
l41.6( 15)
l42.l( 16)
1 l8.6( 15)
P-Nl
P-N3
NI-CI
N2-C2
N3-C4
N4-C5
01-c2
167.0(8)
167.6(9)
143.9( 15)
139.7(14)
141.4(15)
l39.6( 15)
121.O( 12)
I14.7(4)
75.414)
133.0(4)
96.8(3)
166.3(5)
136.1(7)
128.0(8)
136.4(7)
137.6(8)
l27.6( 10)
138.8(9)
97.2(8)
13224 12)
I30.6( 11)
I-P-N2
I-P-N3
N2-P-N3
Nl-P-N4
N3-P-N4
P-NI-C2
P-N2-C2
C2-N2-C3
P-N3-C5
P-N4-C5
CS-N4-C6
N I-C2-01
N3-C5-N4
N4-C5-02
96.9(3)
I12.3(3)
98.5(5)
99.1(5)
75.9(5)
9537)
91.6(7)
123.7( 10)
94.6(7)
92.0(7)
124.0(9)
130.0(11)
97.3(9)
132.1(12)
Bond angles
I-P-Nl
NI-P-N2
NI-P-N3
I-P-N4
N2- P- N4
P-N 1-C 1
C I-Nl-C2
P-N2-C3
P-N3-C4
C4-N3-C5
P-N4-C6
NI-C2-N2
N2-C2-01
N3-C5-02
0570-0833/88/1111-1562 $ 02.50/0
Angew. Chem. Inr. Ed. Engl. 27 (1988) No. I 1
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