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Bridged Aza[10]annulenesЧ10-Analogues of Pyridine.

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tion. However, single crystals of Pd2Se13 were obtained on
reaction of Pd12 with Se in liquid iodine.
In the brass-yellow crystals of PdTeI, the Te and I atoms
are cubic close packed with Pd atoms occupying half of the
octahedral vacancies. There is a close relationship to the NaCl
type, which can also be substantiated by group theoretical
considerations. The PdTe2/214/4
octahedra are stretched along
the c axis (Pd-I 260 and 284, Pd-Te 284pm, each 2 x).
They are linked alternately via edges of two I and two Te
atoms to form chains. Since each I atom also represents the
apex of two octahedra from adjacent layers, a loose threedimensional network is formed (cf. Fig. 1). There are no covalent bonds between the Te and I atoms (closest contacts:
1-1 339, Te-Te 380, T e I 391pm), and the compound
should therefore be formulated as palladium(II1) telluride
iodide Pd3+Te2-I-. The stretching of the coordination octahedron around Pd3 can be explained as Jahn-Teller distortion
of a d7 low spin system. The diamagnetism, the good electrical
conductivity (specific resistance at 25°C: p = 4 x 10-4Qcm),
and the striking color of the compound suggest, however,
that the bonding can only be fully explained by the band
model.
+
b-
I/
ment of three I atoms and the Se atom of a Se2 group.
The Se:- group links four such squares to form Pd4SeZ1414,2
units (cf. Fig. 2), which in turn are linked via the four corners
to form puckered layers.
Procedure
Single crystals of PdTeI: Pd sponge (SOmg), Te powder
(60mg), I2 (120mg), and KI (30mg) are heated to 300°C
with 55 % HI solution (1ml) for 6 d in a glass ampoule of
ca. 4 ml capacity. The resulting brass-yellow crystalline needles
were filtered off and washed several times with hot water
(yield ca. 120mg).
Single crystals of PdzSe13: PdIz (30mg), Se (120mg), and
Iz (7.5g) are heated together to 250°C for 2d in a glass
ampoule, and the melt is slowly cooled (0.5"C/h) to just above
the melting point of iodine. Liquid iodine is decanted from
the precipitate within the ampoule; residual Iz can be removed
by repeated washing with acetone, and excess Se by heating
with conc. H2S04. Powder samples can be prepared more
easily by reaction of Pd (70mg), Se (52mg), and 1 2 (84mg)
in 1ml of 55 % HI solution.
X-ray structural data were recorded with MoK, radiation
between 3" and 25" in a single crystal diffractometer. 229
(PdTeI) and 324 (PdzSe13)independent data were employed
in the solution (program system SHELXr3I); refinement led
to R = 5.42 and 8.33 %, respectively.
Received: July 31, 1978 [Z 69 IE]
German version: Angew. Chem. 90, 897 (1978)
[l] J . Fenner, D. Mootz, J. Solid State Chem. 24, 367 (1978); I l . 1 ~ .Alpen,
J . Fenner, B. Predel, A. Rabenau, G. Schluckebier, 2. Anorg. Allg. Chem.
438, 5 (1978); P. M . Carkner, H. M. Haendler, J. Solid State Chem.
18, 183 (1976); references cited therein.
[2] A. Rabenau, H. Rau, Inorg. Synth. 14, 160 (1973).
[3] G. Sheldrick, University Chemical Laboratory, Cambridge UK 1976,
Cyber 172 Version by G. Zoubek, Erlangen.
@ Te
01
Fig. 1. Linkage of PdTe2121414
octahedra in the tetragonal unit cell of PdTel
[a=780.8(2), c=566.0(l)pm; space group P42/mmc; Z=4].
In the metallic black rhomboid crystals of Pd2Se13,however,
Pd is in the formal oxidation state of +2, since in the orthorhombic unit cell the Pd atoms are in a square-planar environ-
Bridged Aza[ 10]annulenes-l0~-Analogues of Pyridine[**]
By Maria Schiifer-Ridder, Arwed Wagner, Michael Schwamborn,
Helmut Schreiner, Eveline Devrout, and Emanuel Vogel"]
The potentially aromatic monoazaC4 n + 2lannulenes-the
homologues of pyridine-are still virtually unknown" - 31. In
view of the remote chance of being able to isolate simple
aza[10]- and aza[14]annulenes we concentrated our efforts
from the very beginning on the synthesis of the two bridged
aza[lO]annulenes, 2,7-methanoaza[IO]annulene (1) and 3,8methanoaza[lO]annulene (21, derived from 1,6-methano[lO]annulene. Though earlier attempts to prepare these
p]
Fig. 2. Pd4SeZ1414/zstructural units in PdzSe13 with principal distances and
angles. The orthorhombic unit cell [a=791.1(1). h= 1288.5(3),
c = 1432.1(3) pm; space group Pbca] contains 8 formula units.
Angew. Chem. Int. Ed. Engl. 17 (1978) N o . 11
Prof. Dr. E. Vogel, Dr. M. Schafer-Ridder, Dipl.-Chem. A. Wagner. Dipl.Chem. M. Schwamhorn, Dipl.-Chem. H. Schreiner, Dipl.-Chem. E. Devrout
Institut fur Organische Chemie der Universitat
Greinstrasse 4, D-5000 Koln 41 (Germany)
[**I This work was supported by the Ministerium Wr Wissenschaft und
Forschung des Landes Nordrhein-Westfalen (Germany).
853
novel heterocycles met without success[41,we have now found
routes to (1) and to a derivative of (2).
As starting compound for the synthesis of ( 1 ) we used
cycloheptatriene-1,6-dicarbaldehyde(3)15]. Reaction of ( 3 )
with methylene(tripheny1)phosphorane [prepared from
MePh3PBr and NaN(SiMe3)2] in the molar ratio 1 : 1.25 in
tetrahydrofuran (room temperature, 4 h) and subsequent chromatographic separation on silica gel (dichloromethane/hexane
1 : 1) afforded 6-vinyl-l,3,5-cycloheptatriene-l-carbaldehyde
(40 %), which on account of its sensitivity towards oxygen
was immediately oxidized with aqueous alkaline silver oxide
to the corresponding acid ( 4 ) [m. p. 1 16°C (from hexane);
yield 82%; 'H-NMR (CDCI3): 6=2.87 (s, 2H, H-7), 5.27
(d, 1H), 5.87 (d, 1H), 6.48 (m, 1H) (ABX system of the vinyl
protons), 6.2-7.0 (m, 3H, H-3, 4, 5), 7.43 (d, l H , H-2), 11.0
(br. s, 1 H, COOH); UV (cyclohexane): ilm,,=238nm
(E =33000), 292 (2650),343 (5000)]. The acid azide (5) formed
on reaction of the acid chloride of ( 4 ) with sodium azide
in aqueous acetone undergoes Curtius rearrangement on heating in toluene (1 I O T , 30min) to give 6-vinyl-l,3,5-~ycloheptatrienyl l-isocyanate(6), acompound isolableunder these conditions but prone to polymerize (b.p. 3O0C/O.1torr).
CON,
HO
I4 I
131
151
H
161
I81
OTs
191
111
The supposition that the isocyanate (6) could isomerize
thermally by a 10rr-electrocyclic process161-or by successive
cycloheptatriene-norcaradieneand Cope rearrangements' 71to the azaenone (7), and that (7) could readily be converted
prototropically into the thermodynamically more stable lactam ( 8 ) (2-azabicyclo[4.4.1]undeca-4,6,8,1O-tetraen-3-one)
has been confirmed experimentally: on heating ( 6 ) , or better
the acid azide (5), for 12 h in toluene the expected lactam
(8) is formed as main product [yellow needles, m. p. 143-144 "C
(from ethyl acetate); yield 35% based on ( 4 ) ; 'H-NMR
(CDCI,): 6=0.17 and 1.85 (AX system, J=9.6Hz, 2H, H-Il),
6.17 (d, J = 11.4 Hz, I H , H-4), 6.5-7.4 (m, 4H, H-7, 8, 9,
lo), 7.54 (d, J=11.4Hz, I H , H-5), 11.7 (br. s, I H , NH); UV
(acetonitrile): h,,,=223 nm (E = 12700), 270 (28800), 302
(4700), 373 (3500); IR (CHCl,): 3380, 1620cm-'].
Analogous to a-pyridone, (8) on reaction with trimethyloxonium tetrafluoroborate in dichloromethane (room temperature, 4 h) or on reaction of its silver salt with methyl iodide,
experiences almost exclusive 0-alkylation to lO-methoxy-2,7methanoaza[ 101annulene [bright yellow liquid, b.p. 6061 "C/O.l torr; yield 54 % and 55 %, resp.; 'H-NMR (CDC13):
6=0.22 and 0.4 (AB system, J=9.0Hz, 2H, H-ll), 4.0 (s,
3H, OCH,), 6.06 (d, J=10.2 Hz, I H , H-9), 6.7-7.3 (m, 4H,
H-3,4, 5, 6), 7.47 (d, J = 10.2 Hz, 1H, H-8); UV (cyclohexane):
hm,,=236nm (~=21500),264 (26000), 294 (sh, 5300), 372
(4700)], while with diazomethane a mixture of comparable
amounts of 0- and N-methylation products is obtained.
854
Attempts were made to accomplish the transformation of
(8) into ( I ) via the 0-tosyl derivative ( 9 ) [prepared from
the potassium salt of ( 8 ) and p-toluenesulfonyl chloride in
tetrahydrofuran (room temperature, 1 h), bright yellow needles,
m.p. 82-83°C (from methanol); yield 78x1. Reduction of
( 9 ) with two equivalents of lithium aluminum hydride in
boiling tetrahydrofuran (30min) afforded an unstable product
in which, according to 'H-NMR analysis, a mixture of dihydro
compounds of (1 ) was present. Consistent with this finding,
treatment of the original reaction mixture with 2,3-dichloro5,6-dicyano-p-benzoquinone (DDQ) (room temperature,
10min) led to dehydrogenation of the reduction product and
formation of a nitrogen base, which could be isolated in
pure form (yield 36-40%) by chromatographic filtration on
aluminum oxide followed by distillation. As confirmed spectroscopically, this compound, a stable yellow liquid of b.p.
63"C/1 torr and having a quinoline-like odor, is the desired
2,7-methanoaza[lO]annulene (1).
The most convincing evidence for the structure of ( 1 ) and
for its aromatic character is provided by the 'H-NMR
spectrum [90 MHz (CC14): 6 = -0.4 and 0.65 (AX system,
J = 8.4 Hz, 2 H, H-11b, and H-I larR1),
6.5 (dd, J = 9.0 and 6.3 Hz,
I H , H-9), 6.6-7.2 (m, 3H, H-4, 5, 6), 7.38 (two superposing
doublets, 2H, H-3, 8), 8.23 (d, J=6.3 Hz, 1H, H-lo)], for
it combines the characteristics of the spectra of a-substituted
1,6-methano[IO]annulenes and of pyridine and quinoline.
Striking similarities to the spectra of the 1,6-methano[lO]annulenes are seen not only in the position of the
resonances of annulene- and bridge-protons at low field and
high field, respectively, but also in the coupling constants
of the bridge protons [JH., l a , H-I I b = 8.4 Hz, Jl3c-1 H-, =
145 Hz (142 Hz in the case of 1,6-methano[IO]annulene)].
Very good agreement is also found in the absorption patterns
of the annulene protons of ( I ) and the quinoline protons;
however, in parallel with the findings in the pair 1,6-methano[lO]annulene/naphthalene, the resonances of the annulene
protons appear at higher field.-That (1) is to be regarded
as a heteroaromatic system is equally evident from the similarity of its UV spectrum [(cyclohexane): Lax
= 240 nm
(~=28300),258 (11 800), 297 (sh, 2650), 364 (2200)] with that
of 1,6-methano[lO]annulene; qualitative differences between
the two spectra, such as the increased extinction of the longwave Lb band in the azaannulene spectrum, correspond to
those observed between the naphthalene and the quinoline
spectrum.
The aza[lO]annulene ( I ) has a pK, value of 3.20 (20°C)
and is thus more weakly basic than pyridine or quinoline
(pK, = 5.23 and 4.94, respectively)[']; nevertheless, it forms
a stable hydrochloride with dry hydrogen chloride in ether.
1101
I111
I121
Parallel to the synthesis of (1) we tried to prepare the
isomeric 3,8-methanoaza[IO]annulene (2) starting from tricyclo[4.3.1 .O]deca-3-en-S-one oxime (I Oy4]. Beckmann rearrangement of (10) with phosphorus pentachloride in ether
Angew. Chem. I n t . Ed. Engl. 17 ( 1 9 7 8 ) N o . 1I
( O T , 5 h) led to the lactam ( 1 1 ) [m.p. 93-94°C; yield 48x1,
which, on addition of bromine in dichloromethane and subsequent dehydrohalogenation of the resulting dibromide (not
isolated) with 1,5-diazabicyclo[4.3.0]non-5-enein tetrahydrofuran (room temperature, 15 h), could be transformed into
the lactam ( I 2) present as the norcaradiene valence tautomer
[m. p. 128-129°C; yield 30%; 'H-NMR (CDCI,): 6 = -0.18
and 1.71 (AX system, J=4.2 Hz, 2H, H-ll), 2.71 (q,
J=17Hz, 2H, H-5), 3.44 (d, J=13Hz, l H , one H-2), 3.69
(dd, J = 13, and 5 Hz, 1H, one H-2), 5.8 (m, 4H, H-7, 8,
9, lo), 6.9 (br. s, 1 H, NH)].
(1 2) reacts with trimethyloxonium tetrafluoroborate in
dichloromethane (room temperature, 4 h) with formation of
the iminoether (13 j , also present as the norcaradiene valence
tautomer [b.p. 64-66"C/O.l torr; yield 50%; 'H-NMR
(CDCI3):6= -0.25and 1.44(AXsystem,J=4.2Hz,2H, H-ll),
2.52 (q, 5=17Hz, 2H, H-5), 3.53 (s, 3H, OCH3), 3.83 (q,
J = 16 Hz, 2 H, H-2), 5.92 (m, 4 H, H-7,8,9, lo)]. Dehydrogenation of ( 1 3 ) with DDQ in dioxane (room temperature, 1min)
led to a complex reaction mixture, from which lO-methoxy-3,8methanoazar 10]annulene ( I 4 ) could be isolated by chromatography on silica gel (ether/pentane 1:3) as a stable yellow
liquid of b.p. 62-63"C/0.1 torr (yield 4-8x) ['H-NMR
(CCI,): 6 = -0.14 and 0.37 (AX system, J=9.5Hz, 2H, H-ll),
3.86(s, 3H, OCH3), 5.90(s, l H , H-9), 6.66 and 7.28 (multiplet,
4H, H-4, 5, 6, 7), 7.46 (s, 1 H, H-2)].
The NMR spectrum of this 3,8-methanoaza[lO]annulene
derivative, which corresponds to that of the isomeric 10-methoxy-2,7-methanoaza[ lOlannulene, affords clear evidence of
this system also being aromatic' I 'I1.
Received: August 3, 1978 [ Z 68a IE]
German version: Angew. Chem. 90, 894 (1978)
CAS Registry numbers:
( 1 ) , 64183-86-4; ( 2 ) , 64183-85-3; ( 3 ) , 28172-94-3; (4), 68050-77-1; ( 5 ) ,
68050-78-2; ( 6 ) , 68050-79-3; ( 7 ) , 68050-80-6; ( 8 ) , 68050-81-7; ( S ) , silver
salt, 68050-82-8; (81, potassium salt, 68050-83-9; (91,68050-84-0; (10),6805085-1 ;(1 I ) , 68050-86-2; ( 1 2 ) , 67338-10-7; ( 1 3 ) , 68050-87-3; (14), 66910-93-8;
6-vinyl-l.3,5-cycloheptatriene-l-carbaldehyde,
68050-88-4; lO-methoxy-2,7methanoaza[lO]annulene, 68050-89-5
[I]
[2]
131
[4]
[5]
161
171
[XI
191
[lo]
The synthesis of i0-methoxy-2,7-methanoaza[lO]annulene by O-methylation of the lactam (8) was first reported by E. Vogel at the 3rd
International Symposium on Novel Aromatic Compounds (ISNA 3),
San Francisco (USA), August 1977.
An aromatic bridged monoaza[l4]annulene, trans-1,3-10h,lOc-tetramethyl-lOb,l Oc-dihydro-2-azapyrene has been described by !I Boekelhride and W Pepperdine, J. Am. Chem. Soc. 92, 3684 (1970).
For the synthesis of aza[41i + l]annulenes, which are to be regarded
as homologues of pyrrole, see A. G . Anastassiou, Pure Appl. Chem.
44, 691 (1975); G. Schroder, ibid. 4 4 , 925 (1975).
E. deCfeur, Diplomarbeit, Universitat Koln 1967.
E. Vogel, R. Feldmann, H . Diiwel, Tetrahedron Lett. 1970, 1941.
The analogous 6n-electrocyclic process, the thermal isomerization of
butadienyl-1-isocyanates to r-pyridones, has been reported: L. E. Overman, S . Tsuhoi, J. Am. Chem. Soc. 99, 2813 (1977); and references
cited therein.
Cf. also the Cope rearrangement of cis-2-vinylcyclopropyl isocyanate:
E . Vogel, R. Erb, G . Lenz, A. A. Bothner-By, Justus Liebigs Ann. Chem.
682, 1 (1965).
H - l l a corresponds to the proton above the carbocyclic ring segment;
assignment of the two bridge protons is based on long-range coupling.
A . Albert in A . R. Katritzky: Physical Methods in Heterocyclic Chemistry, Vol. 1. Academic Press, New York 1963, p. 65.
We decided to publish the investigations on (2) earlier than planned,
on learning that 10-ethoxy-3,8-methanoaza[IO]annulene has been synthesized independently by Muchowski et al. in almost the same way
as ( 1 4 ) ; H . J . Gob, J . M . Muchowski, M . L. Maddox, Angew. Chem.
90, 896 (1978); Angew. Chem. Int. Ed. Engl. 17. 855 (1978). Nore added
in pruof(0ctober 20, 1978): Meanwhile, it has come to our attention
that 10-methoxy-3,8-methanoaza[10]annulene ( 1 4 ) has also been
prepared G. K . Helmkamp's group (University of California, Riverside)
[I": J . Lipa, Diss. Abstr. Int. B 38 (9), 4243 (1978)l.
Anyew. Chem. In[. Ed. Engl. 17
(1978) No. I 1
10-Ethoxy-3,&methanoaza[10]annulene, a 1h-Electron Analogue of Pyridine [**I
By Hans-Jiitym Golz, Joseph M . Muchowski, and Michael
L. Maddox[*l
The synthesis of 1,6-methano[lO]annulene, a hydrocarbon
which contains a delocalized lh-electron system, was reported
almost 15 years ago by Vogel and Roth"]. In principle, it
should be possible to prepare analogues of this compound
where one or more heteroatoms participate in the establishment of a lh-system stabilized by resonance, and indeed,
three such compounds (1)-(3)
with potential 1h-systems
have been synthesized. Whereas the recently disclosed methanoaza[lO]annulene derivative ( I )['I possesses spectral properties consistent with those expected for an aromatic system,
(2) and (3) do not. Thus, (2) is best regarded as a fluxional
m ~ l e c u l e [ ~while
" ~ , (3) definitely exists in the norcaradiene
form[3b1.This publication describes the synthesis of the title
compound ( 8 ) , a methanoazar 101annulene derivativd4I,
whose skeleton is isomeric with that present in (1 ).
The 0-(p-toluenesulfonyl) oxime ( 4 ) (m. p. 115-1 170C)[51,
obtained from the corresponding known oxime[61 and ptoluenesulfonyl chloride, when heated (40"C, 3 d) in aqueous
dioxane in the presence of 2,6-dimethylpyridine, gave the products of Beckmann rearrangement ( 5 ) and fragmentation
(6) in 20-30 % and 17 % yields, respectively (Table 1). The
lactam ( 5 ) was converted with triethyloxonium tetrafluoroborate (CH2Cl2,room temperature, 5 d) into the cyclic imino
ether (7) which on dehydrogenation with dichlorodicyanoquinone (dioxane, room temperature, 0.5-2 h) gave 10-ethoxy3,8-methanoaza[lO)annulene ( 8 ) in 8.5-1 3.5 2,yield. Compound (8), a stable yellow oil, was isolated by preparative
thin-layer chromatography (hexane/ethyl acetate, 10 : 1, silica
gel). The UV spectrum of ( 8 ) (Table 1) is indicative of a
system with extended conjugation, while the low field 'HNMR signals of the OCH2- and perimeter-protons, in conjunction with the upfield shift of the hydrogens in the methano
bridge, are compatible with the existence of a ring current
in the 10-atom periphery. The proton-decoupled "C-NMR
['I
H. J. Golz, Dr. J . M. Muchowski ['I, M. L. Maddox
Syntex Research, Institute of Organic Chemistry
3401 Hillview Avenue, Palo Alto, California 94304 (USA)
['I Author to whom correspondence should be addressed.
I**]Contribution No. 515 from the Syntex Institute of Organic Chemistry.
855
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