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Definite Proof of Spiroconjugation in [1.2]Spirenes

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[I51 H . J. Dauben, Jr. and D . J. Bertrlli, J. Amer. Chem. SOC. 83, 4659
(1961).
[I61 J. S. Waugh and R . W F e s s e n d w J. Amer. Chem. SOC. 79, 846
( 1957).
[I71 E . Sturm and K . Hafner, Angew. Chem. 76, 862 (1964): Angew.
Chem. internat. Edit. 3, 749 (1964): D . Muuche, M . Neuenschwander,
H . Schaftegger, and H . U . Schlunegger, Helv. Chim. Acta 47, 121 1 (1964).
[I81 R. Kaiser and K . Hafnrr, Angew. Chem. 82, 877 (1970);Angew.
Chem. internat. Edit. 9, 892 (1970).
[I91 G. Srhrodrr and J. F. M . Oth, Tetrahedron Lett. 1966, 4083; J .
F. M . 0 t h and J . - M . Gilles, ibid. 1968, 6259.
[20] H . Ginther, H . Srhmuckler, H . Konigshofm, K . Recker, and E .
Vogel, Angew. Chem. 85, 261 (1973):Angew. Chem. internat. Edit. 12,
243 ( 1973).
Definite Proof of Spiroconjugation in
[1.2]~pirenes[**l
By Heinz Durr, Bernd Ruge, and Heribert Schmitzf'l
Linkage of conjugated segments of polyenes (ribbond'])
via a formally sp3-hybridized C atom should lead to a
spirene exhibiting an interaction designated as spiroconjugationf2]. HMO['] and C N D 0 / 2 calculations[31 on
[ 1.2]spirene[**] predict stabilization of the H O M O by
interaction between the x ribbons while the energy of
the L U M O remains largely unaffected[', 'I. This should
result in a hypsochromic shift of the longest wavelength
UV band compared with that of the partially hydrogenated
system (7).
However, both electronic and steric substituent effects can
perturb the system and mask the spiroconjugation. Thus
the spirene (5c) provides no unequivocal evidence for
spiroconjugation[21, whereas ( 5 d ) and ( 5 e ) exhibit a
marked hypsochromic shift in the UV spectrum[4]. These
differing results prompted us to synthesize the alkyl-substituted [1.2]spirenes ( 3 a ) and ( 3 b ) in order to substantially
eliminate substituent effects.
R
R
Compounds ( 3 a ) and ( 3 b ) were prepared by irradiating
diazocyclopentadiene ( I ) in 2-butyne ( 2 a ) or 3-hexyne
( 2 b ) with long wave UV light (?i>360nm) until evolution
of nitrogen had ceased (cf. ref. IS]). ( 3 a ) and ( 3 b ) are
pale yellow oils (yield 47 and 35% respectively) which
decompose on attempted gas chromatography but could
be purified by chromatography and vacuum rnicrodistillation at room temperature.
The structure follows from the spectra. IR: ( 3 a ) : 1938;
( 3 6 ) : 1925 cm-' (cyclopropene stretching mode); NMR:
( 3 a ) : .r=3.8-4.0 (m) and 3.3-3.5 (m) (cyclopentadiene
H), 7.86 ppm ( s ) (CH,) (2:2:6); ( 3 b ) : ~=3.3-3.5 (m) and
3.7-3.9 (m) (cyclopentadiene H), 7.53 (4)(,J=7.5 Hz)
(CH,) and 8.95 ppm (t) (CH,) (2:2:4:6); mass spectrum:
( 3 b ) : m/e=146 (M+); UV, see Table 1. Further structural
proof comes from the Diels-Alder adducts of ( 3 a ) and
( 3 b) to tetracyanoethylene and to 2,3-dichloro-5,6-dicyano-I ,4-benzoquinone (cyclopropene band at 1860
to 1880 cm-I).
Table I. UVdatafor [l12]spirenes(3a)andf3b)andthe 5,s-disubstituted
cyclopentadienes ( 6 ) - ( 8 ) .
(30)
(3b)
(6)
(7)
(8)
methanol
methanol
isooctane
ethanol
ethanol
ethanol
239
24 I
242
250
257
254
I300
2450
2900
2880
2690
2750
The possibility of spiroconjugation was examined by comparison of the UV spectra of ( 3 a ) and ( 3 b ) with those
of (6)-(8)
which cannot show spiroconjugation. The
theoretically predicted hypsochromic shift['. 31 of the longest wavelength absorption band is indeed observed on
comparison of ( 3 a ) and ( 3 b ) with (8). It amounts to
12-1 5 nm, i. e. 5-6 kcal/mol.
While the UV spectra of spirotetraenes may be compared
with those of the corresponding saturated hydrocarbons[6.71,the method runs into difficulties with ( 3 n ) , ( 3 b ) ,
and ( 7 ) . The p orbitals (Wafsh model) of the cyclopropene
single bonds can enter into pseudoconjugation via the
sp2-hybridized spiro-C atom with the TI electrons of the
five-membered ring[*]. In ( 3 a ) and ( 3 h ) a hypsochromic
shift becomes operative due to spiroconjugation and a
bathochromic shift due to pseudoconjugation. Comparison
of (7) and ( 8 ) shows that the latter effect should result
in a bathochromic shift of the order of 3nm. In reality
the stabilization of ( 3 a) and ( 3 b ) will therefore be greater
than 5-6 kcal/mol. Spiroconjugation can thus be regarded
as established in [ 1.2lspirenes. Photoelectron spectroscopic
studies are currently in progress.
1,2-Diethylspiro[2.4]hepta-l,4,6-trirne ( 3 b ) .
A solution of ( I ) (4.0g, 43.5mmol) in ( 2 b ) (150ml) was
irradiated,after 15 minutes' purging with Nz,
with a Philips
HPK 125W lamp (GW, filter) for 4 h at 0°C. (6&70%
of the calculated amount of N Z was liberated.) Unreacted
( 2 b ) was then removed in cacuo and the blackish brown
residue rapidly chromatographed over silica gel ( I5Og)
with CH2C12.Chromatography with CC14 under the same
conditions afforded ( 3 b ) as a pale yellowish oil. Prior
to spectroscopy ( 3 b ) was distilled in a microapparatus
at room temperature.
Received: April 12, 1973,
supplemented: May 7, 1973 [Z 834 IE]
German version: Angew. Chem. X5, 616 (1973)
-
~~~
[*] Prof. Dr. H . Durr, Dip].-Chem. B. Ruge, and H. Schmitz
Institut fur organische Chemie der Universitat
66 Sdarbrucken (Germany)
[**I The parent compound of the [1.2]spirenes
is spiro[2.4]hepta-l,4,6-
triene.
Anyrw. Chrm.
intrrnur. Edit. f led 12 ( 1 9 7 3 ) N o . 7
[I]
M . J . Goldsrrm and R. Hoffmann, J. Amer. Chem. Sac 93, 6193
( 197 I).
121 H . E. Simmons and T Fukimaga, J. Amer. Chem. SOC. X Y , 5208
( I 967);R. Hoffmann, A. Imamirru, and G. D . Zriss, ihid. 89, 5 2 I5 ( 1967).
[3] A. Tujiri and T Nakujirna. Tetrahedron 27, 6089 (1971).
577
[4] H . Diirr and B. Ruyr, Liebigs Ann. Chem. /973, 214.
[5] H . Diirr and B. Ruye, Angew. Chem. 84, 215 (1972); Angew. Chem.
internat. Edit. 1 1 , 225 (1972); and earlier papers.
[6] R. Bosrhi, A. Dreiding, and E. Hrithronnvr, J. Amer. Chem. SOC.
92, 123 ( 1970).
[7] M. F. Srmmrlhack, J . S. Foos, and S. Katz, J. Amer. Chem. SOC.
94, 8637 (1972).
[8] W A. Bernetf, J. Chem. Educ. 44, 17 (1967).
Mesomolecules.
Polyaza-Polyoxa Macropolycyclic S y s t e m s [ * * ]
By Jean-Marie Lehn, Jacques Simon,and Joseph Wagner“]
The chemistry of molecular systems presents quite a clear
dichotomic separation into the micromolecules of organic
chemistry (M.W. < 500) and the macromolecules of
polymer chemistry and biochemistry (M.W. > 5000).
Although these definitions of size are arbitrary, it nevertheless appears that comparatively very few organic chemical
studies have been directed towards the design, the synthesis,
and the properties of molecules of intermediate size, i.e.
mesomolecules (not considering systems akin to natural
products like porphyrins, corrins, peptides, rtc.).
Such systems may present a multitude of new properties
compared to “small” molecules, by the mere token of
their size and the resulting palette of possible structural
variations, while also being challenging synthetic targets.
A number of macrocyclic[’], macrobicyclic[2-41, and macr o t r i c y c I i ~ ’ ~molecules
.~~
have been synthesized recently.
Many of them may act as ligands for the formation of
selective inclusion complexes[’.
- 8l
(“cryptates”)[’]
with various metal cations; natural macrocyclic peptides
and depsipeptides also form cation complexe~[~l;
macrocyclic polysugars, the cyclodextrins, are able to form molecular inclusion complexes[‘01.The common feature of these
systems, which are still of relatively small size, is the presence of a molecular cavity which confers upon them their
specific properties.
We preseyt here the synthesis of several macrotricyclic
and macrotetracyclic molecules. The intramolecular cavity
of these systems is appreciably larger than in the previously
reported cation ligands[” 3 . 4 . 6 1 ; thus, in addition to new
conformational and cation complexation properties, they
might be able to complex molecules, i.e. to function as
specific molecular receptors[ I41.
Monoprotection of the macrocyclic diamine ( 1 )[3a1 using
benzyl chloroformate in benzene (diamine: chloroformate= 1 : 1 ) gives compound (2) (viscous oil) in 50% yield[’’].
Condensation of (2) with the diacyl dichlorides ( 3 a ) ,
( 3 b ) [ ” l , and ( 3 c ) (m.p. 9 2 T ) affords respectively the
diamides (4a), ( 4 b ) , and ( 4 c ) , which are then converted
into ( j n ) , (Sb),and (Sc) with hydrogen bromidein acetic
acid (48%). Products ( 4 ) and (5) have not yet been
obtained in a crystalline form; the yields are about 90%
for the two steps.
The next step is performed under high dilution conditions
following a procedure very similar to the one used for
the synthesis of the previously described macrobicyclic
systernd31. Condensation of ( 5 0 ) . (.Sb). and ( 5 r ) with
the dichlorides ( 3 a ) , ( 3 b ) , and 1 3 ~ respectively
)
(in benzene and in the presence of thrcc equivalents of triethyl334,6
-
[*I
[“*I
578
Prof. J . . Lehn, J. Simon, and Dr. .I.
Wagner
lnstitut de Chimie, Universiti Louis Pasteur
I . rue Blaise Pascal, 67 Strasbourg (France)
ERA 265 du C.N.R.S.
Molecular Receptors, Part I .
(91, 2 = co
( l o } , Z = CH,
(a). Y = CH,;
(b), Y = 0; (c). Y = N T o s
amine) affords the macrotricyclic tetracarboxamides (6 a )
(m.p. 185-186°C; yield 75%), ( 6 b ) (m.p. 1 8 5 T ; yield
70%), and 6 c ) (m.p. 223°C; yield 55%). These tetraamides
(6) are reduced by diborane in tetrahydrof~ran[’~1
(reflux
for about 10 hours). Hydrolysis of the resulting products
with 6 N HCI (reflux for about 10 h) followed by passage
[ I ] C . J. Prdrrsen and H . K . Frensdorff, Angew. hem. 84, 16 (1972):
Angew. Chem. internat. Edit. 11, 16 (1972).
[2] H. E. Simmons and (’. H . Park, J. Amer. Chem. SOC.90, 2428 (1968).
[3] a) B. Dietrich, J . M . Lrhn, and J . P. Sauoagr, Tetrahedron Lett.
1969, 2885; b) Chem. Commun. 1970, 1055.
[4] J. M. Lrhn and F. Monracon, Tetrahedron Lett. 1972, 4557.
[S] H. E . Simon, C. H . Park, R . T U y d a , and M. F. Habibi, Trans.
N. Y. Acad. Sci. 32, 11, 521 (1970).
[6] J . Chrnry, J. M . Lrhn. J . P. Saucugr, and M . E . Strrbbs, J. C.
S . Chem. Commun. 1972, 1100.
[7] B Dirtrich, J . M . Lrhn, and J . P. Soucagr. Tetrahedron Lett. 1969,
2889.
[8] J. M Lehn, Struct. Bonding, in press.
[9] W E. Morfand W Simon, Helv. Chim. Acta 54, 2683 (1971).
[ 101 F. Cranirr. Einschlussverbindungen. Springer Verlag, Heidelberg
1954: F. Cramrr, W Sarnyer, and H.-Ch. Spatz, J. Amer. Chem. SOC.
NY, 14 (19671.
[ 1 I] R. Ansdtiitz and F. Birmaux, Liebigs. Ann. Chem. 273, 64 ( 1 890).
[ 121 The yield is almost quantitative when recovered ( I ) and diprotected
derivative (which may be hydrolyzed back to ( 1 ) ) are taken into account.
[I31 H. C. B r o w and P. Hrini, J. Amer. Chem. SOC.86, 3566 (1964).
[I41 J. M . Lrhn, J . Simon, and J . Wagiwr, Angew. Chem. 85, 622
(1973): Angew. Chem. internat. Edit. 12. 579 (19731.
Angrw. Chum. interifat. Edit.
1 Vol. 12 (1973) N o .
7
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