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New C8H10 Isomers 2-Methylenebicyclo[3.2.0]hept-6-ene and 3-Methylenetricyclo[4.1.0

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structed using idealized bond angles and distances similar to
those reported for certain related c ~ m p l e x e s [ ~ . ~ ~ .
Model calculated cell dimensions are a = 14.47 (la) [and
(lb)]and a = 20.26 (2). Inspection of these coplanar models reveals certain unrealistically short inter-bridging distances in ( l a ) (e.g. C5.. . . C5), as well as some constraint associated with the intra-bridging C2.--.C2distance in (2). In
the case of (Z), the constraint is either reduced or removed by
the change in relative orientation of the phenylene rings. The
established tendency of monomeric cations of type
Rh(CNR): to oligomerize via weak Rh' .. . .Rh' bonding interactionr2'may suggest the stacking of the two-dimensional
models ( I ) and (2) in an eclipsed
In the absence of suitable single crystals, powder X-ray
diffractometric traces of the new polymers (la), (lb),and (2)
were measured. Especially informative results were obtained
for (Ib) and (2). Both polymers have the space group P4; the
cell constants are a=15.42(6), c=3.21
and a=21.95(8),
c= 3.36 A, respectively. The powder diffraction data appear
to be consistent with the presence of a tetragonal
rhodium atoms in these polymers. The most intense reflection found in these traces has been assigned to the 110 rhodium-containing planes, whose spacings correspond to the distance of separation of the metal nuclei by the bridging unit
(10.91 and 15.49 A, respectively). Besides other hkO reflection~[~
] , trace also contained one reflection which was
assigned to:he 001 plane. Tbe Rh-Rh distances [d(OOI)] in
( l b ) (3.21 A) and (2) [3.36 A] are similar to those found in
dinuclear cationic complexes of the type [Rh2(CNAryl)8]Z+
(e-g., 3.19[21, 3.21C3] and 3.25 Ar3]),as well as in a related
rhodium polymer with colinear 1,4-diisocyanobenzene
bridging units (3.31 A)[51.
' 1, O R h
(CHzC12,50 ml) of [Rh(CO),Cl], (0.4 g, 1.03 mmol) at room
temperature. The dark green polycrystalline (la) formed
during this reaction in a quantitative yield (based on the Rh
reactant), was filtered off, washed with CH2ClZ(5 x 50 ml),
and then vacuum dried (80 "C/O.l torr). The polymers ( l b)
and (2) could be prepared utilizing essentially the same procedure. The complete elemental composition data of the new
polymers are consistent with their formulation as
[Rh(Bridge): C1- ' xH2Oln.
The powder X-ray diffractometric traces were obtained on
a Phillips Diffractometer using filtered Cu radiation and a
scan speed of 1O (20) minReceived April 9, 1980 [Z 526 IE]
German version Angew Chem Y2, 649 (1980)
[ I ] I. Ugi. Isonitrile Chemistry Academic Press. New York 1971.
[2] K . R. Mann, N . S. Lewis. R. M. Williams. H . B. Gray, J . G. Gordon I I , Inorg.
Chem. f7, 828 (1978).
131 H. Endres, N . Gotrstem, H J. Keller. R. Martin, Z . Naturforsch. B 34, 827
141 H Lipson. H . Sleep/e: Interpretation of X-ray Powder Diffraction Patterns.
Macmillan, London 1970
[ S ] A. Efrary, I . Feinsrein, F Frolow, L. Wuckerle. unpublished.
New C8HI0Isomers: 2-Methylenebicyclo[3.2.OJhept6-ene and 3-Methylenetricyclo[]heptaneThermal and Metal-Catalyzed Rearrangements'**]
By Dieter Hasselmann and Klaus Loosen['1
Strained small-ring hydrocarbons are of interest owing to
their reactivity as well as their spectroscopic and structural
properties'']. The bicyclic isomer (lb)'z"lof toluene undergoes thermal isomerization exclusively via rupture of the central bond to give 5-methylene-l,3-~yclohexadiene(3b),
which should also be accessible from its isomer (2b) having a
bicyclofl.l.O]butane structural unit. In contrast, methylenebicycloalkenes (4) are observed to undergo both structural
isomerization to methylenebicyclo[2.2.n]alkenes (5) and a
degenerate methylenecyclobutane
comparison with this behavior and with the hydrocarbons (6)
and (7) having an endocyclic double bond, the reactions of 2methylenebicyclo[3.2.0]hept-6-ene(la) and 3-methylenetri-
Fig. 2. d( 110) in the polymer Ilb): A: calculated for the model; B: determined experimentally.
The shortcomings associated with the model are resolved
in the real polymer (1b) by the small increase ( v 0.68 A) in
the bridge span of 2,4-diisocyanotoluene (see Fig. 2); this
corresponds to a v 0.71 displacement of the methylphenylene unit towards the 110 plane. In a presumed situation involving the presence of proximity related eclipsed 2,4-diisocyanotoluene units, the inter-bridgiag distances in the real
polymer ( l b ) (e.g., C6.. . C6 zs 3.64 A; CH3. .. . CH3v 4.90 A)
are estimated to be considerably longer compared with the
respective (e.g., = 1.54 and = 2.80 A) model derived terms.
The increase in the bridge span can be rationalized by the
non-idealized C-N-C(Rh)
and N-C-Rh
bond angles
(see Fig. 2).-The powder X-ray diffractometric trace of the
polymer ( l a ) deviates from the expected pattern of a tetragonal system; interpretation of this trace has not yet been
(a), n
1,3-Diisocyanobenzene (1.06 g, 8.28 mmol) dissolved in
CH2CIz(100 ml) was added dropwise into a stirred solution
0 Verrag Chemre, GmbH, 6940 Weinherm, 1980
2; ( b ) , n = 1
(Za), respectively, would appear particularly interestingc31.We now report on thermal and metalcatalyzed rearrangements of the CRHLO
isomers (la) and
Priv.-Doz. Dr. D. Hasselmann, Dr. K . Loosen
Abteilung fur Chemie der Universitat
Universitatsstrasse 150, D-4630 Bochum 1 (Germany)
Reorganizations of Strained Methylenecycloalkanes. Part 6. This work was
supported by the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie. We thank Prof. M . Chrisrl, Univenitat Wiirzburg, for communication of unpublished results.-Ref. [Zb] is to be regarded as Part 5.
$ 02.50/0
ArIgeW Chem. In1 Ed Engl 19 (1980) No. 8
( l a ) and (Za) were obtained by methylenation of the appropriate ketonesr4]with methylenetriphenylphosphorane in
dimethyl sulfoxide in 42 and 65% yield of the pure compounds after preparative gas chromat~graphy[~].
of structure is based on spectroscopic dataI5'], hydrogenation
(Pd/C) [(la) giving endo- and exo-2-methylbicyclo[3.2.0Jheptane(90: 10)L5",h1,
and (2a) giving cis- (24%) and
trans-1,4-dimethylcyclohexane(72%) and methylcycloheptane (4%)], and their rearrangements.
Thermolysis of ( l a ) in the stationary gas phase leads only
to the methylenecycloheptadienes (3a) and
which are
in equilibrium ((3a):(8) = 98.8 :1.2 at 198.6 "C) under the
reaction conditionsc6']. The temperature dependence of the
rate of the pressure-independent (0.1-7 mbar) monomolecular cycloreversion of ( l a ) can be described between 163 and
208 "C by the Arrhenius parameters listed in Table 1. In ( l a )
the exocyclic methylene substituent not only effects the expected lowering of activation energy (AEa= 7.7 kcal/mol) relative to the unsubstituted system (9)l7*],but also a lowering
relative to the certainly more strained compound (6a) with
endocyclic double bondsr7'] (AEa= 1.7 kcal/mol) (Table 1).
Table 1 Activation parameters
f 10)
i 2a)
f 91
E, [kcal/mol]
[s 'I
37.80 -t 0.16
33.41 k0.32
32.54 t 0.44
32.4 t 0.6
13.61 k0.08
12.48 t 0.23
f7 4
Solution [b]
Solution [c]
[a] 1 cal=4.184 J . [b] [D,]-Toluene/tetrarnethylethylenediamine. [c] Dimethyl
Two reaction pathways must be considered for the rearrangements (la)-+(3a)+ (8): (a) a disrotatory route, forbidden by orbital symmetry, in which rupture of the bridgehead
bond in the transition state profits more from formation of
the conjugated system than the less flexible species (6a);this
leads directly to (3a), which subsequently equilibrates with
(8) via 1,5-hydrogen shift; (b) conrotatory, symmetry-allowed
opening of (la) to give trans&- and/or &,trans-methylenecycloheptadienes [t,c-(3a) and c,t-(3a), respectively], which
relieve their considerable strain by direct trans-cis isomerization, initially giving (Sa), and/or by 1,5-hydrogen shift [conformationally preferred c,t-(3a)--* (8)]initially giving (8).Enhanced formation of (8) as compared with the equilibrium
Angew. Chem. I n ( . Ed. Engl. 19 (1980) No. 8
(3a)F? (8) at small conversions of (1a) can be taken as experimental evidence for participation of trans-cycloheptadienes181.
Thermolysis of the tricyclic compound (Za) in n-heptane
(123-153 "C) primarily gives only the monocyclic species
(la). Small amounts of (3a) and (8) are attributable to decomposition of (la). In the stationary gas phase (123173"C), the rate of consumption of (Za), which is pressure
independent between 0.1 and 5 mbar, is strictly of first order,
but only half as high as in solution. This behavior is describable with Arrhenius parameters (Table 1) which lie in the expected range compared with those of tricycloheptane (lO)lyhl
and tricycloheptene ( 7 ~ ) However,
~ ~ ~ ~ the
. product spectrum
is more complicated than that obtained in solution. In addition to (la), more (3a)+ (8) is formed than would be expected under the reaction conditions from the amount of ( l a )
formed; (3a) and (8) are apparently also formed directly
from (2a). For the same conversions of (Za), the product ratio
(la)/(3a)+ (8) decreases with falling pressure, e. g. p = 5
mbar+10-3 mbar: (la)/[(3a)-t (8)]= 10.0-tO.8 (7 h, 154°C).
The rate of consumption of (2a) is concomitantly reduced by
15%. Surprisingly, (ll)rrol
appears as an additional product,
accounting for up to 8% of the
In analogy to the thermolysis of other endo,endo'-bridged
the isomerization (24 +(la) can be regarded as a concerted [,2, + ,2,]-reaction to give c,t- and/or
t,c-(3a), which subsequently recyclize to (la). However, diradical processes involving rupture of the C2C7bond in (2a)
as the initial step also appear to be energetically attainable
(cf. 19'.']). The pressure-dependent enhanced formation of
(3a) in the gas phase could be due to reaction branching at
the stage of vibrationally excited c,t- or t,c-(3a) or (la). Purely thermal formation of (21) is less readily understood. In
doubly bridged bicyclo[1.1.O]butanes a similar thermal isomerization to transoid 1,3-butadienes has recently been interpreted in terms of a retro-carbene ring openingrr2].
a reaction pathway ( 2 a ) - + ( l l ) with participation of a carbene [rupture of the C2C7and the C r C 7bond in (2a)I and its
insertion into the C6-H bond should be relatively inaccessible from an energetic viewpoint.
An insight into the behavior of (2a) towards transition metalsl'C1is provided by the following results: silver(])-catalyzed
rearrangement (benzene, 25 "C) leads via a-cleavage1'"] exclusively to (3a). In contrast, on heating with copper(0) in
benzene (1.5 h, 110 "C) primarily P-rearrangement["] is observed, giving (11) (81%) together with (3a) (17%) and ( l a )
(2%). This behavior resembles that of benzvalene (7b): reaction with Ag' gives only benzene, that with Cu" only ful~eneI'~1.
Received: March 13. 1980 [Z 527 IE]
German version: Angew. Chern. 92. 651 (1980)
[I] a) A. Greenberg, J. F. Liebman: Strained Organic Molecules. Academic
Press. New York 1978; b) A . de Meijere, Angew. Chern. 91. 867 (1979); An-
0 Verlag Chemie, GmbH, 6940 Weinheim, 1980
I3C-NMR Spectroscopic Studies on ['3C]methylated
Bituminous Coal
gew. Chem. Int. Ed. Engl. 18. 809 (1979); c) K. C. Bishop, Chem Rev 76,
461 (1976).
[2] a) D. Hasselmann, K. Loosen, Angew. Chem. YO. 641 (1978); Angew Chem.
Int. Ed. Engl. 17. 606 (1978); b) D. Hasselmann. P.-J. Rising, Tetrahedron
Lett. 1979, 1745; c) D. Hasselmann, Angew. Chem 87. 252 (1975). Angew.
By Matthias W. Haenel, Richard Mynott, Klaus Niemann,
Udo-Burckhard Richter, and Lothar Schanne[*l
Chem Int. Ed. Engl. 14, 257 (1975): Tetrahedron Lett. 1972, 3465: 1973.
131 Photoisomerization of a multiply alkylated derivative of ( l a ) to the correspondingly substituted ( 2 4 has been described by J. Ipakrschi, Chem. Ber.
105, 1996 (1 972).
141 a) Bicyclo[3.2.0]hept-6-en-2-one:R. M. Coafes. K. Yano, 1. Am. Chem. Soc.
9.5, 2203 (1973). T Suensson, Chem. Scr. 3, 171 (1973); b) tricyclo[4. I .0.02.7]heptan-3-one:[3]: c) M. Christ/ and €. Bmnn also obtained ( l a )
and (2a) from these ketones ( M . Chrisfl, personal communication. Feb
[5] a ) All new compounds gave correct elemental analyses and/or molecular
weights; b) the structures given agree with the spectra. c) ( l a ) : 'H-NMR
(CCL): 6 = I 05-1.80 (m, 2H-4). 1.85-3.00 (m. 2H-3). 3.27 (m, H-5). 3.38
(m. H-I), 4.71 (m, 2H-8). 5.86 ( = s , H-6. 7); "C-NMR (CDCI,): 6=25.7 (t,
C-4). 3 0 4 (1, C-3). 48.6 (d, C-5). 53.2 (d, C-I). 106.3 ( t C-8).
138.8 (d, C-6.
71, 151.5 (s. C-2): IR (CCIJ: infer uiia 3120 (-CH), 3070 (- CH), 3040
(- CH), 1660 (C-=CH2), 1566 (C X), 893, 703 cm '; MS (70 eV): m /
e=106 (4%. M i ), 91 (100). 78 (69); (2a): 'H-NMR (CDCI,): 6 = 1.35-1.75
(m. 2H-S). 1.90-2.25 (m. H-1. 7. 4. 4). 245 (m. H-6), 2.82 (q, J = 3 Hz. H2), 4.68 (m. 2H-8); "C-NMR (CDCI,): 6=8.0 (d, Jc,=205 Hz, C-1. 7),
106.8(t.C-8). 146.1 ( s ,
C-3); IR (film): inter aliu 3070, 2995, 1643 (C -:CH2), 877, 705 cm I : MS
M ' ) . 9 1 (lW).78(61)
[6] a) The structures of (3a) and (8) were confirmed by independent synthesis;
(3a): L. A. Puquefre, R. P. Hensel, R. F Eizember, J. Org. Chem. 3X. 3257
(1973); (8)was accessible in low yield from 3.5-cycloheptadienone only by
treatment with CHLIJMg(Hg) [5b] (cf. D. Hasselmann. Chem. Ber. 107.
3486 (1974)); b) the hydrogen shift (8)-(3a) [1627"C: f,,,=10 min] was
faster than the rearrangement (Ia)+(3a) + (8): after >90% conversion of
( l a ) approx 1 % of the isomeric methylcycloheptatrienes are formed from
(3a) and (8)
[7) a) G. R. Branton, H. M. Frey, D C. Monrague, I . D. R. Sfevens, Trans. Faraday Soc. 62. 659 (1966); b) M. R Willcoff,€. Goerland. Tetrahedron Lett.
A prerequisite for the spectroscopic characterization of
coal by high-resolution NMR spectroscopy is the preparation of soluble coal derivatives largely retaining the original
structure[']. A mild chemical reaction meeting these requirements is reductive derivatization using the "blue solutions"
of solvated electrons formed by potassium at low temperature in oligomeric polyethylene glycol dimethyl ethersl2I.
Transfer of these electrons to bituminous coal and subsequent hydrolysis12"]or reaction with electrophiles such as dimethyl sulfate or methyl iodide[2b1affords reduced or reductively methylated coal derivatives, respectively, having high
pyridine solubilities in some cases.
In the coal skeleton, in which aromatic and hydroaromatic
moieties are cross-linked by aliphatic chainsI31, not only do
methylations of acidic structures and Birch-Hiickel reductions of arenes occur, but benzylic C-C bonds in diarylethane and diarylmethane structures are also cleaved, as demonstrated by quantitative IR spectroscopy on coal derivativesl2] and cleavage reactions on model compounds141.The
associated degradation of the coal macromolecules is apparently responsible for the enormous increase in pyridine solubility-e.g. from 12 to 75% on reductive methylation of one
bituminous coalIZhl.
Reductive methylation of a medium volatile bituminous
coal from the Ruhr coalfield (see Table 1) with [13C]methyl
iodide (90 mol-% I3C) gave a methylated coal derivative
Table I . Composition and normalized empirical formulas of the starting coal and the methylated coal [Westerholt mine, seam "Robert": 23.6% volatile matter, 4.1% ash,
0.7% water, 12% soluble in pyndine].
Starting coal
["C]methylated coal
Methylated coal
Composition [wt-%]
0 [a1
Empirical formula.
Methy1/100 C
[ bl
I .4 [c]
[a] Determined directly. [bJ From the H/C ratio. assuming that hydrogen is incorporated only by methylation. [c] Including pyrites. [d] By mass spectrometry after combustion to '3C02/'2C02:4.4 CHI per 1W C atoms.
[Sl The borderline case of both rotational nodes should have been reached with
(la); bicyclo[4.2.0]oct-7-ene undergoes conrotatory opening: J. J. Bloomfield, J. S. McConaghy, Jr., Tetrahedron Lett. 1969, 3719, 3723.
[9] a) K. B. Wiberg, G. Sreimies. Tetrahedron Lett. 1967, 1235; L. A. Paquerre,
S. E. Wilson, R. P. Henzel, G. R. Allen, Jr., J. Am. Chem. Soc 94, 7761
(1972); b) M. Chrisfl, U. Heinemann, W. Krisfof, ibid. 97, 2299 (1975); improved data for (10) ( M Chrisfl, personal communication, Feb. 1980); c) according to Dewar and Kirschner, there is no contradiction between a diradical intermediate and stereoselective product formation in the rearrangement
of bicyclo[l.l.O]butanes: M. J. S Dewar, S. Kirschner, ibid. 97. 2932
[lo] a) R. E Eenson, R. V. Lindsey, Jr., J. Am. Chem. Soc. 81,4250 (1959); W. J.
Bailey. R. Barcluy. Jr.. rbid. 81, 5393 (1959). b) we synthesized (11) in simpler manner by cleavage of its cyclopentadiene adduct [5a, b].
11 1) The results were obtained reproducibly without loss of material in two independent thermolysis apparatus; they were unaffected by a conditioning of
the thermolysis vessel. p-Xylene. the acid-rearrangement product of ( I I ) ,
was not formed. Treatment of (2a) with acids in solution at room temperature gave little (30) in addition to considerable polymerization.
I121 U. Szeimies-Seebach, G. Szeimies, M. Van Meerssche, G. Germain. J . - P Declercq, Nouv. J . Chim. 3. 357 (1979): U Szeimies-Seebach. G. Szeimies, J
Am. Chem. Soc. 100. 3966 (1978); U. Szeimres-Seebach, J. Harnisch, G.
Szeimres, M. Van Meerssche, G. Germain, J.-P. Declercq, Angew. Chem. 90,
904 (1978); Angew. Chem. Int. Ed. Engl. 17, 848 (1978).
1131 U. Burger, F. Mazenod. Tetrahedron Lett. 1976, 2885; 1977. 1757.
0 Veriag Chemie, GmbH, 6940 Weinheim, 1980
whose [ i3C]labeling and high pyridine solubility (74.4%) permitted an NMR study. As shown by the I3C/I2C isotope ratio, determined by mass spectrometry after combustion of a
sample to carbon dioxide, 4.4 methyl groups have been incorporated per 100 coal carbon atoms. The I3C-NMR spectrum shows, apart from the [D5]pyridine signals (6 = 149.9,
135.5, 123.5), strong peaks in the range 6 = 10-65, which, in
view of the high isotope enrichment, are essentially due only
to the incorporated ["Clmethyl groups (Fig. l a , expanded in
Fig. 2); this follows from a comparison with the I3C-NMR
spectrum of a correspondingly prepared coal derivative having natural isotopic abundance (Fig. Ib).
The spectrum (Fig. 2) provides information about the nature of the methyl groups introduced. The I3C-NMR spectra
Priv.-Doz. Dr. M. W. Haenel, Dr R Mynott, Dr. K. Niemann [**I, Ing. grad.
U.-B. Richter. and Dr. K. Schanne
Max-Planck-Institut fur Kohlenforschung
Kaiser-Wilhelm-Platz 1, D-4330 Miilheim a. d. Ruhr (Germany)
["I Permanent address: Rheinische Braunkohlenwerke AG, D-5000 Koin (Germany).
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Angew. Chem. Int. Ed. Engl. 19 (1980) No. 8
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methylenetricyclo, methylenebicyclo, ene, hept, isomers, c8h10, new
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