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The Benzene Ring as Dienophile in an Intramolecular [4 + 2] Cycloaddition Degenerate Rearrangement of 7 8-Benzobicyclo[4.2

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Js.,=17.5Hz, 1 H ; H2'),3.47 (dd, JV,,=7.5Hz. Jg,,=l7.5Hz, 1 H ;
H2'),3.82(s,3H;-OCH3),3.95-4.10(m, lH;H3'),4.06-4.14(m,2H;
= 13 Hz, 1 H ;
H 5). 4.45-4.59 (m, 1 H ; H4), 4.53 (dd, J,,, =7.9Hz, Jscm
H 4 ) , 4.65 (dd, JY,,=7.5Hz, JEI,,,=I3Hz, 1 H ; H 4 ) . 5.16 (s, 2H; OCH,Ph), 6.80-6.88 (m, 3 H ; arene-H), 7.14-7.50 (m, 10H; arene-H);
I3C NMR (63 MHz, CDC13,25 "C): 6 = 37.70,38.64,39.13(-CH,Ph. C2'
and C3'), 55.00, 55.94, (C4 and - O m , ) , 66.31 (C-5), 71.23 (-OCH,Ph),
79.60(C4'), 112.20, 113.90, 120.40, 127.35, 127.50, 127.84, 128.47, 128.90,
129.28, 130.80, 134.96, 136.83, 148.31, 149.46 (arene-C), 153.30 (Cl'),
170.04(C2). IR(KBr):t[cm-'] = 1785vs, 1700%1550s;MS(SOeV):m/z
504 (2%, M ' ) , 457 (3), 281 (3). 238 (4), 91 (100, C,H:). 65 (5).
[7] Analytical data for (4S)-4-(3-hydroxy-4-methoxyphenyl)-2-pyrrolidone
I c : M.p. = 126°C; [a];' = - 36.7 ( c = 1.8 in chloroform); 'H NMR
(250 MHz, CDCI,, 2 5 ° C TMS): 6 = 2.47 (dd, J,,, = 9.4 Hz, Jse,=
- 2
a: R =
H.
c:
R
D. d:
R
CH3
in the degenerate rearrangement 1 a $ 3 a, which can be observed only in the substituted compounds lc, d.
A high-yielding synthesis for the already known hydrocarwas developed, which also gave access to targeted
16.5H~,lH;-CHHCO),2.70(dd,J,,,=8.4Hz,J,.,=16.5Hz,lH;-bon 1
CHHCO), 3.39 (dd, Julc
=7.5 Hz, JBEm
= 8.5 Hz, I H ; -CHHNH), 3.61
substituted derivatives (Scheme 1). Under irradiation buta-
(quint, J = 8 . 5 H z , 1 H ; H4), 3.72 (dd, JVi,=Jg,,=8.5Hz, 1 H ;
-CHHNH), 3.89 (s, 3 H;-OCH,), 5.94(s, lH;-NH),6.38 (s, 1 H;-PhOH),
6.69-6.86 (m. 3 H ; arene-H); "CNMR (63 MHz, DMSO, 25°C):
S = 37.93 (C5), 40.49 (C4), 48.80 (C3), 55.71 (-OCH,), 112.39, 114.12,
117.27, 135.60, 146.34, 146.54 (arene-C), 176.02 (-CO); IR (KBr):
3 [cm-'] = 3260br m, 1685vs, 1520% 1445111, 1295m, 1280m, 12401%
1055m, 1030m. MS (80eV); m/i 207 ( 5 5 % , M + ) , 150 (100). 135 (40).
[Sl D. Seebach, J. Golinski, Helv. Chirn. Acta 1981,65,1413- 1423; S. J. Blarer, W. B. Schweizer. D. Seehach, ibid. 1982, 65, 1637-1654.
[9] D. A. Evans in Asymmefric Synthesis Vul. 3 (Ed.: J. Morrison), Academic Press, New York. 1984, p. 1
[lo] H. E. Zimmerman, M. D. Traxler,J.Am. Chem. Soc. 1956,79,1920-1923.
[ l l ] D. A. Evans, J. Bartoli, T. L. Shih, J. A m . Chem. SOC.1981, 103, 21272129; D. A. Evans, E. B. Sjogren, J. Bartoli, R. L. Dow, Tetrahedron Leu.
1986,27,4957-4960; D. A. Evans, J. S. Clark, R. Metternich.V. J. Novak,
G. S. Sheppard, J. A m . Chem. Sor. 1990, 112, 866-868.
4
a: R = H. b
R = Br.
1 4
c: R = D, d:
)
4
t
R
-
CHI
Scheme 1. a) Benzene, hv (lamp Q 1200 Hanau), 140 h, 12%. b) CCI,, 1,3-di-
bromo-5,5-dimethylhydantoin,1.6 equiv, 80 "C, 2 h, 72%. c) Dimethylformamide, Zn, IOequiv, sonation, 7 h, 81 %. d) 1) THF, n-butyllithium,
The Benzene Ring as Dienophile in an
Intramolecular [4+ 21 Cycloaddition:
Degenerate Rearrangement of
7,8-Benzobicyclo[4.2.2Jdeca-2,4,7,9-tetraene**
1.1 equiv, -78"C, 10min;2)DZO,30equiv, -78"Cto2OUC,70%.e) 1 ) T H E
n-hutyllithium, 1.I equiv, - 78 "C, 10 min; 2) methyl iodide, 4 equiv, - 78 "C to
20"C, 20%.
By Wolfram Grimme,* Thomas Grommes,
Wolfgang R. Roth,* and Rolf Breuckmann
The R bonds of benzene rings can-at higher temperatures-participate in pericyclic reactions. Besides the wellknown Claisen rearrangement,"] a sigmatropic hydrogen
shift and several electrocyclic ring openings131involving
benzene x bonds have been described. Benzene also funcHere we retions as diene in some [4 + 21 cycl~additions.[~~
port the first case of a [4+2] cycloaddition in which one of
the R bonds of a benzene ring reacts as dien0phi1e.I~'
We chose an intramolecular cycloaddition for the investigation of the role of benzene as dienophile, because this
reaction proceeds even with weakly reactive dienophiles for
entropy reasons. Moreover, because the cycloaddition at the
benzene ring is endothermic and easily reversible, its detection requires a molecule which yields a Diels-Alder intermediate that can return to two different products.
The 7,8-benzobicyclo[4.2.2]deca-2,4,7,9-tetraene
1 a fulfills these prerequisites : The diene bridge is spatially close to
the benzene R bond of the bicycle, and the symmetrical
cycloadduct 2a can return to the aromatic state along two
paths (formation of l a or 3a). The intramolecular [4+2]
cycloaddition with participation of the benzene ring results
[*] Prof. Dr. W. Grimme, Dr. T. Grommes
[**I
872
Institut fur Organische Chemie der Universitat
Greinstrasse 4, D-W-5000 Koln 41 (FRG)
Prof. Dr. W. R. Roth, R. Breuckmann
Fakultat fur Chemie der Universitat
Postfach 102148, D-W-4630 Bochum 1 (FRG)
This work was supported by the Fonds der Chemischen Industrie.
VCH Verlagsgesellschu/t mhH, W-6940 Wrinheim, 1992
diene added to navhthalene o affa d the [4+ 41 cycloadduct
4,['1 which was doubly or triply brominated with 1,3-dibromo-5,5-dimethylhydantoinin the planarizable allylic positions. The 1:1 mixture of 5 a and 5b obtained was debrominated with zinc, and the products separated by flash
chromatography (silica gel, cyclohexane). After halogenmetal exchange with n-butyllithium, the bromide 1 b yielded
the bicycle l c , d deuterated or methylated in position 2 on
treatment with D,O or methyl iodide.
A prior investigation had shown that the thermolysis of 1 a
leads to cis-4 b,8 a-dihydrophenanthrene; 1' therefore the
attempt to detect the rearrangement 1 c e 3c had to be performed close to the activation threshold for this thermolysis.
Bicycle 1 c (97% D1) in the gas phase was heated to 235 "C
for 93 h, and the crude product was then dehyrogenated with
2,3-dichloro-5,6-dicyano-l,4-benzoquinone
(DDQ) in CCl,.
The excess DDQ was reduced with cyclohexa-1,4-diene, and
the product filtered through silica gel. Separation by gas
chromatography furnished the benzobicyclic isomers and
phenanthrene in the ratio 3: 1. The 'H NMR spectrum of the
benzobicyclic isomers revealed a 1: 1 mixture of 1 c and 3c
with 81 % D, deuteration. The [4+2]cycloaddition with the
benzene ring as dienophile therefore takes place under the
chosen conditions, and leads to the equilibrium distribution
of the marked isomers.
The phenanthrene obtained is 64 YOmonodeuterated according to the mass spectrometric analysis, and its 'H NMR
spectrum shows that 60 YOof the deuterium atoms are situated in positions 9 and 10. When the preequilibrium 1 c e 3c
is considered, these values are in accord with the previously
0570-0833/92j0707-0872$3.50+ .25/0
Angel<. Chem. In!.
Ed. EngI. 1992, 31, Nu. 7
proposed mechanism[*] for the formation of dihydrophenanthrene from l a , in which a 1,5-shift of the etheno
bridge is followed by electrocyclic ring opening and new ring
formation. This mechanism would yield, after subsequent
dehyrogenation, phenanthrene with 72 YOdeuteration (D&
in which half the deuterium atoms occupy positions 9 and 10.
The kinetic parameters of the rearrangement of the benzobicyclo[4.2.2]decatetraene skeleton were determined for the
1-methyl compound 3d from an analysis by gas chromatography. 3d was obtained analogously to 1 a, from butadiene
and 1-methylnaphthalene. The primary photoaddition occurs here at both rings of naphthalene, and when the synthesis sequence is complete, 3d must be separated from its 3'-positional isomer by gas chromatography. Important physical
data for the new compounds are collated in Table 1.
The activation parameters of the pertinent Diels-Alder
reaction were found for the gas-phase thermolysis in the
temperature range between 231 and 301 "C with already described apparatus and techniques."'] The simulated reaction
course of Scheme 2 was fitted to the data in Table 2 by using
a Simplex routine for the optimization.["'
Table 2. Data for the thermolysis of 3d.
~
T
I"C1
231.13
Id
6
X
Is1
1%1
1x1
r%i
1.317
19.126
46.013
50.472
1.575
16.151
27.064
32.766
42.120
1.822
14.316
23.633
39.144
46.637
2.215
10.827
23.199
39.797
47.797
52.494
55.291
3.115
17.449
31.069
44.399
50.486
54.249
55.379
0.551
6.299
16.180
18.302
0.722
5.488
9.358
11.540
15.302
0.661
5.282
8.863
15.366
18.882
0.793
4.106
9.075
16.267
19.852
22.617
24.669
1.235
7.300
13.622
20.372
24.073
27.347
29.313
2.110
13.767
21.232
25.460
28.897
30.641
3.520
19.631
27.507
31.328
34.123
36.204
6.340
27.560
34.202
37.857
0.000
0
21 900
82200
103800
240.27
Table 1. Some physical data for the compounds 1b-d, 3d, and 4a. 'HN M R
spectra at 80 (1 b,4a) or 300 M H z in CDCI,, "C NMR spectra at 75.5M H z in
CDCI,,Mass spectra at 70eV. Satisfactory elemental analyses were obtained
for 1 b. Id. and 3d.
t
0
8300
16700
22200
34200
251.63
0
3000
I b: M.p. 70°C;'HNMR:6 =7.26-6.98
(m,4H), 6.45-6.10(m, 2H), 5.98(m,
2H),5.57-5.13(m,1H),4.36(m,1H),3.89(m,1H);MS:m/z260(Me,B'Br,
5%), 258 (Ma.
79Br,6%), 179 (Me-Br,loo), 178 (Me-HBr,
86)
I c : M.p. 110°C;'HNMR:6 =7.21-7.05(AA'BB, 4H), 6.36-6.23
(m,1 H),
260.39
5.92(m. 2H), 5.68-5.59(m,2H),4.02-3.82
(m,2H);MS:mi? 181 (Me,
69%),
30)
180 (Me-H. IOO), 179 (MO-D. 90) 166 (M@-CH,,
I d : M.p. 67°C;'HN M R : 6 =7.25-7.10
(pseudo-AA'BB', 4H). 6.22-6.16
(m,
lH),6.00-5.88(m.2H),5.59-5.51 (m,2H),3.86-3.81(m,1H),3.7(m,1H),2.19
(d, 4J=1.3H~,
3H);" C N M R : 6=152.28,138.25,136.79,126.76,126.53,
125.58,123.33,122.61,120.91,119.33,45.69.39.83,29.21;MS:rnj? 194 (Ma,
5900
12900
18400
28%) 179 (Me-CH,,
loo), 128(C,,H8', 7)
271.23
3d: M.p. 90°C;'H NMR:6 =7.32-7.18
(m, 3H), 7.12-7.09
(m,1 H),6.35-6.28
(m,tH).5.89-5.82(m,2H),5.68-5.53(m,3H),3.91-3.89(m,lH),1.69(s,3H);
I3C NMR: 6 =149.04,141.26,140.37,135.55,128.99,126.77,126.56,125.77,
123.61,122.35,122.30,119.37,40.21,38.97,27.00;MS: m/z 194 (Me,
20%),
loo), 165 (Ma-C,H,, 63)
179 (M@-CH3.
4 a : M.p.115°C;'HNMR:6 =7.18 (AABB, 4H), 6.22(m, 2H), 5.07(m,
280.77
2H). 3.61(m, 2H), 2.76(m, 4H); MS:m / z 182 ( M e , 4%), 128 (C,,HBe,
100)
The advantage of determining the kinetics of the rearrangement 3d -+1 d by gas chromatography in the gas phase
is offset by the loss of degeneracy. The more complex course
of the reaction is shown in Scheme2. Of the methyl-cis-
290.73
0
1100
3100
7000
10500
13300
16900
0
900
2100
4200
6000
8500
10500
0
990
2090
3090
4190
5190
0
800
1600
2400
3200
4100
301.14
0
700
1400
2100
98.131
73.503
35.102
28.156
97.703
77.338
61.925
53.686
39.955
97.517
79.408
65.864
42.721
31.085
96.754
84.182
65.996
40.985
28.982
20.773
15.561
95.338
73.708
52.727
31.359
21.019
13.476
10.163
92.386
53.710
31.312
20.153
13.210
10.231
87.835
38.849
18.794
11.480
7.834
7.162
79.578
20.641
9.567
7.324
5.003
29.772
43.136
49.500
52.567
53.475
7.799
37.653
48.442
51.326
51.816
50.208
12.629
46.252
49.776
47.933
1.073
2.704
3.071
0.000
1.024
1.652
2.008
2.623
0.000
0.994
1.641
2.769
3.397
0.238
0.885
1.730
2.951
3.717
4 116
4.479
0.332
1.543
2.582
3.870
4.422
4.928
5.144
0.502
2.751
5.320
4.887
5.326
5.653
0.846
3.867
5.258
5.867
6.226
6.425
1.455
5.548
6.455
6.886
Since the analysis was performed only for 3d, the resulting
activation parameters in Table 3 have a statistical significance only for the reaction 3d + ld;["I the quoted errors
represent a 95 % confidence limit.
X
Table 3. Activation parameters for the thermal rearrangement of 3d and 1d in
the eas Dhase (see Scheme 2).
6
Scheme 2. Formation of the methyldihydrophenanthrene derivatives 6.
4 b,8 a-dihydrophenanthrene derivatives 6, the isomer sub-
stituted at position 9 or 10 forms over 50%; moreover, 3d
yields an unknown product X in small amounts. As the thermolysis of the starting compounds 3d and I d shows, 6 is
formed from both, whereas X is derived only from 3d.
Angen. Chem. Int. Ed. Engl. 1992, 31. No. 7
0 VCH
Reaction
E,
[kcalmol- '1
log A
AH* (265°C) A S * (265°C)
[kcalmol-'1
[calmol-' K-'1
3d - I d
ld-3d
3d - 6
ld-6
3d + X
41.2f 0.5
43.0
43.3
41.1
46.6
12.83t 0.2
12.81
13.28
11.20
13.85
40.1 0.5
41.9
42.2
40.0
45.5
Verlagsgesellcchaft mhH. W-6940 Weinheim, 1992
-3.0 0.9
-3.0
-0.9
- 10.4
1.7
0570-0833/92/0707-0873$3.50+.25/0
873
The activation parameters of Table 3 yield a Gibbs activation energy for the rearrangement 3 d + I d at 35 "C of
AG* = 41.1 kcalmol-'; they are valid for the rate-determining step of the reaction, the cycloaddition 3 d --* 2d . The
corresponding rearrangements in the parent compound bicyclo[4.2.2]decatetraene and some derivatives take place at
this temperature with Gibbs activation energies of 22.3 to
24.2 kcal mol- . [ I 3 ] Here the replacement of an olefinic
double bond by a n: bond of a benzene ring thus increases the
Gibbs activation energy by about 18 kcalmol-'. In earlier
investigations of pericyclic reactions, such an exchange led to
an increase of only about 11 kcalmol-'.[31 Apparently the
transition state to the strained cycloadduct 2 in the reaction
studied here lies very late on the reaction coordinate and is
reached only after substantial loss of resonance energy in the
benzene ring.
Received: February 12, 1992 [Z5181IE]
German version: Angew. Chem. 1992, 104, 867
CAS Registry numbers:
l a , 19660-93-6; Ib, 141510-09-0; Ic, 141510-10-3; I d , 141510-11-4, 3d,
141510-12-5; 4a, 141510-13-6, Sa, 141510-07-8; Sb, 141510-08-9; 6, 14151014-7
[ l ] L. Claisen. 0. Eisleb, Jumis Liebigs Ann. Chem. 1913, 401, 21-1 19; for a
review, see S. J. Rhoads, N. R. Raulins in Organrc Reactions, Vol. 22 (Ed.:
W. G. Dauben), Wiley, New York, 1974, p. 1-252.
[2] W. R. Roth, Tetrahedron Lett. 1964, 1009-1013.
(31 a) E. Vogel, D. Wendisch, W. R. Roth, Angew. Chem. 1964, 76, 432-433;
Angew. Chrm. In/. Ed. Engl. 1964,3, 442-443; b) W. Grimme, J. Lex, T.
Schmidt, ibid. 1987,99,3277-1279 and 1987,26,1268-1270; c) T. Grommes, Dissertation, Universitat Koln, 1991.
[4] a) R. G. Miller, M. Stiles, J. Am. Chem. Soc. 1963. 85. 1798-1800;
b) R. S. H. Liu, ibid. 1968, 90, 215-216; c) E. Ciganek, Tetruhedron Leu.
1967, 3321 -3325.
[5] The [4+2] cycloaddition of some electron-poor dienes to the central bond
of benzocyclopropene is known: a) S. Korte, Dissertation, Universitiit
Koln, 1968; b) J. C. Martin, J. M. Muchowski, J. Org. Chem. 1984, 49,
1040-1043; c) R. Neidlein, L. Tadesse, Helv. Chim. Acta 1988. 71, 249253.
[6] E. Vedejs, R. A. Shepherd, Terrahedron Lett. 1970, 3863-1864.
[7] K. Kraft, G. Koltzenburg, Tetrahedron Lett. 1967, 4723-4728.
[8] L. A. Paquette, J. C. Stowell, Tetrahedron Lett. 1970, 2259-2262.
[Y] E. Vedejs, Tetrahedron Lett. 1970, 4963-4966.
[lo] W. Grimme, L. Schumdchers, W. R. Roth, R. Breuckmann. Chem. Eer.
1981, 114, 3197-3208.
1111 S. N. Deming, S . L. Morgin, A n d . Chem. 1973, 45, 278A.
[12] J. A. Nelder, R. Mead, Compur. .l1965, 7, 308.
[13] a) R. T. Seidner, N. Nakatsuka, S. Masamune. Cun. J. Chenr. 1970, 48,
187-192; b) H. D. Carnardi, P. Hildenbraud, J. Richter, G. Schroder,
Justus Liebigs Ann. Chem. 1978, 2074-2087.
report here the dependence of the polymerization of sulfur
on the wavelength of irradiating light. A central, unprecedented observation, however, is that desorption of a thin
cyclooctasulfur layer is stimulated by light (1 = 255 nm) in
high vacuum. As a result of the observed dependence of
desorption rate on light intensity, a purely thermal desorption process at a wavelength of 255 nm can be rejected.
The sulfur layer (a' = 100 to 700 nm) was generated in a
to 1 x lo-' mbar) by
high-vacuum apparatus (p = 4 x
directing a beam of S, molecules onto a polycrystalline gold
surface ( T = + 20 to - 50 "C). This is a component of the
probe of the quartz microbalance that monitors the layer's
thickness.
The sulfur condenses as a supercooled liquid that precipitates in the form of
above - 35 2 "C, regardless of the substrate studied (quartz glass, corundum, gold,
stainless steel). Below this temperature a continuous film
forms because the supercooled sulfur melt is present as a
Previously glass transition temperatures for sulfur of
-29°C1'oJ and -30°C1''1 were reported.['*'
For the sulfur layer consisting of droplets, an activation
enthalpy of 68 kJmol- ' for the evaporation could be calculated from the dependence of the thermal desorption rate on
temperature (Ford and La Mer[131report an enthalpy of
evaporation of 78 kJmol-' for a supercooled sulfur melt).
Thermal desorption could not be observed below - 36 "C for
the continuous glasslike film.
For the droplet film (cf. [7,8]) light-induced desorption
was detected for the first time (Fig. 1). The wavelength dependence of this desorption was studied at 255, 328, 382,
436, 545, and 656 nm. The maximum desorption rate (calculated with refererence to the radiative power per surface
area) was found at 255 nm (see Experimental). Studies on
supercooled sulfur melts by UV spectroscopy were hitherto
unknown. Absorption measurements for S, in solution such
as those of Steudel et al.['41reveal a double maximum in the
range 250-280 nm.
0;
Photoselective Processes in Cyclooctasulfur
Layers : Desorption versus Polymerization**
tl
By Jens Geyer, Heinrich Stiilpnagel, and Klaus Rademann*
The photolysis of cyclooctasulfur has been studied at various temperatures and wavelengths. To the known photochemistry of sulfur under the influence of UV light in the
250-400 nm range belongs the appearance of sulfur radicals
during the irradiation and polymerization of S,.[' - 6 1 We
[*I
Priv. Doz. Dr. K. Rademanu, J. Geyer
FB 14, Physikalische Chemie der Universitat
Hans-Meerwein-Strasse, D-W-3550 Marburg (FRG)
H. Stiilpnagel
Max-Planck-Institut fur Quantenoptik
D-W-8046 Garching (FRG)
[**I This work was supported by the Deutsche Forschungsgemeinschaft and
the German-Israeli Foundation (GIF).
874
Q VCH Verlagsgeselischafi mbH. W-6940 Weinheim,1992
200
~
tz
600
j
i
t3t4
1000
1400
t[s]--
Fig. 1 . Growth of the film thickness d with time on adsorption and thermal/
light-induced desorption for a S , droplet film. 2. = 255 nm. substrate temperambar. Desorption rates: V,, = 61-10-3 nms-' beture = 0 ° C p = 4 x
nms-' during irradiation, V,, = 59 x
fore irradiation, V=215 x
lo--' rims-' after irradiation. t , : effusive molecular beam source opened, t,:
molecular beam source closed, t,: UV lamp on, I,: UV lamp off.
To solve the question whether the desorption of sulfur by
UV irradiation at 1 = 255 nm is a purely thermal phenomenon, the dependence of the rate of light-induced desorption on light intensity was investigated. If the influence of
the light is exclusively due to a warming of the sulfur film, the
dependence of the light-induced desorption rate (V,) on light
intensity should be described by Arrhenius's law; the relationship between light intensity and increase in temperature
0570-0833/9210707-0874 $3.50+ ,2510
Angex. Chem. Int. Ed. Engl. 1992, 31, No. 7
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