close

Вход

Забыли?

вход по аккаунту

?

Facile Hydrogenation of the Central Cyclohexatriene of Tris(benzocyclobutadieno)benzene Synthesis Structure and Thermal and Photochemical Isomerization of all-cis-Tris(benzocyclobuta)cyclohexane.

код для вставкиСкачать
ti3
C64
Fig. 2. The structure of 2 in the crystal. Selected bond lengths [A] and bond
angles r ] : Ga-P 2.388(1). P-Si 2.210(2), Ga-N8 2.139(4), Ga-Cl 1.982(4), P Ga-P 94.25(5), P-Ga-Cl 129.4(1), P-Ga-N8 119.1(1), Ga'-P-Ga 85.75(5), CaP-Si 125.21(6), Ga'-P-Si 114.56(6), Cl-Ga-N8 84.2(2), P-Ga-N8 119.1(1).
'H- and 13C{'HI-NMR spectra.161N o significant spectral
changes were detectable down to 78 "C.
The thermolysis of 2 has been examined by temperatureprogrammed EI and CI mass spectrometry. When the temperature of the sample is increased at 20 'C/minute, a cluster
of peaks appear at ca. 130 "C which are attributable to the
monomer, e.g. at 200 "C for C,,H,,69GaN,PSi, found
550.147365, calculated 550.148472. No peaks corresponding
to the dimer are evident at this temperature.
[7] Crystal structure data for 1 . C,H; C,8H2,CI,GaN,, triclinic, space group
PT (NO 2), Z = 2, a = 8.2851(3), b = 9.4420(3), c = 14.5120(5)A, u =
S5.505(3), /r =79.723(3), y = 63.981(3)", V = 1004(1)A',
@,ah,d =
1.361 gcm3, (CU,~,J. = 1.5418 A, g = 43.80cm-'), 2530 unique data collected (%/2%
scan technique, 2.0 2 28 5 110.0"),of which 2255 had I > 3a(I)
and were used for structure solution and refinement.-2. 2C,H,CH3:
C,,H,,Ga,N,P,Si,
triclinic, space group Pi (No. 2), Z = 1. u =
11.3298(8), b = 12.1100(7), c = 14.7970(9) A, u = 66.342(5), fi = 68.596(6),
y =77.947(5)" V = 1727(4) A', @..,.6 = 1.242 g/cm', (Cu,,, 2. = 1.5418 A,
g = 20.56 cm-'), 3411 unique data collected (%j2% scan technique,
2.0 2 2%2 110.0"),of which 3271 had I > 341) and were used for structure
solution and refinement. Both data sets were collected on an Enraf-Nonius
CAD 4 diffractometer at 293 K, and were corrected for Lorentz, polarization, crystal decay, and X-ray absorption (empirical P-scan method). Both
structures were solved by direct methods (SHELX 86). Refinement (fullmatrix, least-squares) gave R = 0.0512 and R , = 0.0544 for 1 and
R = 0.0418 and R, = 0.0457 for 2. Further details of the crystal structure
investigations can be obtained from the Fachinformationszentrum Karlsruhe, Gesellschaft fur wissenschafthch-techniscbe Information mbH D7514, Eggenstein-Leopoldshafen 2 (FRG), by quoting the depository number CSD-54759, the names of the authors, and the journal citation.
[8] A. H. Cowley, P. C. Knuppel, C. M. Nunn, OrgunometallicsR (1989) 2490.
~
Experimental
1 : A solution of 7.38 mmol of Li[2,6-(Me,NCH2),C,H3] [5]in 30 mL of toluene
was added dropwise to a cooled ( - 78 "C) solution of GaCI, (1.3 g, 7.38 mmol)
in 25 mL of toluene. The reaction mixture was allowed to warm to ambient
temperature, after which it was stirred for a further 24 h. Filtration, followed by
solvent evaporation, afforded a turbid liquid from which colorless crystals of 1
(m.p. 58 C) were obtained in 61 % yield by the addition of benzene. MS(E1,
70eV): 3 3 2 ( M e . 32.20%), 297(Me-C1, 8.76%), 289(Me-NMe,,42.14%).
191 (Me-GaCI,, 99.71%), 105 (GaCI, 26.32%). 58 (CH,NMe,, 100%).
2: A suspension of Li,PSiPh, was prepared by the addition of 1.8 mL of iBuLi
(1.7 M in pentane) to a cooled (-78 "C) suspension of Ph,SiPH, [S] (0.44 g,
1.5 mmol) in 25 mL of Et20. The stirred suspension was allowed to warm to
ambient temperature, following which it was added to the suspension of 1
(0.73 g. 1.5 mmol) in 25 mL of Et,O at -78 "C. The reaction mixture was
allowed to reach ambient temperature and stirring was continued for 3 h. After
filtration and concentration of the filtrate, colorless crystals of 2 (m.p. 234237 "C), formed in 43% yield by cooling to - 20°C. Compound 2 is soluble in
Et,O. T H F and toluene, but only slightly soluble in n-hexane.
Received: June 10, 1990 [Z 4021 IE]
German version: Angew. Chem. 102 (1990) 1169
[l] For a review, see A. H. Cowley, R. A. Jones Angew. Chem. 101 (1989) 1235;
Angew. Chem. I n / . Ed. Engl. 28 (1989) 1208.
[2] For representative examples, see P. Paetzold, Adv. Inorg. Chem. 31 (1987)
123; H. Noth, Angew. Chem. iOO(1988) 1664; Angew. Chem. h i . Ed. Engi.
27 (1988) 1603; K. M. Waggoner, H. Hope, P. P. Power, ibid. 100 (1988)
1765 and 27 (1988) 1699; P. B. Hitchcock, J. D. Smith, K. M. Thomas, J.
Chem. SOC.Dalton Trans. f976, 1433.
[3] A. H. Cowley, R. A. Jones, M. A. Mardones, unpublished.
[4] G. van Koten. J. Terheijden, J. A. M. van Beek, I. C. M. Wehman-Ooyevaar. R. Muller, C. H. Stam, Organomeralhcs 9 (1990) 903.
I51 G. van Koten, A. Leusink, J. G. Noltes, J Chem. SOC.D . 1970, 1107.
[61 'H NMR (300 MHz, 295 K, C,D,, TMS ext.): 1: 6 = 2.12 (s, 12H,
(CH,),N), 3.03 (s, 4 H , CH,N), 6.95 (m, 3H H-aryl). 2: b = 2.32 (s, 24H,
(CH,),N), 3 52 (s, 8H. CH,N), 7.20 (m, 18H, m +p-H, Si-Ph), 7.29 (m,
6H. m +p-H. Ga-aryl), 7.49 (m, 12H o-H, Si-Ph). '3C(1HJ NMR
(75.48 MHz, 295 K, C,D,, TMS ext.). 1. b = 46.0 ((CH,),N), 63.5 (CH,N),
124.7 (broad, C-Ga), 129.9 (p-C, Ga-aryl), 130.1 (m-C, Ga-aryl) 143.3 (0-C,
Ga-aryl). 2: 6 = 46.0 ((CH,),N), 66.1 (CH,N), 125.3 (broad, C-Ga), 127 6
(rn p-C, Ga-aryl), 128.9 (broad, 0-C, SiPh,), 136.2 (broad, C-Si), 144.8
(0-C. Ga-aryl). 'lP{lH} NMR (121.5 MHz 295 K, C,D,, 85% H,PO,
ext.). 2: 6 = - 205, s.
+
Angew. Chem. Inr. Ed. Engl. 29 (1990) No. 10
8
Facile Hydrogenation of the Central Cyclohexatriene
of Tris(benzocyc1obutadieno)benzene:
Synthesis, Structure, and
Thermal and Photochemical Isomerization of
all-cis-Tris(benzocyc1obuta)cyclohexane * *
By Debra L. Mohler, K . Peter C. Vollhardt,*
and Stefan Wolff
We describe the first chemical reaction of hydrocarbon
1,"l namely its facile and stereoselective hydrogenation to 2,
whose X-ray structural analysis reveals the presence of an
unusually bond-fixed, planar cyclohexane ring. The latter
undergoes stereospecific thermal retrocyclization exclusively
to the hexaene 3, a feature that, in conjunction with the
associated kinetic data, suggests the occurrence of an unprecedented all-disrotatory process!'] In contrast, irradiation of 2 effects the rearrangement to the new hydrocarbon
4 and, ultimately, phenanthrene and naphthalene, whereas 3
photoisomerizes to 5 (Scheme 1). The reported chemistry
expands significantly the range of the transformations recorded for the benzocyclobutene nucleus and the tribenzo(CH) ,-manifold.
The hydrogenation of 1 to 2a proceeded under extraordinarily mild conditions,[31 a finding ascribable to the high
degree of bond localization and strain in the system. On the
other hand, the 2,3,6,7,10,11-hexakis(trimethylsilyl) derivative of 1[11was inert even at elevated hydrogen pressures
(80 atm, THF, Pd-C).
The stereochemistry of 2a was first assigned on the basis
of its 'H-NMR spectrum, particularly the signal for the central ring hydrogens (a singlet at 6 = 4.19), the 13C-NMR
spectrum (4 lines) and the analogous behavior of the related
angular and linear [3]phenylene~.[~~
Because of its novelty
and unexpected chemistry (see below), and also for comparison with 1, an X-ray structural investigation was carried out
[*I Prof. Dr. K. P. C. Vollhardt, D. L. Mohler, Dr. S. Wolff
Department of Chemistry, University of California at Berkeley,
and the Materials and Chemical Sciences Division,
Lawrence Berkeley Laboratory, Berkeley, CA 94720 (USA)
[**I This work was supported by the Director, Ofice of Energy Research,
Office of Basic Energy Sciences, Materials Science Division of the U. S.
Department of Energy (Contact No. DE-AC03-76 SF 00098). S. W. acknowledges a Postdoktoranden-Stipendium of the Deutsche Forschungsgemeinschaft (1989-1990).
VCH Verlagsgeselischafi mbH. 0-6940 Weinheim, 1990
0570-OR3319011010-1151S 3.50f.2510
1151
5
a
87%
2a, R=H
Zb, R-D
d
1
45%
(-I@
/
'
\
4a,b
Scheme I . (a) H, or D, (1 atm), Pd-C, THF, 18 h; (b) C,D,, sealed tube,
125"C-16OoC; (c) Et,O, hv 254nm. - 2 2 T , 4.5 h; (d) Et,O, hv 254 nm,
- 2°C. 3.5 h
(Fig. l).I5]The central cyclohexane ring is planar, a geometry
enforced by the three fused benzocyclobutenes. The average
dihedral angle between the plane of the former and those of
the latter is 54.5", giving rise to a strongly cup-shaped molecule. Most remarkable are two features: 1) There is strong
bond alternation in the cyclohexane frame (CI-C2, 1.60 A;
C1-C2', 1.51 A), to a degree that is unprecedented,[,' and
2) the geometry of the benzene rings is changed very little
relative to those of its precursor l,[',7l both comparing well
to those of model benzocyclobutenes,181an aspect also reflected in the 'H- and I3C-NMR data. The first characteristic could be a trigger to the thermal chemistry of 2 (see
below), the second may further corroborate recent theoretical findings that o-effects play an important role in the
bond-fixation observed in 1 (and, presumably, other benzenoid hydrocarbons o f this type).[''
Hydrocarbon 2 may be viewed as a trishomolog of the
extensively investigated all-cis-tris-o-homobenzenes"O1 and
as being endowed with sufficient ring strain (> 100 kcal
mol- I)[' '1 to undergo an analogous retro-[2 2 + 2]cycloaddition unraveling the cyclohexane moiety. However, the
tenuous nature of this notion becomes apparent when one
considers that the benzofusion in 2 renders (a least strained)
disrotatory four-ring opening unfavorable on the basis of
orbital symmetry considerations,[' that any concerted path
may be inhibited by the development of the antiaromatic
circuit of a [12}annulene system, and that the saturated
debenzo relative of 2, cis-tris[2.2.2]-o-homobenzene
6, is stable to high temperatures, when it decomposes through radical intermediates to a complex mixture of products.[' 3d1
These caveats notwithstanding, on heating (C,D,, sealed
tube, 125-160 "C, several days), 2a was isomerized cleanly
and stereospecifically to 3a,[31following first order kinetics
[ A H * = 29.4(4.7) kcalmol-',AS* = - 12.7(11.3)calK-'
Figure I. ORTEP drawings of the top and side views of 2a. Ellipsoids are
scaled to represent the 50% probability surface and hydrogen atoms are given
as arbitrary small spheres. Selected bond lengths [A] and angles ["I: C1-C2
1.599(4), Cl-C2' 3.511(4), Cl-C3 1.516(3), C2-C8 1.526(3), C3-C4 1.393(4),
C3-C8 1.379(4), C4-C5 1.394(4), C5-C6 1.379(5), C6-C7 1.391(4), C7-C8
1.376(3); C2-Cl-C2' 119.8(2),C2-Cl-C3 85.6(2), Cl-C2-C8 86.0(2), C4-C5-C6
122.2(3),CS-C6-C7 121.9(2), C6-C7-C8 116.1(3), C2-C8-C3 93.5(2), C3-C8-C7
12232).
mol-'I. NMR, in particular, highlighted not only the symmetrical nature of the product but also its dissimilarity to the
corresponding E,E,E
including Jcir= 12 Hz for the
former vs. J,,,,, = 18 Hz for the latter (obtained from the
respective 13C-satellite 'H-NMR signals). The ease and
specifity of the formation of 3 a from 2a provide strong
evidence for the occurrence of a concerted, all-disrotatory
mechanism. For comparison, Table 1 summarizes the activation parameters of some model systems.
Table 1. Activation energies E, (kcal mol-') for thermal ring-opening reactions of
selected model compounds [a].
+
1152
0 VCH
Verlagsgesellsrhafi mhH. 0-6940 Weinheim, 1990
[a] Stereochemistry of the reaction indicated by subscripts
0570-0833f90fl0l0-l152$3.50+.25/0
Angew. Chem. I n l . Ed. Engl. 29 (1990) No. 10
Support for the two cornerstones of this claim was assembled as follows. Stereochemistry : 3 cannot be preceded by
one of its double bond isomers, as those with either E,E,E[I4]
or E,Z,Z configurationf2]are inert to the reaction conditions, while that containing the E,E,Z structure has been
convincingly demonstrated to furnish stable 5 through homo-Diels-Alder cycloaddition of the cis-n-bond to the other
two (see also
Concertedness: both directly competitive and independent kinetic runs, employing 2a and its
hexadeuterated relative 2b [k,(125 "C) = 3.1 1(+0.08) x
10-6 s- 1 ,. kD(125"C) = 1.98( k0.06) x 10-6s-1] revealed the
same wsecondary deuterium isotope effect of kH/kD(D6)
= 1.57! This figure translates into kH/kD(D,)= 1.08, the
same as that observed for concerted cyclobutene openings.[* The absence of any relatively long-lived intermediates was ascertained by transforming 2a into 3a in molten
cis-2-butenedioic anhydride (160 "C, 7 d) without change in
the outcome of the reaction.
In view of the above findings, one might (naively) expect
that photochemical activation of 2 would, by an all-conrotatory pathway (producing initially either or both of the E,E,E
or E,Z,Z isomers of 3) result in 5.1141However, upon photolysis of 2a (or 2b) with 254-nm UV lamps (Rayonet, Et,O,
- 2 "C, 3.5 h), 4a (or 4b) was formed in 45 % yield, together
with starting material (32 YO)and small amounts of phenanthrene (or 9,lO-dideuteriophenanthrene)and naphthalene
(or [D,]naphthalene, the position of the label was not ascertained). The new compound 4a was characterized by spect r o ~ c o p yand
~ ~ ]X-ray analysis (Fig. 2).[16]
''
W
W
Fig. 2. ORTEP drawing of 4a. Ellipsoids are scaled to represent the 50%
probability surface and hydrogen atoms are given as arbitrary small spheres.
Selected bond lengths [A] and angles ["I: C1-C2 1.351(5), Cl-C24 1.526(6),
C2-C3 1.512(6), C3-C4 1.542(6), C3-ClO 1.590(6), C4-C5 1.392(5), C4-C9
1.376(5), C5-C6 1.426(6), C6-C7 1.413(6), C7-C8 1.407(6), C8-C9 1.401(5),
C9-C10 1.539(5),ClO-Cll 1.527(5), Cll-C12 1.514(5), C11-C24 1.549(5), C12C17 1.38615). C17-Cl8 1.482(5), C18-C23 1.415(6), C23-C24 1.525(5); C2-ClC24 123.1(4). Cl-C2-C3 122.3(4), C2-C3-C4 112.9(3), C2-C3-C10 116.2(3),
C4-C3-C10 85.8(3), C3-C4-C5 142.3(4),C3-C4-C9 94.1(3), C5-C4-C9 123.6(4),
C4-C5-C6 114.8(4), C5-C6-C7 121.2(4), C6-C7-C8 122.6(4), C7-C8-C9
114.7(4), C4-C9-C8 123.1(4),C4-C9-C10 93.80). C8-C9-C10 143.1(4), C3-ClOC9 86.2(3). C3-CIO-Cll 113.9(3), C9-ClO-Cll 122.7(3), C10-Cll-Cl2
113.2(3), ClO-Cll-C24 113.8(3), C12-Cll-C24 109.2(3), C1 l-Cl2-Cl3
118.4(4). Cll-Cl2-Cl7 121.3(4), C12-Cl7-ClS 119.4(4), C17-Cl8-Cl9
12134). C17-ClX-C23 118.9(4), C18-C23-C24 117.8(4), C22-C23-C24
122.5(4), Cl-C24-Cll 110.6(3), Cl-C24-C23 113.3(4), Cll-C24-C23 110.9(3).
A control experiment revealed that irradiation of 3a with
254-nm UV lamps at - 22°C for 4.5 h leads to 5 almost
quantitatively. It is therefore clear that the photochemistry
of 2 is associated with a new mechanistic manifold.['41While
Angew. Chem. Int. Ed. Engl. 29 ( i 9 9 0 ) No. 10
0 VCH
delineation of its details are premature, there are topologically analogous transformations in the literature.[' 2b, 7 l
'3
Received: June 29, 1990 [Z 4046 IE]
German version: Angew. Chem. I02 (1990) 1200
[l] R. Diercks, K. P. C. Vollhardt, J Am. Chem. Soc. 108 (1986) 3150.
[2] The conversion of 1 into 2a and subsequently 3 a was first communicated
April 6, 1987, at the 193rd ACS National Meeting (April 5-10, 1987).
Denver, Colorado. While this work was in progress. an alternative synthesis of 2a and its thermal conversion into 3a was reported, lacking, however, the essential structural and mechanistic and photochemical studies
delineated here: M. Iyoda, Y Kuwatani, T. Yamauchi, M. Oda, J. Chem.
Soc. Chem. Commun. 1988, 65.
[3] All compounds gave satisfactory analytical and spectral data. For example, 2a: colorless crystals, m.p. 192-195°C; MS (70eV): m / z 306 ( M e ,
100). 305(86), 191(61); 'H NMR (250 MHz, CDCI,): 6 = 4.19 ( s , 6H).
6.84 (AAm, 6H), 6.92 (BBm, 6H); '3C NMR (75 MHz, CDCI,):
6=40.6,123.7,126.4,147.2;IR(KBr):J=2930,1455,1210, IllOcm-I;
UV (hexane) A,, (log e) = 268 (3.27), 274 (3.24) nm. 2 b: MS (70 eV): m / z
312 ( M e , 84), 311(63), 194(72). 3a: colorless crystals, m.p. 185-186 'C;
MS (70 eV): m / z 306 ( M e , 100). 305(52), 191(55); 'H NMR (250 MHz,
C,D,): 6 = 6.56 (s, 6H), 6.77 (AA'm, 6H), 7.08 (BBm, 6H); "C NMR
(75 MHz, C,D,): 6 = 126.1,130.1,132.5,136.6; IR (KBr): J = 2990.2920.
1460, 1440, 1260, 1085, 800, 740, 650cm-'; UV (hexane): E.,,, (log
e) = 218 (4.43). 268 (3.43) nm. 3b: MS (70eV): m / z 312 ( M e ,
100). 4a.
colorless crystals, m.p. 145-147°C; MS (70 eV): m / z 306 ( M e ,
70), 305
(47), 178 (loo), 128 (75); 'H NMR (400 MHz, CDCI,): 6 = 3.24 (dd,
J = 5 . 8 , 5.8Hz. l H ) , 3.81 (dd. J=6.2,6.2Hz, IH), 3.87(dd. J = 5 . 3 ,
5.3 Hz, 1 H), 4.03 (dd, J = 5.2, 5.2 Hz, 1H), 5.96 (dd, J =7.4, 1 Hz, 1 H),
6.37 (dd, J = 10.1,6.7 Hz, 1H), 6.44 (dd, J = 10.1, 5.5 Hz. 1 H), 6.48 (ddd,
J =7.4, 7.4, 2 Hz, 1 H), 6.70-6.80 (m, 2H), 6.99 (dddd, J =7.0, 7.0, 2,
l H z , l H ) , 7.29-7.41 (m. 3H). 7.55 (bd, J = 7 . 7 H z , l H ) , 7.84 (bd.
J =7.4 HZ, 1 HI. 13cNMR (100 M H ~CDCI,)
,
6 = 36.86, 41.59. 42.61,
46.82, 120.08, 123.09, 123.42, 123.51, 125.70, 126.03, 126.24, 126.53,
127.23, 127.36, 127.65, 128.88, 129.25, 129.72, 133.70, 134.56, 138.01,
138.35, 145.83, 146.15; IR (KBr): J = 3063. 3028, 2913, 2838, 1482, 1450.
1243, 747cm-'; UV (hexane): I.,, (loge) = 234 sh (3.13), 269 (3.12). 305
(2.65) nm.
[4] a) B. C. Berris, G. H. Hovakeemian, Y.-H. Lai, H. Mestdagh. K. P. C.
Vollhardt, J Am. Chem. So<. 107 (1985) 5670; b) R. Diercks. K. P. C.
Vollhardt, Angew. Chem. 98 (1986) 268; Angew. Chem. Int. Ed. En$ 25
(1986) 266.
[5] Crystal size 0.19 x 0.22 x 0.27 mm3, trigonal Laue symmetry, space group
R3, 20 scan range 3"-45", u = 14.9760(18) A, h = 14.9760(18) A. c =
6.1680(6)A,~i=90.0",/3=90.0",~=120.0",V=1198.0(4)A3,Z=3,
ersicd= 1.27 gcm-',p = 0.7 cm-I, reflectionscollected at room temperature, 1034, of which 346 were taken as observed [P> 3a(FZ)],without
absorption correction, R = 0.0395, R, = 0.0556. Hydrogen atoms were
assigned idealized locations. The ideal positions of the hydrogens on the
strained carbons were adjusted based on residual peaks in the difference
Fourier map during the last cycles of refinement [18].
[6] G . McMullen, M. Lutterbeck, H. Fritz, H. Prinzbach, C. Kriiger. Dr. J.
Chem. 22 (1982) 19.
[7] We are juxtaposing the X-ray structural features of 2a to those of hexasilylated 1. The(min0r)perturbation caused by the substituentsin thelatter
can be assessed by comparing the analogous data for 4,5-bis(trimethylsilyl)-l,2-dihydrocyclobutabenzene[K. P. Moder, E. N. Duesler, N. J.
Leonard, Acfu Crystallogr. B 37 (1981) 2891 with those for 1.2-dihydrocyclobutabenzene IS].
[XI R. Boese, D. Bliser, Angew. Chem. 100 (1988) 293; Angew. Chem. Int. Ed.
Engl. 27 (1988) 304.
191 A. Stanger, K. P. C. Vollhardt, 1 Org. Chem. 53 (1988) 4889.
[lo] a) W-D. Braschwitz, T. Otten, C. Riicker, H. Fritz, H. Prinzbach, Angew.
Chem. 101 (1989) 1383; Angew. Chem. Int. Ed. Engl. 28 (1989) 1348;
b) D:R. Handreck, D. Hunkler, H. Prinzbach, ibid. 101 (1989) 1386 and
28 (1989) 1351, and references cited therein.
[ l l ] a) W. R. Roth, M. Biermann, H. Dekker, R. Jochems, C. Mosselman, H.
Hermann, Chem. Ber. 111 (1978) 3892; b) W. R. Roth, B. P. Scholz, ihrd.
114 (1981) 3741.
1121 a) J. F. Liebman, A. Greenberg: SfrucfureandReacfrvify,VCH Publishers,
New York 1988; b) J. J. Gajewski: Hydrocarbon Thermal Isomerizutions.
Academic Press, New York 1981;c) A. Greenberg, J. F. Liebman: Struined
Organic Molecules, Academic Press, New York 1978.
[13] a) R. Srinivasan, J. Am. Chem. Soc. 91 (1969) 7557; b) D. S . Weiss, Tetruhedron L e f t . 197s. 4001 ;c) F. v. Rantwijk. H. v. Bekkum, ihid. 1976,3341;
d) M. Maas, M. Lutterbeck, D. Hunkler, H. Prinzbach, Terrahedron Letr.
24 (1983) 2143; e) B. Zipperer, K.-H. Miiller, B. Gallenkamp. R. Hildebrand, M. Fletschinger, D. Burger, M. Pillat, D. Hunkler, L. Knothe. H.
Fritz, H. Prinzbach Chem. Ber 121 (1988) 757.
Verlagsgeselischafi mbH. 0-6940 Weinheim, 1990
0570-0833/90/1010-1153 3 3 . 5 0 i .2S/0
1153
[14] a) M. W. Tausch, M. Ehan, A. Bucur, E. Cioranescu, Chem. Ber. 110
(1977) 1744; b) H. A. Staab, F. Graf, K. Doerner, A. Nissen, Chem. Em.
104 (1971) 1159.
[I 51 a) J. J. Gajewski in E. Buncel, C. C. Lee (Eds): Isotopes in Organic Chemutry. Secondary and Solvent Isotope Eflects, Vol. 7, Elsevier, New York 1987.
pp. 160-162; b) see also: J. J. Gajewski, K. B. Peterson, J. R. Kagel,
Y C. J. Huang, J. A m . Chem. SOC.flf (1989) 9078.
[16] Crystals dimensions 0.25 x 0.30 x 0.40 mm3, orthogonal Laue symmetry,
space group Phca, 20 scan range 3'-45", a = 7.522(2) A, b = 15.009(3) A,
c = 28.858(7) A, 1 = 90.0", B
, = 90.0'. I; = 90.0, V = 3257.7(23)A3,
Z = 8, @c.,rd = 1.2Sg cm-3, p = 0.7 cm-', reflections collected at room
temperature, 2474, of which 1312 were taken as observed [F2 > 3u(F2)].
without absorption correction, R = 0.104, R, = 0.123[18]
[17] G. I. Fray, R. G. Saxton: The Chemi.stry of C.vclooctate!raene and Its
Derivatives, Cambridge University Press, New York 1978; J. D. Coyle
(Ed.): Phoiochemistry in Organic Synihesi.7. The Royal Society of Chemistry, London 1986. See also: J. J. McCullough, Acr. Chem. Res. 13 (1980)
270.
[18] Further details of the crystal structure investigation may be obtained from
the Fachinformationszentrum Karlsruhe, Gesellschaft fur wissenschaftlich-technische Information mbH, D-7514 Eggenstein-Leopoldshafen 2
(FRG), on quoting the depository number CSD-54806, the names of the
authors, and the journal citation.
i
-0
0
-
Structure of a Synthetic Trefoil Knot Coordinated to
Two Copper(r) Centers **
By Christiane 0. Dietrich-Buchecker, Jean Guilhem,
Claudine Pascard,* and Jean-Pierre Sauvage *
Although knotted forms of DNA are relatively common,
as shown by recent results of molecular biology,['. ' 1 knotted
compounds in chemistry have only been envisaged and discussed as hypothetical object^.[^-^]. A year ago, the first
synthetic trefoil knot was reported.'61 The preparation of this
topologically novel molecular system was made possible by
the use of a double three-dimensional template effect. Two
coordinating molecular threads were interlaced on two copper(r) centers, forming a double helix, the precursor of a
knotted system.
Although convincing evidence for the knotted topology of
the molecule was obtained from mass and 'H-NMR studies,
in particular by taking advantage of the chirality of a trefoil
knot, it was of utmost importance to obtain an X-ray structure of the molecule. In the meantime this has been achieved,
and we now report the molecular structure of the compound.
This study removes the last uncertainty regarding the knotted structure of the molecule obtained. It also provides interesting data on the fine structure and conformation. Moreover, it demonstrates that the knotted compound undergoes
spontaneous resolution, which is very encouraging for a future separation into right- and left-knotted enanti~mers.[~j
The chemical representation of the molecule is given in
Figure 1. The organic skeleton is made up of a single 86membered molecular chain, whose ends are tied with formation of a trefoil knot. The molecule still contains the two
copper([) centers used as templating species during the synthesis.
[*] Dr. C. Pascard, Dr. J. Guilhem
Laboratoire de Cristallochimie
Institut de Chimie des Substances Naturelles, CNRS
F-91198 Gif-sur-Yvette (France)
Dr. J. P. Sauvage, Dr. C. 0. Dietrich-Buchecker
Laboratoire de Chimie Organo-Minerale, UA 422 du CNRS
Institut de Chimie, Universite Louis Pasteur
F-67008 Strasbourg (France).
I**] This work was supported by the Centre National de la Recherche Scientifique (CNRS).
1154
fJ VCH Vedagsgesellschafl mbH. 0-6940 Weinheim, 1990
Fig. 1. Structural formula (top) and ORTEP of the knotted compound. For
sake of clarity, the written symbols corresponding to the crystallographic numbering have all been omitted, those of 0 partly omitted. A denotes CuA and B
denotes CUB.
The X-ray crystallographically determined molecular
structure is shown in Figure 1
The molecule has
effective D , symmetry, with three mutually perpendicular
pseudo-twofold axes, one joining the two copper cations,
one passing through the middle of the two (CH,), bridges,
and the third one passing through the central oxygens of the
two polyoxyethylene chains. The symmetry places the two
complexes around CuA and CUB,with their respective 1,lOphenanthroline rings (CuA with phen A and phen A and
CUBwith phen B and phen B ) in superimposed fashion: A
over B , and A over B. Starting from phen A, the molecular
0570-0833/90/10iO-l154J 3.50+.25/0
Angew. Chem. I n ! . Ed. €&
29 (1990) No.10
Документ
Категория
Без категории
Просмотров
0
Размер файла
478 Кб
Теги
benzocyclobutene, thermal, benzocyclobutadieno, hydrogenation, trish, cis, central, structure, synthesis, cyclohexatrien, cyclohexane, isomerization, faciles, benzenes, photochemical
1/--страниц
Пожаловаться на содержимое документа