Syntheses of donor-acceptor-substituted 2,6-stellanes

Article abstract of DOI:10.1002/(SICI)1099-0690(199901)1999:1<73::AID-EJOC73>3.0.CO;2-B

A number of condensations could be carried out using tricyclo[3.3.0.0^3,7]octane-2-one (stellanone, 4) and tricyclo[3.3.0.0^3,7]octane-2,6-dione (2,6-stelladione, 5) as starting materials. The components for condensations were 2-trimethylsilyl-1,3- dithlane (6), 1,1-bis(trimethylsilyl)-1H-cyclopropa[b]naphthalene (7), its 3,6-dimethoxy-substituted analogue 8, fluorene (12), xanthene (13), diethyl malonate (14), and malononitrile (15). The condensation reactions with 5 yielded mono- and disubstituted products, among them were the donor-acceptor- substituted 2,6-stellanes 33-35. The structures of 18 (prepared from stellanone and fluorene), 19, 24, 27, 31 and 32 (synthesized by condensation of 2,6-stelladione and 2-trimethylsilyl- 1,3-dithiane and malononitrile, respectively) were determined by X-ray crystallography.

Full text of DOI:10.1002/(SICI)1099-0690(199901)1999:1<73::AID-EJOC73>3.0.CO;2-B

FULL PAPER
Syntheses of Donor–Acceptor-Substituted 2,6-Stellanes
Gerd Fritzsche,[a] Rolf Gleiter,*[a] Hermann Irngartinger,[a] and Thomas Oeser[a]
Keywords: Donor–acceptor systems / Cage compounds / Stelladione
A number of condensations could be carried out using
tricyclo[3.3.0.03,7]octane-2-one (stellanone, 4) and tricyclo-
[3.3.0.03,7]octane-2,6-dione (2,6-stelladione, 5) as starting
materials. The components for condensations were 2-
trimethylsilyl-1,3-dithiane (6), 1,1-bis(trimethylsilyl)-1H-
cyclopropa[b]naphthalene (7), its 3,6-dimethoxy-substituted
analogue 8, fluorene (12), xanthene (13), diethyl malonate
(14), and malononitrile (15). The condensation reactions with
5 yielded mono- and disubstituted products, among them
were the donor–acceptor-substituted 2,6-stellanes 33–35. The
structures of 18 (prepared from stellanone and fluorene), 19,
24, 27, 31 and 32 (synthesized by condensation of 2,6-
stelladione
and
2-trimethylsilyl-1,3-dithiane
and
malononitrile, respectively) were determined by X-ray
crystallography.
In many model investigations concerning electron-trans-
fer processes donor and acceptor units were used that are
connected by a rigid σ scaffold. Usually, the distances and
orientations of the π systems have been varied.[1] In those
compounds where the two systems are separated by more
Results and Discussion
In the preparation of the desired substituted stellenes and
stelladienes we chose different condensation methodologies.
Starting compounds were either stellanone (4)[6] or stella-
dione (5).[2,7,8] Their syntheses have been described in the
literature.[6,8] Further components were 2-trimethylsilyl-1,3-
dithiane (6),[9] 1,1-bis(trimethylsilyl)-1H-cyclopropa[b]-
naphthalene (7)[10] and its 3,6-dimethoxy-substituted prod-
uct 8. Starting from 3,6-dimethoxycyclopropa[b]naph-
thalene[11] we prepared 8 as a new coupling component.
˚
than 3 A the through-bond coupling should dominate;
therefore the nature of the σ system should be important.
In order to test this we have started a program in which
one varies not only the distance between the two π systems,
but also increases the bridging of the central σ system.[2,3]
If the bridges are small the angle strain within the scaffold
is intensified, which usually leads to an increase of the p
character of the CϪC bonds. A series of simple test systems
are 1Ϫ3.
In all three systems a central six-membered ring adopts
a boat or twist-boat conformation and the angle strain in-
creases from 1 to 3. Investigations by PE spectroscopy of
1Ϫ3 have shown that the energy difference between the π
ionization energies increases from 0.2 eV (1)[4] to 0.9 eV
(3).[5] A key system for our further investigations is a p-
stelladiene (3) unit bearing donor and acceptor units. In
this paper we describe our experimental efforts to join do-
nor and/or acceptor groups to the stellane skeleton.
Scheme 1. a: nBuLi/THF, Ϫ78°C; b: tBuOK/THF, Ϫ70°C
A convenient method for the olefination of 4 with elec-
tron-rich systems proved to be the Peterson reaction[12]
(Scheme 1). The reaction of 4 with 6Ϫ8 in the presence
of a strong base yielded 9Ϫ11, respectively, in medium to
good yields.
In the case of systems with acidic hydrogen atoms a
strong base was sufficient for the condensation (Scheme 2).
Treatment of fluorene (12) or xanthene (13) with LDA in
[a]
Organisch-Chemisches Institut der Universität Heidelberg,
Im Neuenheimer Feld 270, D-69120 Heidelberg, Germany
Eur. J. Org. Chem. 1999, 73Ϫ81
WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1999
1434Ϫ193X/99/0101Ϫ0073 $ 17.50ϩ.50/0
73

G. Fritzsche, R. Gleiter, H. Irngartinger, T. Oeser
FULL PAPER
reaction of 4 with diethyl malonate (14) in the presence of
TiCl4/pyridine afforded 20 in 48% yield. In order to obtain
the condensation product with malononitrile (15) the mix-
ture with 4 was refluxed in toluene in the presence of am-
monium acetate/acetic acid buffer. The yield of 21 was
only 2%.
Our experience with stellanone could be used to treat
stelladione (5) with fluorene (12) and xanthene (13)
(Scheme 4). Treatment of 12 and 13 with freshly prepared
LDA in the presence of 5 yielded the alcohols 22 and 24,
respectively. Dehydration afforded the ketones 23 and 25 in
reasonable yields. The reaction of 5 with 7 afforded 26 in
62% yield. The reaction of 5 with 6, 14 and 15 (Scheme 5)
afforded the anticipated monosubstituted products 27, 29,
and 31, as well as the disubstituted products 28, 30, and 32
as minor components.
Scheme 2. a: LDA/THF, Ϫ78°C; b: LDA/Me3SiCl/THF, 0°C;
c: pyridine POCl3, room temp.
Scheme 4. a: LDA/THF, Ϫ78°C; b: LDA/Me3SiCl/THF, 0°C. Ϫ
C: pyridine /POCl3, room temp.
Scheme 3. a: TiCl4/pyridine, 0°C; b: NH4OAc/HOAc/toluene,
reflux
The formation of 32 can be rationalized by assuming a
THF at Ϫ78°C led to the corresponding addition products rupture of one of the central CϪC bonds of the tricy-
16 and 17 in good yields. Further reaction of 16 with LDA clo[3.3.0.03,7]octane skeleton. The lengths of these bonds
˚
and trimethylsilyl chloride (TMSCl) yielded 18 almost (ca. 1.6 A, see below) make them succeptible to breaking.
quantitatively. In the case of 17 the same procedure yielded The structural assignment of 32 is based on its spectro-
the corresponding silyl ether, which proved to be rather scopic properties and on X-ray investigations of single crys-
stable towards strong bases. Finally, the reaction of 17 with tals. The donorϪacceptor-substituted stelladienes 33Ϫ35
POCl3 in the presence of pyridine led to 19 in 34% yield.
(Scheme 6) could be prepared from 23 and 25 by reaction
For the introduction of acceptor groups the Knoevenagel with 6 and 14, in an analogous way to the experiments sum-
condensation proved to be very helpful (Scheme 3). The marized in Schemes 1Ϫ5.
74
Eur. J. Org. Chem. 1999, 73Ϫ81

Syntheses of Donor–Acceptor-Substituted 2,6-Stellanes
FULL PAPER
Scheme 6. a: nBuLi/THF, Ϫ78°C; b: TiCl4/pyridine, 0°C
(Table 1) at the bridging bonds, which indicates nearly
eclipsed positions along these bonds. This gives rise to steric
strain that leads, in conjunction with the strain inherent in
the tricyclo[3.3.0.03,7]octane system, to the long bridging
˚
˚
bonds in the range of 1.594(3) A to 1.606(3) A (Table 1).
Furthermore, the CϪCϪC angles at the CH2 atoms are
considerably smaller [93.1(2)°Ϫ94.2(2)°] than the expected
angle for an sp3-carbon atom. The same effect is found for
the angles eϪf/kϪi [96.8(1)Ϫ98.2(2)°], which deviate con-
siderably from the anticipated 120°. This trend is in accord-
ance with our previous investigations on stellane com-
pounds.[2b,8,13] In the crystals of 19 and 32 there are two
independent molecules in the asymmetric unit. Further
structural details are in deposition.
Scheme 5. a: tBuOK/THF, Ϫ70°C; b: nBuLi/THF, Ϫ78°C;
c: TiCl4/pyridine, 0°C; d: NH4OAc/toluene, reflux
Structural Investigations
In the cases of 18, 19, 24, 27, 31, and 32 single crystals
suitable for X-ray analysis could be grown, which allowed
more detailed studies of the structural parameters of these
species. In Figure 1 the molecular structures of the three
stellane and stellanone derivatives 18, 27, and 31 are shown,
representing species with donor, acceptorϪdonor and ac-
ceptorϪacceptor capabilities. On average the single bonds
at the carbonyl groups of 24, 27, and 31 are shorter
Experimental Section
General Procedures: Reactions were carried out in oven-dried
(120°C) glassware under argon and with magnetic stirring. Solvents
were dried and distilled under argon before use. Ϫ1H and 13C
NMR: Bruker AS 200 and Bruker WH 300. If not otherwise noted
the 1H-NMR spectra were recorded at 300 MHz and the 13C-NMR
spectra at 75.47 MHz. Ϫ Low-resolution mass spectra were re-
corded with a Hewlett-Packard HP 59970 CD GC/MS-MSD. Ϫ
High-resolution mass spectra (HRMS) were obtained with a ZAB
˚
[1.523(3) A; averaged from Table 1) than the corresponding
˚
bonds of 18 and 19 [1.540(3) A].
The donor-substituted compounds of 18, 19, and 27 have
˚
bond lengths e and f of 1.514(3) A, while a shortening to
˚
1.498(2) A was noticed in compound 31, which is substi-
tuted by nitrile groups.
In five structures with the stellane framework we notice
only small torsional angles in the range of 0.1(2)° to 5.9(2)° high-resolution mass spectrometer (Vacuum Generators). Ϫ Mic-
Eur. J. Org. Chem. 1999, 73Ϫ81 75

G. Fritzsche, R. Gleiter, H. Irngartinger, T. Oeser
FULL PAPER
3,6-Dimethoxy-1,1-bis(trimethylsilyl)-1H-cyclopropa[b]naphthalene
(8): 2.1 mL (3.4 mmol) of a 1.6  solution of nBuLi in n-hexane
was slowly added at Ϫ78°C to a magnetically stirred solution of
534 mg (2.7 mmol) of 3,6-dimethoxycyclopropa[b]naphthalene[11]
in 15 mL of THF. The mixture was allowed to warm up to Ϫ50°C
during 1.5 h, maintained at that temperature for 0.5 h, and then
cooled to Ϫ78°C. Chlorotrimethylsilane (0.42 mL) was added
slowly and the mixture was allowed to warm to Ϫ40°C before be-
ing cooled to Ϫ70°C. The metallation and silylation procedure was
repeated twice, the first time with 1.4 mmol of 1.6  n-butyllithium
and 0.18 mL of chlorotrimethylsilane and the second time with 0.7
mmol of 1.6  n-butyllithium and 0.08 mL of chlorotrimethylsilane.
After the final silylation, the reaction mixture was allowed to warm
up to room temp. (2 h), before 5% aqueous NaHCO3 was added.
The mixture was extracted with pentane (ϫ 2) and the combined
organic layers were washed with water (ϫ 3) and dried (MgSO4).
Evaporation of the solvent and purification on silica gel gave 743
mg (82%) of 8 as air-sensitive colorless crystals, m.p. 143°C. Ϫ Rf
(silica gel, pentane/diethyl ether, 9:1) ϭ 0.62. Ϫ 1H NMR (CDCl3):
δ ϭ 7.49 (2 H, s), 6.67 (2 H, s), 3.93 (6 H, s), Ϫ0.03 (18 H, s). Ϫ
13C NMR (CDCl3): δ ϭ 149.8 (2 C, s), 131.2 (2 C, s), 127.3 (2 C,
s), 103.2 (2 C, d), 102.0 (2 C, d), 55.6 (2 C, q), 28.8 (s), Ϫ1.5 (6 C,
q). Ϫ UV/Vis (CH2Cl2): λmax (log ε) ϭ 224 nm (4.52), 270 (4.60),
294 (3.93), 308 (3.88), 330 (3.60). Ϫ IR (KBr): ν˜ ϭ 3066 cmϪ1 (w),
3005 (w), 2952 (s), 2901 (m), 2831 (m), 1785 (w), 1611 (m), 1581
(w), 1464 (s), 1436 (m), 1363 (w), 1303 (s), 1258 (vs). Ϫ MS (70
eV); m/z (%): 344 (34) [M•ϩ] 331 (10), 330 (27), 329 (100). Ϫ
C19H28O2Si2 (344.60): calcd. C 66.25, H 8.20; found C 65.98, H
8.17.
2-(1,3-Dithian-2-ylidene)tricyclo[3.3.0.03,7]octane (9): 1.2 mL (2.0
mmol) of a 1.6  solution of nBuLi in n-hexane was added at
Ϫ78°C to a magnetically stirred solution of 385 mg (2.0 mmol) of
2-trimethylsilyl-1,3-dithiane (6) in 50 mL of THF. The solution was
allowed to warm up to 0°C. After cooling to Ϫ78°C, 244 mg (2.0
mmol) of 4, dissolved in 10 mL of THF, was added and the reaction
mixture was maintained at Ϫ78°C for 1 h and subsequently
warmed to 0°C. The mixture was hydrolyzed with water, the solvent
evaporated and the residue directly chromatographed on silica gel
with pentane/diethyl ether (9:1) to yield 403 mg (90%) of 9 as a
pale yellow solid, m.p. 39°C: Ϫ Rf (silica gel, pentane) ϭ 0.28; Rf
(silica gel, pentane/diethyl ether, 9:1) ϭ 0.85. Ϫ 1H NMR (CDCl3):
δ ϭ 2.95Ϫ2.92 (2 H, m), 2.82Ϫ2.72 (4 H, m), 2.41 (2 H, s, br),
2.16Ϫ2.11 (2 H, m), 1.57Ϫ1.25 (6 H, m). Ϫ 13C NMR (CDCl3):
δ ϭ 163.4 (s), 99.2 (s), 44.6 (2 C, t), 44.2 (t), 40.8 (2 C, d), 36.9 (2
C, d), 30.9 (2 C, t), 26.2 (t). Ϫ UV/Vis (CH2Cl2): λmax (log ε) ϭ
224 nm (3.96), 256 (4.01). Ϫ IR (KBr): ν˜ ϭ 3440 cmϪ1 (s, br.),
2952 (vs), 2926 (vs), 2880 (s), 2821 (w), 1637 (m). Ϫ MS (70 EV);
m/z (%): 224 [M•ϩ] (100), 196 (13), 183 (68). Ϫ C12H16S2 (224.38):
calcd. C 64.24, H 7.19; found C 64.40, H 7.41.
Figure 1. Molecular structures of 18 (top), 27 (middle) and 31 (bot-
tom);[16] selected bond lengths [A] and angles [°]: 18: C1ϪC2 1.546
˚
(3), C2ϪC3 1.527 (3), C2ϪC7 1.597 (3), C3ϪC4 1.552 (3), C4ϪC5
1.606 (3), C8ϪC9 1.351 (2), C9ϪC10 1.487 (2), C10ϪC11 1.388
(3), C10ϪC15 1.411 (2); C5ϪC1ϪC2 93.3 (2), C3ϪC2ϪC1 97.6
(2), C3ϪC2ϪC7 102.0 (2), C2ϪC3ϪC4 93.8 (2), C4ϪC8ϪC7 95.5
(1); 27: O1ϪC1 1.204(3), C1ϪC2 1.531(3), C2ϪC3 1.549(3),
C3ϪC4 1.556(3), C4ϪC5 1.513(3), C5ϪC6 1.507(2), C6ϪC7
1.554(3), C7ϪC8 1.548(3), C2ϪC6 1.592(3), C4ϪC8 1.595(3),
C5ϪC9 1.334(3), C9ϪS1 1.768(2), C9ϪS2 1.769(2); O1ϪC1ϪC2
131.4(2), C2ϪC1ϪC8 97.3(2), C1ϪC2ϪC3 93.8(2), C2ϪC3ϪC4
94.1(2), C3ϪC4ϪC5 95.7(2), C4ϪC5ϪC6 96.8(2), C1ϪC2ϪC6
101.0(2), C1ϪC8ϪC4 102.0(2), C4ϪC5ϪC9 131.8(2); 31: O1ϪC2
1.204 (3), C1ϪC2 1.523 (2), C1ϪC3Ј 1.552 (2), C1ϪC4 1.594 (2),
C3ϪC4 1.554 (2), C4ϪC5 1.498 (2), C5ϪC6 1.335(3), N1ϪC7
1.144 (2), C6ϪC7 1.437 (2); C1ϪC2ϪC1Ј 97.3 (2), C1ϪC4ϪC3
103.0 (1), C3ϪC4ϪC5 95.0 (2), C1ϪC3ϪC4 94.1 (1), C4ϪC5ϪC4Ј
98.2 (2), C7ϪC6ϪC7Ј 119.4 (2), N1ϪC7ϪC6 176.5 (2)
2-(1H-Cyclopropa[b]naphthalen-1-ylidene)tricyclo[3.3.0.03,7]octane
(10): Potassium tert-butoxide (217 mg (1.9 mmol) in 7 mL of THF
was slowly added at Ϫ70°C to a magnetically stirred solution of
427 mg (1.5 mmol) of 7 in 25 mL of THF. The reaction temp. was
raised to Ϫ30°C, maintained there for 0.5 h, and then lowered to
Ϫ70°C. The anion was quenched at Ϫ70°C with 220 mg (1.8
mmol) of ketone 4, dissolved in 10 mL of THF, and the reaction
mixture warmed to room temp. during 1.5 h. THF was evaporated
under reduced pressure. After addition of 5% aqueous NH4Cl, the
residue was extracted with diethyl ether (ϫ 3) and the combined
organic layers were washed with water and dried (MgSO4). After
evaporation of the solvent, purification on silica gel (pentane) gave
218 mg (60%) of 10 as a pale yellow solid, m.p. 122°C. Ϫ Rf (silica
gel, pentane) ϭ 0.52. Ϫ 1H NMR (CD2Cl2): δ ϭ 7.79 (2 H, dd,
roanalyses: Analytical laboratory of the Chemische Institute der
Universität Heidelberg.
76
Eur. J. Org. Chem. 1999, 73Ϫ81

Syntheses of Donor–Acceptor-Substituted 2,6-Stellanes
FULL PAPER
Table 1. Selected geometrical parameters of 18, 19, 24, 27, and 31 (geometrical parameters of 19 are averaged values of both inde-
pendent molecules)
18
19
24
27
31
˚
Bond length [A]
a
1.597(3)
1.606(3)
1.511(2)
1.516(2)
1.534(3)
1.546(3)
1.604(3)
1.616(3)
1.517(3)
1.519(2)
1.541(3)
1.537(3)
1.602(3)
1.594(3)
1.556(2)
1.543(2)
1.526(3)
1.522(3)
1.592(3)
1.595(3)
1.513(3)
1.507(2)
1.514(3)
1.531(3)
1.594(2)
Ϫ
1.498(2)
Ϫ
1.523(2)
Ϫ
b
e
f
i
k
Bond angle [°]
c؊d
93.8(2)
93.7(2)
95.5(1)
93.3(2)
93.8(2)
93.4(2)
95.5(2)
93.1(2)
93.8(2)
93.8(2)
92.6(1)
96.8(1)
94.1(2)
94.2(2)
96.8(2)
97.3(2)
Ϫ
g؊h
94.1(1)
98.2(2)
97.3(2)
e؊f
k؊i
Torsion angle
c؊a؊f
k؊a؊g
d؊b؊i
e؊b؊h
2.6(2)
0.6(2)
1.8(2)
1.4(2)
1.4(2)
1.4(2)
1.4(2)
2.0(2)
5.9(2)
4.8(2)
4.0(2)
3.4(2)
0.4(2)
1.8(2)
2.4(2)
0.1(2)
0.5(1)
1.6(1)
Ϫ
Ϫ
J ϭ 6.1, J ϭ 3.4 Hz), 7.41 (2 H, dd, J ϭ 6.2, J ϭ 3.3 Hz), 7.24 (2 during 2 h and then hydrolyzed with water and the solvent evapo-
H, s), 3.08Ϫ3.06 (2 H, m), 2.56 (2 H, s, br.), 1.67Ϫ1.58 (6 H, m).
13C NMR (CD2Cl2): δ ϭ 141.2 (s), 137.9 (2 C, s), 128.6 (2 C,
d), 127.8 (2 C, s), 126.1 (2 C, d), 105.6 (2 C, d), 93.6 (s), 46.3 (2 C,
rated under reduced pressure. Water and CH2Cl2 were added. The
separated aqueous layer was extracted twice with CH2Cl2 and the
combined organic layers were washed with NH4Cl and brine and
concentrated. Purification of the residue by silica gel chromatogra-
Ϫ
t), 44.9 (t), 42.5 (2 C, d), 37.7 (2 C, d). Ϫ UV/Vis (CH2Cl2): λmax
(log ε) ϭ 234 nm (4.55), 264 (4.31) 276 (4.49), 354 (4.40), 364 phy (pentane/ethyl acetate, 20:1) gave 1.05 g (91%) of 16 as a color-
(4.36), 374 (4.64). Ϫ IR (KBr): ν˜ ϭ 3049 cmϪ1 (m), 2998 (vs), 2869
(s), 1577 (s), 1518 (s), 1433 (s). Ϫ MS (70 eV); m/z (%): 244 [M•ϩ
(69), 243 (13), 229 (25), 228 (36), 217 (11), 216 (41), 215 (93), 204
less solid, m.p. 130°C. Ϫ Rf (silica gel, pentane/diethyl ether, 9:1) ϭ
0.20. Ϫ H NMR (CDCl3): δ ϭ 7.78Ϫ7.75 (2 H, m), 7.70Ϫ7.64 (2
H, m), 7.42Ϫ7.25 (4 H, m), 4.53 (1 H, s, br), 2.73 (1 H, m), 2.61
1
]
(18), 203 (100), 202 (96). Ϫ HRMS: calcd. for C19H16 244.1252; (1 H, s, br.), 2.54Ϫ2.50 (1 H, m), 2.41 (1 H, d, J ϭ 2.5 Hz), 2.32
found 244.1256.
(1 H, s, br.), 1.69Ϫ1.66 (1 H, m), 1.58Ϫ1.55 (2 H, m), 1.44 (1 H,
m, br.), 1.28Ϫ1.23 (1 H, m), 1.01 (1 H, m). Ϫ 13C NMR (CDCl3):
δ ϭ 144.5 (s), 144.4 (s), 142.6 (s), 141.9 (s), 127.7 (d), 127.5 (d),
127.0 (d), 126.9 (d), 125.4 (d), 125.3 (d), 120.1 (d), 119.9 (d), 89.2
(COH), 52.9 (CHCp), 47.4 (t), 45.2 (d), 43.7 (d), 40.0 (t), 39.8 (t),
38.7 (d), 37.8 (d). Ϫ UV/Vis (CH2Cl2): λmax (log ε) ϭ 226 nm (3.9),
168 (4.24), 292 (3.73), 302 (3.8) nm. Ϫ IR (KBr): ν˜ ϭ 3520 cmϪ1
(w), 3396 (w, br.), 3016 (m), 2980 (m), 2937 (w), 2895 (w), 1448 (s).
Ϫ MS (70 eV); m/z (%): 289 (1), 288 [M•ϩ] (1), 167 (12), 166 (90),
165 (100). Ϫ C21H20O (288.39): calcd. C 87.46, H 6.99; found C
87.46, H 7.01.
2-(3,6-Dimethoxy-1H -cyclopropa[b]naphthalen-1-ylidene)tri-
cyclo[3.3.0.03,7]octane (11): The preparation of 11 was carried out
analogously to the preparation of 10. Starting materials: 345 mg
(1.0 mmol) of 8, 141 mg (1.3 mmol) of potassium tert-butoxide,
159 mg (1.3 mmol) of 4. The reaction yielded 129 mg (42%) of 11
as a yellow solid, 122°C. Ϫ Rf (silica gel, pentane/CH2Cl2, 1:1) ϭ
1
0.77. Ϫ H NMR (CD2Cl2): δ ϭ 7.65 (2 H, s), 6.76 (2 H, s), 3.97
3
3
(6 H, s), 3.09 (2 H, dd, J ϭ 4.7, J ϭ 2.5 Hz), 2.58 (2 H, s, br.),
1.68 (2 H, m), 1.60Ϫ1.56 (4 H, m, br.). Ϫ 13C NMR (CD2Cl2): δ ϭ
150.8 (2 C, CϪO), 139.8 (s), 129.8 (2 C, s), 127.7 (2 C, s), 104.4 (2
C, d), 100.3 (2 C, d), 93.6 (s), 56.2 (2 C, q), 46.4 (2 C, t), 44.9 (t),
42.4 (2 C, d), 37.6 (2 C, d). Ϫ UV/Vis (CH2Cl2): λmax (log ε) ϭ
224 nm (4.45), 292 (4.58), 300 (4.65), 342 (4.13), 354 (4.32), 374
(4.47). Ϫ IR (KBr): ν˜ ϭ 2957 cmϪ1 (s), 1613 (s), 1465 (s), 1437 (w).
Ϫ MS (70 eV); m/z (%): 304 (19), 269 (10), 263 (17), 233 (16), 201
(13), 200 (88), 186 (14), 185 (100). Ϫ HRMS: calcd. for C21H20O2
304.1463; found 304.1451.
2-(9H-Xanthen-9-yl)tricyclo[3.3.0.03,7]octane-2-ol (17): The prep-
aration of 17 was accomplished in an analogous way to 16. Starting
materials: 916 mg (7.5 mmol) of 4, 2.4 g (13.0 mmol) of 13. The
reaction yielded 2.2 g (96%) of 17 as a colorless solid, m.p. 200°C.
Ϫ Rf (silica gel, pentane/diethyl ether, 9:1) ϭ 0.25. Ϫ 1H NMR
([D6]DMSO) δ ϭ 7.37Ϫ7.01 (8 H, m), 4.57 (1 H, s), 4.43 (1 H, s),
2.64Ϫ2.60 (1 H, m), 2.44 (1 H, s, br.), 2.17 (2 H, s, br.), 2.06 (1 H,
s, br.), 1.63 (1 H, s), 1.43 (2 H, m), 1.24 (1 H, d, J ϭ 8.7 Hz), 0.96
(1 H, m). Ϫ 13C NMR ([D6]DMSO) δ ϭ 153.7 (s), 153.0 (s), 130.3
(d), 127.7 (d), 127.2 (d), 127.1 (d), 123.7 (s), 123.5 (s), 122.2 (t),
122.0 (d), 115.9 (d), 115.6 (d), 90.7 (s), 46.6 (t), 43.2 (d), 42.9 (d),
40.8 (d), 39.8 (t), 39.6 (t), 38.2 (d), 36.9 (d). Ϫ UV/Vis (CH2Cl2):
λmax (log ε) ϭ 222 nm (3.92), 246 (3.98), 286 (3.51). Ϫ IR (KBr):
ν˜ ϭ 3562 cmϪ1 (m), 3486 (s), 3025 (m), 2986 (vs), 2940 ( m), 2918
(m), 2901 (m), 1597 (m), 1574 (m), 1479 (vs), 1454 (vs), 1250 (vs).
2-(Fluoren-9-yl)tricyclo[3.3.0.03,7]octane-2-ol (16): To a magnetically
stirred solution of lithium diisopropylamide Ϫ prepared at 0°C
from 1.1 mL (8.0 mmol) of diisopropylamine and 5 mL (8 mmol)
of 1.6  n-butyllithium in n-hexane in 60 mL of THF, was added
1.2 g (8.0 mmol) of fluorene (12), dissolved in 170 mL of THF, at
Ϫ78°C. The solution was stirred for 15 min and then added drop-
wise at Ϫ78°C to 489 mg (4.0 mmol) of ketone 4, dissolved in 170
mL of THF. The solution was allowed to warm up to room temp.
Eur. J. Org. Chem. 1999, 73Ϫ81
77

G. Fritzsche, R. Gleiter, H. Irngartinger, T. Oeser
Ϫ MS (70 eV); m/z (%): 304 [1M•ϩ], 183 (8), 182 (60), 181 (100). Ϫ 1.31 (6 H, t, J ϭ 7.1 Hz). Ϫ 13C NMR (CD2Cl2): δ ϭ 177.8 (s),
FULL PAPER
3
C21H20O2 (304.39): calcd. C 82.87, H 6.62; found C 82.66, H 6.58.
165.6 (2 C, CϭO), 108.2 (s), 61.0 (2 C, CH2ϪOϪ), 44.6 (t), 43.8
(2 C, t), 41.6 (2 C, d), 37.2 (2 C, d), 14.4 (2 C, q). Ϫ UV/Vis
(CH2Cl2): λmax (log ε) ϭ 226 nm (4.39), 246 (4.03), 260 (3.81), 314
(3.92). Ϫ IR (KBr): ν˜ ϭ 2980 cmϪ1 (s), 2883 (w), 1719 (vs), 1662
(m), 1466 (w). Ϫ MS (70 eV); m/z (%): 264 [M•ϩ] (7), 219 (68), 218
(48), 199 (11), 198 (98), 190 (36), 177 (32), 173 (23), 172 (100), 170
(55). Ϫ HRMS: calcd. for C15H20O4 264.1225; found 264.1293.
2-(Fluoren-9-ylidene)tricyclo[3.3.0.03,7]octane (18): A solution of
300 mg (1.0 mmol) of 16 in 10 mL of THF was added to a magneti-
cally stirred solution of lithium diisopropylamide Ϫ prepared at
0°C from 0.3 mL (2.0 mmol) of diisopropylamine and 1.3 mL (2.0
mmol) of 1.6  n-butyllithium in n-hexane in 60 mL of THF. The
reaction mixture was stirred at 0°C for 30 min, then 0.6 mL (5.0
mmol) of chlorotrimethylsilane was added dropwise and the mix-
(Tricyclo[3.3.0.03,7]octan-2-ylidene)propanedinitrile (21): A mixture
ture was allowed to warm up to room temp. The reaction mixture of 2.0 g (16.4 mmol) of 4, 5.3 g (80.0 mmol) of malononitrile, 5.3
was hydrolyzed with water and extracted with diethyl ether (ϫ 3).
The combined organic layers were washed with 5% aqueous
NaHCO3, water, brine and the solvent was evaporated. Purification
of the residue by silica gel chromatography (elution with pentane/
diethyl ether, 20:1) gave 257mg of 18 (95%) as colorless crystals,
g (69.0 mmol) of ammonium acetate, and 15.8 mL of acetic acid
in 120 mL of toluene was refluxed for 42 h in a DeanϪStark appa-
ratus. After addition of 5% aqueous NaHCO3, the phases were
separated. Extraction was effected twice with toluene and the com-
bined organic layers were washed with water and dried with MgSO4
m.p. 182°C. Ϫ Rf (silica gel, pentane/diethyl ether, 20:1) ϭ 0.68. Ϫ and the solvent was evaporated. Purification by silica gel chroma-
1H NMR (CDCl3): δ ϭ 7.98Ϫ7.93 (2 H, m), 7.82Ϫ7.77 (2 H, m),
tography (elution with pentane/diethyl ether, 4:1) gave 65 mg of 21
7.36Ϫ7.28 (4 H, m), 3.81 (2 H, s), 2.63 (2 H, s), 1.67 (6 H, s). Ϫ (2.3%) as a colorless solid. Ϫ Rf (silica gel, pentane/diethyl ether,
1
3
13C NMR (CDCl3): δ ϭ 162.8 (s), 139.4 (2 C, s), 139.3 (2 C, s),
126.6 (2 C, d), 126.2 (2 C, d), 123.1 (2 C, d), 119.5 (2 C, d), 115.9
4:1) ϭ 0.27. Ϫ H NMR (CD2Cl2): δ ϭ 3.09 (2 H, dd, J1 ϭ 5.2,
3J2 ϭ 2.6 Hz), 2.64 (2 H, m, br.), 1.73Ϫ1.54 (6 H, m). Ϫ 13C NMR
(s), 44.6 (t), 44.0 (2 C, t), 40.3 (2 C, d), 37.5 (2 C, d). Ϫ UV/Vis (CD2Cl2): δ ϭ 186.5 (C), 112.1 (2 C, CN), 100.0 (C), 44.1 (2 C, d),
(CH2Cl2): λmax (log ε) ϭ 236 nm (4.58), 258 (4.14), 282 (4.17), 292
(4.21), 306 (4.02), 320 (4.06). Ϫ IR (KBr): ν˜ ϭ 3440 cmϪ1 (s, br.),
44.0 (t), 43.9 (2 C, t), 38.1 (2 C, d). Ϫ UV/Vis (CH2Cl2): λmax (log
ε) ϭ 240 nm (4.17). Ϫ IR (KBr): ν˜ ϭ 3012 cmϪ1 (m), 2960 (m),
3048 (w), 2977 (s), 2957 (s), 2878 (w), 1654 (vs), 1445 (vs). Ϫ MS 2882 (m), 2234 (s), 1634 (vs), 1301 (w), 1142 (w), 1083 (w). Ϫ MS
(70 eV); m/z (%): 270 [M•ϩ] (100), 243 (12), 242 (48), 241 (33), 229 (70 eV); m/z (%): 170 [M•ϩ] (26), 169 (24), 155 (21), 143 (19), 142
(51), 228 (28), 226 (11). Ϫ C21H18 (270.37): calcd. C 93.29, H 6.71; (76), 129 (27), 128 (29), 115 (23), 105 (12). Ϫ HRMS: calcd. for
found C 93.03, H 6.88.
C11H10N2 170.0844; found 170.0825.
2-(9H-Xanthen-9-ylidene)tricyclo[3.3.0.03,7]octane (19): 0.8 mL of
(Fluoren-9-yl)-6-hydroxytricyclo[3.3.0.03,7]octane-2-one (22): The
POCl3 (8.7 mmol) was added at 0°C to a solution of 609 mg (2.0 preparation of 22 was accomplished in an analogous way to that
mmol) of 17 in 10.2 mL of pyridine. The brown mixture was stirred
for 90 h at room temp. and was then poured into a mixture of
ice/water and ethyl acetate. After extraction, the organic layer was
of 16. Starting materials: Lithium salt of fluorene, prepared from
1.3 g (8.0 mmol) of 12 and 544 mg (4.0 mmol) of 5. The reaction
yielded 572 mg (47%) of 22 as a colorless solid. Ϫ Rf (silica gel,
washed with 5% aqueous NaHCO3 and with brine. The residue was pentane/diethyl ether, 1:1) ϭ 0.17. Ϫ 1H NMR (CDCl3): δ ϭ
chromatographed on silica gel (elution with benzene) to yield 194
7.81Ϫ7.28 (8 H, m), 4.40 (1 H, s), 2.97 (1 H, br., m), 2.71 (1 H,
dd, J ϭ 11.7, J ϭ 3.0 Hz), 2.64Ϫ2.60 (3 H, m), 2.42 (1 H, br., m),
1.65Ϫ1.61 (1 H, m), 1.49 (1 H, dd, J ϭ 11.8, J ϭ 2.1 Hz),
1.37Ϫ1.22 (1 H, m). Ϫ 13C NMR (CDCl3): δ ϭ 208.9 (s), 143.3
(s), 142.9 (s), 142.6 (s), 141.9 (s), 128.2 (d), 127.9 (d), 127.3 (2 C,
mg of 19 (34%) as colorless crystals, 197°C. Ϫ Rf (silica gel, ben-
1
zene) ϭ 0.80. Ϫ H NMR (CD2Cl2): δ ϭ 7.51Ϫ7.12 (8 H, m), 3.32
(2 H, s, br.), 2.54 (2 H, s, br.), 1.58 (6 H, s, br.). Ϫ 13C NMR
(CD2Cl2): δ ϭ 154.9 (s), 152.4 (2 C, s), 125.8 (2 C, d), 125.6 (2 C,
d), 124.8 (2 C, s), 121.8 (2 C, d), 114.9 (2 C, d), 105.3 (s), 43.4 (2 d), 125.4 (d), 125.1 (d), 120.3 (d), 120.2 (d), 87.1 (s), 52.6 (d), 46.0
C, t), 43.2 (t), 38.7 (2 C, d), 35.9 (2 C, d). Ϫ UV/Vis (CH2Cl2): (d), 45.8 (d), 44.5 (d), 41.7 (d), 34.2 (t), 33.5 (t). Ϫ UV/Vis
λmax (log ε) ϭ 230 nm (3.85), 244 (3.90), 284 (3.45), 314 (3.23). Ϫ
IR (KBr): ν˜ ϭ 3074 cmϪ1 (w), 3025 (m), 2966 (s), 2880 (w), 1656 (3.64), 342 (316). Ϫ IR (KBr): ν˜ ϭ 3426 cmϪ1 (s, br.), 3014 (w),
(w), 1590 (w), 1469 (m), 1445 (s), 1254 (vs), 1200 (s). Ϫ MS (70
1768 (vs). Ϫ MS (70 eV); m/z (%): 303 (10), 302 [M•ϩ] (44), 222
eV); m/z (%): 286 [M•ϩ] (100), 285 (30), 267 (11), 258 (18), 257 (8), 167 (17), 166 (100), 165 (91). Ϫ C21H18O2 (302.37): calcd. C
(CH2Cl2): λmax (log ε) ϭ 220 nm (4.21), 268 (4.2), 292 (3.59), 302
(35), 246 (15), 245 (74), 244 (10), 243 (12), 231 (13). Ϫ C21H18
O
83.42, H 6.00; found C 83.25, H 5.92.
(286.37): calcd. C 88.08, H 6.33; found C 88.16, H 6.32.
6-(Fluoren-9-ylidene)tricyclo[3.3.0.03,7]octane-2-one (23): The prep-
aration of 23 was carried out as described for 18. Starting materi-
als: 216 mg (0.7 mmol) of 22 and 0.45 mL (3.6 mmol) of chlorotri-
Diethyl 2-(Tricyclo[3.3.0.03,7]octan-2-ylidene)propanedioate (20): 0.9
mL of TiCl4 (9.0 mmol) was added at 0°C to a mixture of 2.0 mL
of CCl4 and 4.0 mL of THF. A solution of 0.6 mL (4.0 mmol) of methylsilane. This reaction yielded 173 mg (85%) of 23. Alterna-
diethyl malonate and 489 mg (4.0 mmol) of 4 in 3 mL of THF was tively, 23 was prepared in a one-pot reaction: To a magnetically
added to the cooled precipitate. This addition was followed by a
solution of 1.3 mL (16.0 mmol) of pyridine in 9.0 mL of THF. The from 6.75 mL (48.0 mmol) of diisopropylamine and 4.8 mL (48.0
reaction mixture was allowed to warm up to room temp and stirred mmol) of 10  n-butyllithium in n-hexane in 150 mL of THF was
for 3 d before it was poured into ice-cold water. Extraction was added 4.0 g (24.0 mmol) of 5, dissolved in 100 mL of THF, at
stirred solution of lithium diisopropylamide Ϫ prepared at 0°C
effected with ethyl acetate (ϫ 3). The combined organic layers were
washed with 5% aqueous NH4Cl and with brine. The solvent from
the organic layer was evaporated and after purification of the resi-
Ϫ78°C. The solution was allowed to warm up to Ϫ40°C for 15
min and then cooled to Ϫ78°C again. The resulting solution was
added dropwise to 3.0 g (22.0 mmol) of 5, dissolved in 200 mL of
due by silica gel chromatography (pentane/ethyl acetate, 20:1) THF, at Ϫ78°C. The solution was allowed to warm up to Ϫ45°C
yielded 510 mg (48%) of 20 as a yellow solid, m.p. 30°C. Ϫ Rf for 1 h, recooled to Ϫ78°C, and chlorotrimethylsilane (15.2 mL,
(silica gel, pentane/ethyl acetate, 20:1) ϭ 0.24. Ϫ 1H NMR
(CD2Cl2): δ ϭ 4.22 (4 H, dq, J ϭ 7.1, J ϭ 1.6 Hz), 3.23 (2 H, dd,
3J ϭ 5.0, 3J ϭ 2.5 Hz), 2.50 (2 H, m, br.), 1.62Ϫ1.49 (6 H, m),
120.0 mmol) was added dropwise. After 30 min, the mixture was
allowed to warm to room temp. The reaction mixture was hy-
drolyzed with water and extracted with diethyl ether (ϫ 3). The
3
78
Eur. J. Org. Chem. 1999, 73Ϫ81

Syntheses of Donor–Acceptor-Substituted 2,6-Stellanes
FULL PAPER
3
2
3
combined organic layers were washed with 5% aqueous NaHCO3,
water, and with brine and then the solvent was evaporated. The
product was purified using flash column chromatography (pentane
H, d, J ϭ 0.9 Hz), 2.48 (2 H, dd, J ϭ 5.1, J ϭ 2.5 Hz), 1.91 (2
2
3
2
3
H, dd, J ϭ 11.3, J ϭ 1.4 Hz), 1.82 (2 H, dd, J ϭ 11.4, J ϭ 2.3
Hz). Ϫ 13C NMR (CDCl3): δ ϭ 211.8 (CϭO), 137.8 (2 C, s), 131.7
to remove fluorene and then pentane/diethyl ether, 1:1 to elute the (s), 128.6 (d), 126.3 (2 C, d), 125.8 (2 C, s), 107.1 (2 C, d), 98.5 (2
desired product). The reaction yielded 3.9 g (58%) of 23 as a color- C, s), 44.2 (2 C, d), 40.8 (2 C, d), 38.9 (2 C, t). Ϫ UV/Vis (CH2Cl2):
less solid, m.p. 159°C. Ϫ Rf (silica gel, pentane/diethyl ether, 1:1) ϭ λmax (log ε) ϭ 232 nm (4.6), 262 (3.34), 274 (4.50), 320 (3.82), 336
1
0.56. Ϫ H NMR (CD2Cl2): δ ϭ 7.93 (2 H, dd, J ϭ 6.7, J ϭ 1.6 (4.06), 350 (4.38), 362 (4.35), 372 (4.65). Ϫ IR (KBr): ν˜ ϭ 3439
Hz), 7.80 (2 H, dd, J ϭ 6.6, J ϭ 1.9 Hz), 7.40Ϫ7.30 (4 H, m), 4.10
(2 H, m), 2.50Ϫ2.49 (2 H, m), 1.93Ϫ1.81 (4 H, m). Ϫ 13C NMR
cmϪ1 (m, br.), 3017 (w), 2931 (w), 2865 (w), 1779 (vs), 1768 (vs),
1628 (w), 1607 (w), 1517 (w). Ϫ MS (70 eV): m/z ϭ 259 (3), 258
(CD2Cl2): δ ϭ 211.0 (s), 154.1, 139.7 (2 C, s), 138.2 (2 C, s), 127.1 [M•ϩ] (14), 202 (10), 179 (15), 178 (100). Ϫ HRMS: calcd. for
(2 C, d), 126.8 (d), 122.9 (2 C, d), 121.4 (2 C), 119.6 (2 C, d), 43.8
(2 C, d), 38.5 (2 C, d), 36.0 (2 C, t). Ϫ UV/Vis (CH2Cl2): λmax (log
ε) ϭ 234 nm (4.55), 248 (4.27), 258 (4.34), 278 (4.17), 286 (4.19),
302 (4.09), 314 (4.1). Ϫ IR (KBr): ν˜ ϭ 3041 cmϪ1 (w), 2935 (w),
2864 (w), 1768 (vs), 1668 (w), 1475 (s), 779 (m), 733 (s). Ϫ MS (70
eV); m/z (%): 285 (8), 284 [M•ϩ] (32), 256 (16), 155 (15), 241 (14),
239 (11), 229 (29), 228 (29), 227 (12), 226 (15), 215 (16), 202 (13),
202 (25), 191 (10), 190 (10), 189 (18), 178 (17), 166 (17), 165 (100).
Ϫ HRMS: calcd. for C21H16O 284.1201; found 284.1186.
C19H14O 258.1045; found 258.0998.
6-(1,3-Dithian-2-ylidene)tricyclo[3.3.0.03,7]octan-2-one (27) and 2,6-
Bis(1,3-dithian-2-ylidene)tricyclo[3.3.0.03,7]octane (28): The reaction
of 5 with 6 was carried out analogously to the reaction of 4 with
6. Starting materials: 544 mg (4.0 mmol) of 5 and 0.7 mL (4.0
mmol) of 6. This reaction yielded 807 mg (85%) of 27 and 29 mg
(2%) of 28 as colorless crystals. Separation was accomplished by
silica gel chromatography (pentane/diethyl ether, 9:1). Ϫ 27: M.p.
122°C. Ϫ Rf (silica gel, pentane/diethyl ether, 9:1) ϭ 0.21. Ϫ 1H
NMR (CDCl3): δ ϭ 3.23 (2 H, s, br.), 2.89Ϫ2.76 (4 H, m), 2.33 (2
6-Hydroxy-6-(xanthen-9-yl)tricyclo[3.3.0.03,7]octane-2-one (24): The
preparation of 24 was carried out as described for 17. Starting ma-
terials: lithium salt of 13, prepared from 5.8 g (32.0 mmol) of 13,
and 4 g (29.0 mmol) of 5. This reaction yielded 7.5 g (81%) of 24
as a colorless solid, m.p. 184°C. Ϫ Rf (silica gel, pentane/ether,
3
3
H, dd, J ϭ 5.1, J2 ϭ 2.5 Hz), 2.19Ϫ2.11 (2 H, m), 1.70 (2 H, d,
2J ϭ 11.4 Hz), 1.58 (2 H, dd, 2J ϭ 11.4, 3J ϭ 2.2 Hz). Ϫ 13C NMR
(CDCl3): δ ϭ 211.6 (CϭO), 155.4 (Cϭ), 107.6 (Cϭ), 43.9 (2 C, d),
39.5 (2 C, d), 37.2 (2 C, t), 30.7 (2 C, (t), 25.6 (t). Ϫ UV/Vis
(CH2Cl2): λmax (log ε) ϭ 222 nm (3.8), 256 (3.98). Ϫ IR (KBr):
ν˜ ϭ 3032 cmϪ1 (w), 3017 (w), 2967 (w), 2950 (w), 2938 (m), 2916
(w), 2900 (w), 2866 (w), 1769 (vs). Ϫ MS (70 eV); m/z (%): 239 (1),
238 [M•ϩ] (10), 184 (12), 183 (88), 182 (30), 163 (9), 136 (18), 135
(57), 134 (15), 121 (14), 110 (11), 109 (100), 108 (20). Ϫ C12H14S2O
(238.36): calcd. C 60.47, H 5.92, S 26.90; found C 60.39, H 5.88, S
26.89. Ϫ 28: M.p. 125°C. Ϫ Rf (silica gel, pentane/diethyl ether,
1
1:2) ϭ 0.42. Ϫ H NMR ([D6]DMSO): δ ϭ 7.35Ϫ7.23 (4 H, m),
7.12Ϫ7.06 (4 H, m), 5.01 (1 H, s), 4.41 (1 H, s), 2.88 (1 H, m), 2.46
(1 H, s), 2.36 (1 H, d, J ϭ 11.4 Hz), 2.29 (1 H, s), 2.15 (1 H, s),
1.99 (1 H, s), 1.39 (1 H, d, J ϭ 11.3 Hz), 1.13 (1 H, d, J ϭ 11.4
Hz). Ϫ 13C NMR (D6]DMSO): δ ϭ 208.0 (s), 153.8 (s), 153.1 (s),
130.2 (d), 127.8 (d), 127.5 (d), 127.4 (d), 123.1 (s), 122.9 (s), 122.6
(d), 122.3 (d), 116.0 (d), 115.8 (d), 88.6 (s), 46.2 (d), 44.5 (d), 42.74
(d), 42.66 (d), 39.3 (d), 34.0 (t), 33.5 (t). Ϫ UV/Vis (CH2Cl2): λmax
(log ε) ϭ 222 nm (3.88), 244 (3.98), 286 (3.51). Ϫ IR (KBr): ν˜ ϭ
3397 cmϪ1 (vs), 3010 (s), 2938 (m), 2878 (m), 2361 (w), 1751 (vs),
1598 (m), 1577 (m), 1479 (vs), 1456 (vs). Ϫ MS (70 eV); m/z (%):
318 [M•ϩ] (1), 182 (59), 181 (100), 180 (1), 153 (2), 152 (13), 151
(3), 150 (1). Ϫ C21H18O2 (302.37): calcd. C 79.23, H 5.70; found C
79.24, H 5.72.
1
9:1) ϭ 0.44. Ϫ H NMR (200 MHz, CDCl3): δ ϭ 3.08 (4 H, m),
2.83Ϫ2.77 (8 H, m), 2.20Ϫ2.10 (4 H, m), 1.58Ϫ1.55 (4 H, m). Ϫ
13CϪNMR (50.32 MHz, CDCl3): δ ϭ 159.9 (2 C, Cϭ), 103.4 (2
C, Cϭ), 42.0 (2 C, t), 41.9 (4 C, d), 30.8 (4 C, t), 25.9 (2 C, t). Ϫ
UV/Vis (CH2Cl2): λmax (log ε) ϭ 230 nm (3.5), 268 (3.7). Ϫ IR
(KBr): ν˜ ϭ 3004 cmϪ1 (w), 2947 (m), 2927 (s), 2905 (m), 2861 (w),
2823 (w), 1638 (w), 1421 (m). Ϫ MS (70 eV); m/z (%): 341 (9),
340 [M•ϩ] (23), 295 (100), 265 (13). Ϫ HRMS: calcd. for C16H20S4
340.0448; found 340.0448.
6-(9H-Xanthen-9-ylidene)tricyclo[3.3.0.03,7]octane-2-one (25): The
preparation of 25 was accomplished analogously to that of 19.
Starting materials: 6.4 g (20.0 mmol) of 24, 8.14 mL (87.0 mmol)
of POCl3 and 102 mL (1.3 mmol) of pyridine. This reaction yielded
3.3 g (56%) of 25 as a colorless solid, 169°C. Ϫ Rf (silica gel, pen-
Diethyl
2-(6-Oxotricyclo[3.3.0.03,7]octan-2-ylidene)propanedioate
(29) and Tetraethyl 2,2Ј-(Tricyclo[3.3.0.03,7]octane-2,6-diylidene)bis-
(propanedioate) (30): The reaction of 5 with diethyl malonate was
carried out analogously to the reaction of 4 with 14. Starting mate-
rials: 544 mg (4.0 mmol) of 5, 1.22 mL (8.0 mmol) of 14 in 4.0 mL
of CCl4. This reaction yielded 347 mg (31%) of 29 and 426 mg
(25%) of 30 as colorless oils. Separation was accomplished by silica
gel chromatography (pentane/diethyl ether, 1:1). Ϫ 29: Rf (silica gel,
pentane/diethyl ether, 1:1) ϭ 0.48. Ϫ 1H NMR (CD2Cl2): δ ϭ 4.26
1
tane/CH2Cl2 1:1) ϭ 0.26. Ϫ H NMR (CDCl3): δ ϭ 7.43Ϫ7.09 (8
H, m), 3.57 (2 H, s, br.), 2.41 (2 H, s, br.), 1.82Ϫ1.74 (4 H, m). Ϫ
13C NMR (CDCl3): δ ϭ 211.8 (s), 153.5 (2 C, s), 148.3 (2 C, s),
128.0 (2 C, d), 126.5 (2 C, d), 124.9 (s), 123.3 (2 C, d), 116.6 (2 C,
d), 113.3 (s), 44.0 (2 C, d), 38.6 (2 C, d), 37.1 (2 C, t). Ϫ UV/Vis
(CH2Cl2): λmax (log ε) ϭ 224 nm (4.49), 256 (4.09), 312 (4.01). Ϫ
IR (KBr): ν˜ ϭ 3025 cmϪ1 (m), 2970 (m), 2932 (m), 2866 (m), 1771
(vs), 1593 (w), 1566 (w), 1448 (vs). Ϫ MS (70 eV); m/z (%): 300
[M•ϩ] (18), 299 (12), 293 (25), 280 (25), 271 (22), 269 (11), 255 (17),
245 (12), 244 (13), 243 (26), 242 (20), 240 (11), 231 (10), 219 (10),
218 (22), 217 (24), 212 (17), 205 (10), 193 (13), 182 (23), 181 (100).
Ϫ HRMS: calcd. for C21H16O2 300.1166; found 300.1158.
3
(4 H, dq, J ϭ 7.1, J ϭ 2.8 Hz), 3.55Ϫ3.54 (2 H, m), 2.41Ϫ2.40 (2
H, m), 1.81Ϫ1.72 (4 H, m), 1.35Ϫ1.30 (6 H, t, 3J ϭ 7.1 Hz). Ϫ 13C
NMR (CD2Cl2): δ ϭ 210.1 (s), 171.2 (s), 165.0 (2 C, s), 114.1 (s),
61.5 (2 C, t), 43.9 (2 C, d), 40.3 (2 C, d), 35.8 (2 C, t), 14.3 (2 C,
q). Ϫ UV/Vis (CH2Cl2): λmax (log ε) ϭ 232 nm (3.75). Ϫ IR (KBr):
ν˜ ϭ 2983 cmϪ1 (w), 1779 (s), 1719 (vs), 1678 (w), 1461 (w). Ϫ 30:
1
Rf (silica gel, pentane/diethyl ether, 1:1) ϭ 0.12. Ϫ H NMR (200
6-(1H-Cyclopropa[b]naphthalen-2-ylidene)tricyclo[3.3.0.03,7]octan-2-
one (26): The preparation of 26 was accomplished analogously to
that of 10. Starting materials: 360 mg (1.2 mmol) of 7 and 164 mg
MHz, CDCl3): δ ϭ 4.18 (8 H, dq, 3J ϭ 7.1, J ϭ 1.1 Hz), 3.38 (4
H, m), 1.65 (4 H, m), 1.24 (12 H, t, 3J ϭ 7.1 Hz). Ϫ 13C NMR
(50.32 MHz, CDCl3): δ ϭ 173.4 (2 C, s), 164.6 (4 C, s), 111.5 (2
(1.2 mmol) of 5. This reaction yielded 192 mg (62%) of 26 as a pale C, s), 60.9 (4 C, t), 41.9 (4 C, d), 39.3 (2 C, t), 14.0 (4 C, q). Ϫ UV/
yellow solid, m.p. 105°C. Ϫ Rf (silica gel, pentane/diethyl ether,
4:1) ϭ 0.44. Ϫ H NMR (CDCl3): δ ϭ 7.85 (2 H, dd, J ϭ 6.2, J ϭ
3.3 Hz), 7.46 (2 H, td, J ϭ 6.3, J ϭ 3.0 Hz), 7.39 (2 H, s), 3.38 (2
Eur. J. Org. Chem. 1999, 73Ϫ81
Vis (CH2Cl2): λmax (log ε) ϭ 238 nm (4.38). Ϫ IR (neat film): ν˜ ϭ
2982 cmϪ1 (m), 2906 (w), 1720 (vs), 1676 (s), 1463 (w), 1390 (w),
1368 (m). Ϫ MS (70 eV); m/z (%): 420 [M•ϩ] (4), 375 (21), 374 (40),
1
79

G. Fritzsche, R. Gleiter, H. Irngartinger, T. Oeser
FULL PAPER
329 (50), 328 (87), 301 (25), 300 (28), 283 (15), 282 (54), 256 (17),
255 (30), 254 (20), 227 (14), 215 (10), 214 (15), 210 (19), 199 (10),
N 15.13. Ϫ Compound 32: M.p. 163°C. Ϫ Rf (silica gel, pentane/
diethyl ether, 1:1) ϭ 0.15. Ϫ H NMR (CDCl3): δ ϭ 3.81Ϫ3.72 (2
1
155 (10), 128 (12), 127 (12), 115 (35), 107 (30), 105 (100). Ϫ H, m), 3.17Ϫ2.95 (4 H, m), 2.68Ϫ2.57 (2 H, m), 1.99Ϫ1.86 (2 H,
C22H28O8 (420.46): calcd. C, 62.85; H 6.71; found C 62.65; H 6.82.
m). Ϫ 13C NMR (CDCl3): δ ϭ 188.8 (2 C, s), 111.1 (2 C, s), 111.0
(2 C, s), 83.5 (2 C, s), 52.1 (2 C, d), 36.2 (2 C, t), 29.3 (2 C, t). Ϫ
UV/Vis (CH2Cl2): λmax (log ε) ϭ 248 nm (4.42). Ϫ IR (KBr): ν˜ ϭ
2956 cmϪ1 (w), 2921 (w), 2360 (w), 2233 (s), 1616 (s). Ϫ MS (70
eV); m/z (%): 234 [M•ϩ] (10), 169 (14), 144 (10), 143 (100). Ϫ
HRMS: calcd. for C14H10N4 234.0906; found 234.0905.
2-(6-Oxotricyclo[3.3.0.03,7]octan-2-ylidene)propanedinitrile
(31)
and 2,6-Bis(dicyanomethylene)bicyclo[3.3.0]octane (32): A mixture
1.5 g (11.0 mmol) of 5, 3.5 g (53.0 mmol) of malononitrile, 3.5 g
(46.0 mmol) of ammonium acetate, and 10.6 mL acetic acid in 150
mL of toluene was refluxed for 2 h in a DeanϪStark apparatus,
then stirred for 18 h at 80°C. After addition of 5% of aqueous [6-(Fluoren-9-ylidene)tricyclo[3.3.0.03,7]octan-2-ylidene]-1,3-dithian
NaHCO3 the layers were separated. Extraction was effected twice
with toluene and the combined organic layers were washed with
water, dried with MgSO4, and the solvent evaporated. Purification
of the residue by silica gel chromatography (elution with pentane/
diethyl ether, 4:1) gave 1.5 g (75%) of 31 as a colorless solid. When
reflux was continued for 24 h, the yield of 31 decreased and 72 mg
(3%) of 32 was obtained as colorless crystals. Compound 31: M.p.
118°C. Ϫ Rf (silica gel, pentane/diethyl ether, 1:1) ϭ 0.28. Ϫ 1H
NMR (CDCl3): δ ϭ 3.44 (2 H, d, 3J ϭ 1.5 Hz), 2.62 (2 H, dd, 3J ϭ
(33): To a magnetically stirred solution of 2-trimethylsilyl-1,3-dithi-
ane (6) (258 mL, 1.4 mmol) in 10 mL of THF was added 0.9 mL
(1.4 mmol) of a solution of 1.6  nBuLi in n-hexane at Ϫ78°C.
The solution was allowed to warm up to 0°C. After cooling to
Ϫ78°C, the ketone 23 (160 mg, 0.6 mmol) in 10 mL of THF was
added and the reaction mixture was maintained at Ϫ78°C for 1 h,
then warmed to 0°C again. The reaction mixture was hydrolyzed
with water, the solvent evaporated and the residue directly chroma-
tographed on silica gel with pentane/diethyl ether (9:1) to yield 129
mg (60%) of 33 as a pale yellow solid: Ϫ Rf (silica gel, pentane/
diethyl ether, 9:1) ϭ 0.39. Ϫ 1H NMR (200 MHz, CD2Cl2): δ ϭ
7.95Ϫ7.91 (2 H, m), 7.80Ϫ7.76 (2 H, m), 7.37Ϫ7.29 (4 H, m),
3.96Ϫ3.94 (2 H, m), 3.28Ϫ3.27 (2 H, m), 2.88Ϫ2.82 (4 H, m),
2.20Ϫ2.13 (2 H, m), 1.71Ϫ1.69 (4 H, m). Ϫ 13C NMR (50.32 MHz,
3
2
3
5.3, J ϭ 2.6 Hz), 1.96 (2 H, dd, J ϭ 12.5, J ϭ 1.6 Hz), 1.81 (2
2
3
H, dd, J ϭ 12.6, J ϭ 2.3 Hz). Ϫ 13C NMR (CDCl3): δ ϭ 205.9
(s), 190.6 (s), 110.6 (2 C) (s), 74.8 (s), 43.4 (2 C) (d), 42.3 (2 C) (d),
35.4 (2 C) (t). Ϫ UV/Vis (CH2Cl2): λmax (log ε) ϭ 230 nm (4.26).
Ϫ IR (KBr): ν˜ ϭ 3426 cmϪ1 (s, br), 3050 (w), 2951 (w), 2877 (w),
2240 (s), 1776 (vs), 1645 (s), 1462 (w). Ϫ MS (70 eV); m/z (%): 185 CD2Cl2): δ ϭ 160.0 (s), 159.87 (s), 139.7 (2 C, s), 139.2 (2 C, s),
(2), 184 [M•ϩ] (12), 156 (22), 141 (28), 129 (39), 128 (40), 102 (16),
127.1 (2 C, d), 126.9 (2 C, d), 126.6 (s), 125.9 (s), 123.5 (2 C, d),
91 (21), 78 (10), 76 (12), 75 (12), 65 (10), 55 (100). Ϫ C11H8ON2 119.8 (2 C, d), 42.6 (2 C, d), 41.7 (2 C, d), 41.6 (2 C, t), 31.2 (2 C,
(184.20): calcd. C 71.73, H 4.38, N 15.21; found C 71.45, H 4.46,
t), 26.3 (t). Ϫ UV/Vis (CH2Cl2): λmax (log ε) ϭ 236 nm (4.31), 248
Table 2. Crystallographic data of 18, 19, 24, 27, 31, and 32
Compound
18
19
24
27
31
32
Empirical formula C21H18
C21H18
O
C21H18O3
318.4
C12H14OS2
238.4
C11H8N2O
184.2
C14H10N4
234.3
Molecular mass
[g/mol]
270.4
286.4
Crystal size [mm] 0.48ϫ0.26ϫ0.22 0.5ϫ0.4ϫ0.26
0.4ϫ0.25ϫ0.25
colorless
prism
P21/c
0.35ϫ0.25ϫ0.2
colorless
prism
P21/n
7.121(1)
19.257(3)
8.296(1)
90
0.5ϫ0.48ϫ0.45
0.4ϫ0.15ϫ0.1
colorless
Crystal color
Crystal shape
Space group
colorless
needle
Pbca
colorless
fragment
colorless
polyhedron
P41212
6.812(1)
6.812(1)
19.078(3)
90
prism
¯
¯
P1
P1
˚
a [A]
16.1601(8)
9.1316(5)
19.307(1)
90
11.2484(3)
11.5577(3)
13.7313(3)
91.274(1)
105.926(1)
118.640(1)
1481.4(1)
1.28
14.726(2)
9.947(1)
10.698(2)
90
7.671(1)
11.834(2)
14.884(2)
110.99(1)
92.42(1)
100.37(1)
1232.5(3)
1.26
˚
b [A]
˚
c [A]
α [°]
β [°]
γ [°]
90
90
106.86(1)
90
95.59(1)
90
90
90
3
˚
V [A ]
2849.1(3)
1.26
1499.7(4)
1.41
1132.2(2)
1.40
885.3(2)
1.38
Dcalcd. [Mg/m3]
Z
F(000)
8
4
4
4
4
4
1152
608
672
504
384
488
Temperature [K]
hmin/hmax
kmin/kmax
lmin/lmax
200
200
223
223
223
223
Ϫ18/18
Ϫ10/11
Ϫ22/18
2.1Ϫ25.5
0.07
Ϫ11/12
Ϫ13/11
Ϫ16/14
1.6Ϫ25.6
0.08
Ϫ18/19
0/13
0/9
0/9
Ϫ10/10
Ϫ15/14
0/19
0/25
0/9
Ϫ14/0
2.5Ϫ28.0
0.09
Ϫ10/10
2.1Ϫ28.0
0.44
0/25
Θ range [°]
2Ϫ28
0.09
2.7Ϫ28.0
0.08
Ϫ
µ [mmϪ1
Tmax [%]
Tmin [%]
]
Ϫ
Ϫ
97.8
Ϫ
Ϫ
99.1
Ϫ
Ϫ
85.4
90.5
Ϫ
Refl. collected
Refl. unique
Refl. observed
[I > 2σ (I)]
Variables
(∆/σ)max
R
12190
6690
3776
2922
924
6149
2489
4715
3583
2718
858
5923
1862
3974
2462
2246
821
3247
262
541
289
192
82
405
< 0.01
0.043
0.094
1.10
< 0.01
0.041
0.098
1.06
< 0.01
0.048
0.129
1.09
< 0.01
0.039
0.110
1.26
< 0.01
0.033
0.088
1.11
< 0.01
0.047
0.097
1.10
Rw
S (Gof)
Ϫ3
˚
(∆ρ)max [e A
]
]
0.22
Ϫ0.18
0.43
Ϫ0.19
0.33
Ϫ0.27
0.59
Ϫ0.34
0.18
Ϫ0.30
0.23
Ϫ0.25
Ϫ3
˚
(∆ρ)min [e A
80
Eur. J. Org. Chem. 1999, 73Ϫ81

Syntheses of Donor–Acceptor-Substituted 2,6-Stellanes
FULL PAPER
(4.09), 258 (4.04), 286 (3.92), 294 (3.96), 308 (3.88), 322 (3.93), 366 radiation, graphite monochromator, ω-2Θ scan). Intensities were
(3.03). Ϫ IR (KBr): ν˜ ϭ 2929 cmϪ1 (m), 1662 (s), 1445 (vs), 1268 corrected for Lorentz and polarisation effects. An empirical ab-
(m). Ϫ MS (70 eV); m/z (%): 388 (15), 387 (30), 386 (100) [M•ϩ].
Ϫ HRMS: calcd. for C25H22S2 386.11630; found 386.11596.
sorption correction was performed in the case of 19 and a numeri-
cal absorption correction was applied on compound 27. All struc-
tures were solved by direct methods (SHELXS-86 and SHELXS-
97).[14] The structural parameters of the non-hydrogen atoms were
refined anisotropically and the parameters of the hydrogen atoms
were refined isotropically according to a full-matrix least-squares
technique (F2). Refinement was carried out with SHELXL-93 and
SHELXL-97.[15] Crystallographic data (excluding structure factors)
for the structures reported in this paper have been deposited with
the Cambridge Crystallographic Data Centre as supplementary
publication nos. CCD C-101933 to -101938 for 18, 19, 24, 27,
31, and 32, respectively. Copies of the data can be obtained free
of charge on application to CCDC, 12 Union Road, Cambridge
CB2 1EZ, U K [Fax: int. code ϩ 44(1223)336-033, E-mail:
deposit@ccdc.cam.ac.uk].
Diethyl 2-[6-(Fluoren-9-ylidene)tricyclo[3.3.0.03,7]octan-2-ylidene]-
propanedioate (34): The reaction of 23 with diethyl malonate was
carried out in an analogous way to the reaction of 4 with 14. Start-
ing materials: 650 mg (2.3 mmol) of 23, 0.5 mL (3.5 mmol) of 14
in 40 mL THF. This reaction yielded 213 mg (22%) of 34 as a pale
yellow solid, m.p. 53°C. Ϫ Rf (silica gel, benzene) ϭ 0.33. Ϫ 1H
NMR (CD2Cl2): δ ϭ 7.97Ϫ7.94 (2 H, m), 7.83Ϫ7.80 (2 H, m),
3
2
7.40Ϫ7.31 (4 H, m), 4.29 (4 H, dq, J ϭ 7.1, J ϭ 1.9 Hz), 4.05 (2
3
H, m), 3.59 (2 H, m), 1.86 (4 H, s), 1.36 (6 H, t, J ϭ 7.1 Hz). Ϫ
13C NMR (CD2Cl2): δ ϭ 174.5 (s), 165.2 (2 C, s), 158.3 (s), 139.9
(2 C, s), 139.0 (2 C, s), 127.2 (2 C, d), 127.1 (2 C, d), 123.6 (2 C,
d), 119.9 (2 C, d), 119.8 (s), 111.6 (s), 61.3 (2 C, t), 43.1 (2 C, d),
41.4 (2 C, d), 40.4 (2 C, t), 14.3 (2 C, q). Ϫ UV/Vis (CH2Cl2): λmax
(log ε) ϭ 236 nm (4.71), 250 (4.47), 258 (4.49), 282 (4.49), 292
(4.43), 304 (4.34), 318 (4.37). Ϫ IR (KBr): ν˜ ϭ 2977 cmϪ1 (m),
1722 (s), 1663 (m), 1445 (m), 1366 (w), 1239 (s), 1221 (s). Ϫ MS
(70 eV); m/z (%): 426 [M•ϩ] (20), 381 (46), 380 (100), 306 (11), 279
(17), 278 (11), 277 (12), 266 (11), 216 (11), 215 (73), 166 (12), 165
(82), 78 (22). Ϫ HR MS: calcd. for C28H 26O4 426.1831; found
426.1821.
Acknowledgments
We are grateful to the Volkswagenstiftung, the Fonds der Che-
mischen Industrie and the BASF Aktiengesellschaft in Ludwigs-
hafen for financial support. We thank U. Wiesinger and Dr. F.
Rominger for crystal preparation and help collecting the X-ray
data.
Diethyl 2-[6-(9H-Xanthen-9-ylidene)tricyclo[3.3.0.03,7]octan-2-yl-
idene]propanedioate (35): 1.1 mL of TiCl4 (10.0 mmol) was added
dropwise at 0°C to a magnetically stirred mixture of 8.0 mL of
CCl4 and 30.0 mL of THF. To the yellow precipitate which was
formed, a solution of 0.8 mL (5.0 mmol) of diethyl malonate and
1.0 g (3.3 mmol) of 25 in 40 mL of THF was added within 15 min
at 0°C. This addition was followed by 1.6 mL (19.8 mmol) of pyri-
dine in 5 mL of THF. The reaction mixture was allowed to warm
up to room temp. and stirred for 3 d before it was poured into ice-
cold water. Extraction was effected with ethyl acetate (ϫ 3). The
combined organic layers were washed with 5% aqueous NH4Cl and
with brine. The solvent in the separated organic layer was evapo-
rated and, after purification of the residue by silica gel chromatog-
raphy (benzene), 303 mg (21%) of 35 was obtained as a pale yellow
solid, m.p. 54°C. Ϫ Rf (silica gel, benzene) ϭ 0.34. Ϫ 1H NMR
(CD2Cl2): δ ϭ 7.52Ϫ7.14 (8 H, m), 4.25 (4 H, m), 3.54 (2 H, m),
[1]
G. L. Closs, J. R. Miller, Science 1988, 240, 440; J. R. Miller,
Nouv J. Chem. 1987, 11, 83; M. R. Wasielewski, Chem. Rev.
1992, 92, 435; K. D. Jordan, M. N. Paddon-Row, Chem. Rev.
1992, 92, 935 and references in these reviews.
[2] [2a]
R. Gleiter, O. Borzyk, Angew. Chem. 1995, 107, 1094; An-
[2b]
gew. Chem. Int. Ed. Engl. 1995, 34, 1001. Ϫ
R. Gleiter, G.
Fritzsche, O. Borzyk, T. Oeser, F. Rominger, H. Irngartinger, J.
Org. Chem. 1998, 63, 2878.
[3]
R. Gleiter, H. Lange, O. Borzyk, J. Am. Chem. Soc. 1996, 118,
4889; H. Lange, R. Gleiter, G. Fritzsche, J. Am. Chem. Soc.
1998, 120, 6563.
[4]
[5]
B. Gaa, R. Gleiter, to be published.
R. Gleiter, B. Kissler, C. Ganter, Angew. Chem. 1987, 99, 1292;
Angew. Chem. Int. Ed. Engl. 1987, 26, 1252.
R. R. Sauers, K. W. Kelly, B. R. Sickles, J. Org. Chem. 1972,
37, 537.
[6]
[7]
[8]
2
3
M. Nakazaki, K. Naemura, H. Harada, H. Narutaki, J. Org.
Chem. 1982, 47, 3470.
3.48Ϫ3.47 (2 H, m), 1.76 (2 H, dd, J ϭ 16.6, J ϭ 10.8 Hz), 1.75
2
3
3
(2 H, dd, J ϭ 16.0, J ϭ 10.8 Hz), 1.33 (6 H, t, J ϭ 7.1 Hz). Ϫ
13C NMR (CD2Cl2): δ ϭ 175.3 (s), 165.3 (2 C, s), 153.8 (2 C, s),
151.8 (s), 128.0 (2 C, d), 127.0 (2 C, d), 125.5 (2 C, d), 123.5 (2 C,
d), 116.6 (2 C, d), 111.3 (2 C, d), 61.2 (2 C, t), 42.9 (2 C, d), 41.2
(2 C, d), 41.1 (2 C, t), 14.3 (2 C, q). Ϫ UV/Vis (CH2Cl2): λmax (log
ε) ϭ 226 nm (4.62), 258 (4.26), 316 (4.20). Ϫ IR (KBr): ν˜ ϭ 3031
cmϪ1 (w), 2978 (m), 2868 (w), 1718 (vs), 1669 (s), 1592 (w), 1566
(w), 1474 (m), 1447 (s). Ϫ MS (70 eV); m/z (%): 443 [M•ϩϩ1] (10),
442 [M•ϩ] (35), 398 (11), 397 (53), 396 (100). Ϫ HRMS: calcd. for
C28H26O5 442.1780; found 442.1781.
R. Gleiter, B. Gaa, C. Sigwart, H. Lange, O. Borzyk, F. Ro-
minger, H. Irngartinger, T. Oeser, Eur. J. Org. Chem. 1998, 171.
D. Seebach, M. Kolb, B. T. Gröbel, Chem. Ber. 1973, 106, 2277.
B. Halton, Chem. Rev. 1989, 89, 1161; Pure Appl. Chem. 1990,
62, 541 and references cited.
[9]
[10]
[11]
B. Halton, A. J. Kay, Z. Zhi-mei, J. Chem. Soc., Perkin Trans.
1 1993, 2239.
[12]
[13]
D. J. Peterson, J. Org. Chem. 1968, 33, 780.
V. Siemund, H. Irngartinger, C. Sigwart, B. Kissler, R. Gleiter,
Acta Crystallogr., Sect. C 1993, 49, 57.
[14]
[15]
[16]
G. M. Sheldrick, SHELXS-86 and SHELXS-97, Universität
Göttingen, Germany, 1997.
G. M. Sheldrick, SHELXL-93 and SHELXL-97, Universität
Göttingen, Germany, 1997.
X-ray Crystallographic Studies: Crystal data are given in Table 2.
The reflections of compounds 18 and 19 were collected with a Sie-
mens P4 diffractometer (ω scans) and the data of 24, 27, 31, and
32 were collected with a Nonius-CAD4-diffractometer (Mo-Kα
E. Keller, SCHAKAL92, Universität Freiburg, Germany, 1992.
Received June 16, 1998
[O98266]
Eur. J. Org. Chem. 1999, 73Ϫ81
81