2-Hydroxybenzocyclobutenone ethylene dithioacetals as precursors of highly substituted 1,4-Dihydronaphthalenes

Article abstract of DOI:10.1002/ejoc.200801101

1,4-Dihydronaphthalenes 2, 9, and 11 with a spiro-connected 1,3-dithiolane ring as well as tetrahydronaphthalenes 15, 17, and 19 have been obtained from o-quinodimethanes 3 and alkynes 4, naphthoquinones 10, or alkenes 14 and 16. Benzocyclobutenol 6 is no

Full text of DOI:10.1002/ejoc.200801101

FULL PAPER
DOI: 10.1002/ejoc.200801101
2-Hydroxybenzocyclobutenone Ethylene Dithioacetals as Precursors of Highly
Substituted 1,4-Dihydronaphthalenes
Konstantin Benda,[a] Wilko Regenhardt,[a] Ernst Schaumann,*[a] and Gunadi Adiwidjaja[b]
Keywords: Quinodimethanes / Alkynes / Cycloaddition / Electrocyclic reactions / Regioselectivity
1,4-Dihydronaphthalenes 2, 9, and 11 with a spiro-connected
1,3-dithiolane ring as well as tetrahydronaphthalenes 15, 17,
and 19 have been obtained from o-quinodimethanes 3 and
alkynes 4, naphthoquinones 10, or alkenes 14 and 16. Benzo-
cyclobutenol 6 is not an appropriate quinodimethane precur-
sor as it readily rearranges to phthalaldehyde derivative 7.
However, silyl ether 8, silyl ether 13, obtained by the hydro-
ated in situ by DIBAL reduction of 5, are useful sources of
the corresponding quinodimethanes. The use of 3b,c gives a
reversal of regioselectivity compared with 3d in the cycload-
dition with propriolate 4a (product 9a vs. 2a). Naphthoqui-
none 10 reacts in the cycloaddition with 3b,c through its
C2=C3 bond or through a C=O unit to give 11 and 12.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
silylation of cyclobutenol 5, or aluminium alkoxide 3d, gener- Germany, 2009)
Introduction
1,4-Dihydronaphthalenes have been called a “privileged”
structural class because of their diverse biological activi-
ties[1] and thus there is continued interest in their synthesis.
The Diels–Alder reaction of dienes with arynes[1] and, in
particular, the reaction of o-quinodimethanes with alkynes
are the most prominent strategies used in the synthesis of
1,4-dihydronaphthalenes.[2] In addition to photoenoli-
zation,[3] reactive o-quinodimethanes are mostly generated
in situ by the electrocyclic ring-opening of benzocyclobut-
enes.[4] We are interested in 1,4-dihydronaphthalenes be-
cause we envisage spiro derivatives 2 as intermediates en
route to thionaphthoquinones 1 (Scheme 1). In fact, we
have previously shown that 1,3-dithiolane S-oxides can be
Scheme 1. A potential route to thionaphthoquinones.
converted into thioaldehydes and -ketones by silylation and
subsequent deprotonation.[5] This means that spiro com-
pounds 2 should be only two oxidation steps away from the
target molecules 1 and with appropriately chosen substitu-
ents, even thio analogues of vitamin K might be available.
The obvious route to dihydronaphthalenes 2 appears to
be the [4+2] cycloaddition of functionalized o-quinodime-
thanes 3 with alkynes 4 (Scheme 1). However, it turns out
that dienol 3a cannot be employed in Diels–Alder chemistry
because of its low stability. In contrast, its silyl ether deriva-
tive 3b, the in-situ generated silyl ether 3c, and the alumin-
ium salt 3d are useful dienes in cycloaddition reactions with
alkynes 4 and also with alkenes.[6]
Results and Discussion
The readily available benzocyclobutenedione monothio-
ketal 5[7] can be smoothly reduced to alcohol 6 by DIBAL.
After work-up 6 is obtained in 77% yield, but within min-
utes at room temperature it rearranges to aldehyde 7 by
electrocyclic ring-opening and a subsequent [1,5] hydrogen
shift (Scheme 2). This ready rearrangement prevents the use
of benzocyclobutenol 6 in Diels–Alder chemistry.
[a] Department of Organic Chemistry, Clausthal University of
Technology,
Leibnizstrasse 6, 38678 Clausthal-Zellerfeld, Germany
Fax: +49-5323-722858
E-mail: Ernst.schaumann@tu-clausthal.de
[b] Mineralogisch-Petrographisches Institut, Universität Hamburg,
Grindelallee 48, 20146 Hamburg, Germany
Scheme 2. Synthesis and rearrangement of benzocyclobutenol 6.
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Eur. J. Org. Chem. 2009, 1016–1021
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Highly Substituted 1,4-Dihydronaphthalenes
One way to suppress this reaction, at least to some ex-
tent, is to trap the alcohol 6 as the silyl ether 8. This com-
pound is remarkably stable and may be stored at room tem-
perature for at least 3 days. Silyl ether 8 exists in equilibrium
with the corresponding ring-opened product 3b (Scheme 3).
Thus, due to the different colors of the two compounds, a
color change can be observed on going from 3b (deep yel-
low at room temperature) to 8 (colorless at 0 °C) on cool-
ing.
Figure 1. Crystal structure of 12a (ORTEP plot).
Scheme 3. Stabilization of benzocyclobutenol 6 as the silyl ether 8
and its electrocyclic ring-opening.
cessful hydrosilylation of 5, affording silyl ether 13 in good
yield and free from aldehyde 7. In a convenient one-pot
procedure alkyne dienophiles can be added to the crude si-
lyl ether to provide naphthalenes 9c,d directly (Scheme 5).
Again, the cycloaddition certainly involves intermediate 3c,
which also reacts with tetracyanoethene (14) to give Diels–
Alder adduct 15a. With 1,4-naphthoquinone (10), as with
the silyl ether 8/o-quinodimethane 3b system, the competing
formation of cycloadducts 11b and 12b (cf. Scheme 4) is
observed in a similar ratio of 1:1.5 (Scheme 5).
TBS ether 8 undergoes Diels–Alder reactions with elec-
tron-deficient alkynes 4 in good yields, clearly reacting in
its ring-opened form 3b (Scheme 4). Thus, stirring 8 with
an alkyne 4 at room temperature in toluene leads to naph-
thalenes 9a,b with the regiochemistry shown in Scheme 4.
Scheme 4. Reaction of silyl ether 8 with alkynes 4 or 1,4-naphtho-
quinone 10.
Particularly interesting is the reaction of silyl enol ether
8 with 1,4-naphthoquinone (10). Here, the expected tetra-
cyclic silyl enol ether 11a is only the minor product; the
major product is the isochromane 12a generated by a het-
ero-Diels–Alder reaction (Scheme 4). The structure of 12a
may be delineated primarily from the NMR spectroscopic
data, but it is unambiguously supported by a single-crystal
X-ray structure determination (Figure 1). This cycload-
dition behavior is typical of light-induced reactions,[8] but
several experiments in the dark led to exactly the same
product ratio of 1:2. So far, only in one case are thermally
induced hetero-Diels–Alder products of benzoquinones de-
scribed in the literature.[9]
Scheme 5. Reaction of silyl ether 13 with alkynes 4, 1,4-naphtho-
quinone (10), or tetracyanoethene (14).
In an alternate approach, which also excludes the forma-
tion of 7, the alcohol 6 was not isolated after the reaction
These successful applications of silyl dienol ether 8 called of 5 with DIBAL, but employed as the aluminium salt 3d
for a more reliable synthesis that would prevent any forma- in reactions with alkynes 4. With acetylenedicarboxylate
tion of the rearrangement product 7. With this in mind, this gives the [4+2] cycloadduct 2b in about the same yield
hydrosilylation of the carbonyl unit in 1 seemed promising. as starting from silyl ether 8, but interestingly a different
Unfortunately, the use of tert-butyldimethylsilane in combi- product 2a with propiolate. This turned out to be the re-
nation with transition-metal catalysts (Re-,[10] Ru-,[11] or gioisomer of 9a. The structure was assigned on the basis of
Rh-based[12]) or several Lewis acids[13] was not successful. the pattern of proton couplings in the NMR spectra. The
1
However, the use of dimethyl(phenyl)silane (DMPS-H) and decisive feature is the H NMR signal of the single proton,
tris(pentafluorophenyl)borane[14] as catalyst led to the suc- which is observed as a singlet for 2a but as a doublet (J =
Eur. J. Org. Chem. 2009, 1016–1021
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K. Benda, W. Regenhardt, E. Schaumann, G. Adiwidjaja
FULL PAPER
2.9 Hz) for 9a. The regiochemical dichotomy of these reac- γ-lactone formation has previously been observed by
tions leads us to assume that 9a,b are formed in a classic Sammes and co-workers.[3a,3b]
concerted Diels–Alder reaction, but that in the formation
of 2a a Michael-type pathway with subsequent ring-closure
directs the electron-withdrawing group adjacent to the hy-
droxy group.
Conclusions
The ring-opening of alcohol 6 to monoprotected phthal-
aldehyde 7 can be avoided by using silyl ethers 8 and 13 in
the Diels–Alder reactions. This approach is complemented
by employing aluminium salt 3d in the cycloaddition reac-
tions, which gives similar yields in the cycloaddition reac-
tions with alkynes 4. However, a striking feature of these
latter reactions is the reversal of the regioselectivity as com-
pared with the use of silyl ethers 8 and 13. The success of
these model reactions is encouraging in the pursuit of spiro
compounds 2 as intermediates in thioquinone synthesis.
Following the successful reactions with alkynes 4, we in-
vestigated the reaction of the aluminium salt 3d with a wide
range of electron-deficient alkenes. Some interesting prod-
ucts are reported in Scheme 6. In all cases, endo products
with a cis arrangement of the alcohol and the neighboring
functional group are isolated. The cycloaddition reactions
of 3d all proceed at room temperature, which indicates that
the benzo-annulated diene unit in 3d is more reactive than
the corresponding acyclic species, which is generated from
cyclobutenyl silyl ethers and requires refluxing toluene for
some reaction partners.[15]
Experimental Section
General: All reactions were carried out under nitrogen. 1H and 13
C
NMR spectra were recorded with Bruker DPX-200 and AMX-400
instruments in CDCl3 as solvent. Chemical shifts were measured in
δ (ppm) and coupling constants J in Hz. TMS was used as reference
for 1H NMR spectra (δ = 0.00 ppm). The solvent peak was used
as the reference for 13C NMR spectra (δ = 77.00 ppm). To assign
the number of substituents attached to a specified carbon, each
carbon is described as + (primary or tertiary carbon), – (secondary
carbon) or o (quaternary carbon), as determined by the DEPT
method. When necessary, NMR spectroscopic data were assigned
by using H–H and C–H correlation spectra. Melting points are
uncorrected. MS were recorded with a Hewlett–Packard 5980 GC
and a Hewlett–Packard 5989B MS. IR spectra were recorded with
a Bruker Vektor 22 FTIR spectrometer. TLC was performed on
Merck 60 F254 precoated silica plates and spots were detected by
spraying with a solution of 10% KMnO4 and 0.5  K2CO3 in H2O
and heating. Flash chromatography was performed with silica gel
60 (Merck, 40–63 µm). Petroleum ether (PE) with the boiling range
60–70 °C was used in the separations. All solvents were distilled
before use.
Scheme 6. Reaction of the aluminium salt 3d with dienophiles (only
2H-Spiro[cyclobutabenzene-1,2Ј-[1,3]dithiolan]-2-ol (6): A solution
of benzocyclobutenone 5 (208 mg, 1 mmol) in dry THF (5 mL) was
treated with diisobutylaluminium hydride (1  in hexanes, 1.1 mL,
1.1 mmol) at –5 °C. The reaction was complete after 10 min and
saturated sodium potassium tartrate (10 mL) and Et2O (10 mL)
were added. The resulting mixture was vigorously stirred for
20 min. The aqueous phase was separated and extracted with Et2O
(3ϫ5 mL). The combined organic layers were washed with brine
(10 mL) and dried. Removal of the solvent in vacuo followed by
flash chromatography (PE/EtOAc, 10:1) provided the product as a
one enantiomer is shown; products after work-up).
Particularly interesting is the reaction of aluminium salt
3d and diethyl maleate (18, Scheme 6). The expected naph-
thalene 17e was observed in the crude product, which on
flash chromatography was converted into lactone 19 by
acid-induced transesterification, clearly under the action of
silica gel.
The composition and expected configuration of 19 were
confirmed by an X-ray crystal analysis (Figure 2). A similar
colorless oil (161 mg, 77% yield). IR (film): ν = 3394, 3064, 2923,
˜
1590, 1450, 1420, 1390, 1274, 1174, 1151, 1103, 1059, 913,
1
747 cm–1. H NMR (400 MHz): δ = 7.36 (m, 3 H), 7.26 (m, 1 H),
5.17 (s, 1 H), 3.53 (m, 1 H), 3.40 (m, 2 H), 3.31 (m, 1 H) ppm. 13C
NMR (100 MHz): δ = 145.9 (o), 141.6 (o), 130.7 (+), 130.6 (+),
123.5 (+), 123.1 (+), 84.1 (+), 75.7 (o), 40.1 (–), 39.4 (–) ppm. MS
(CI): m/z = 211, 210, 182, 166, 149, 134. HRMS (EI): calcd. for
C10H10OS2: 210.0173; found 210.0166.
2-(1,3-Dithiolan-2-yl)benzaldehyde (7): On standing at room tem-
perature, product 6 isomerized to phthalaldehyde derivative 7; this
conversion was complete within a few hours. 1H NMR (200 MHz):
δ = 10.09 (s, 1 H), 7.80, 7.58, 7.37, 7.28 (each m, 1 H), 6.46 (s, 1
Figure 2. Crystal structure of 19 (ORTEP plot).
1018
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© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2009, 1016–1021

Highly Substituted 1,4-Dihydronaphthalenes
H), 3.23 (m, 4 H) ppm. 13C NMR (50 MHz): δ = 192.7 (+), 147.7
(o), 142.9 (o), 133.8 (+), 133.75 (+), 130.3 (+), 129.1 (+), 51.22 (+),
39.8 (–) ppm.
1.1 Hz, 1 H), 5.17 (d, J = 3.9 Hz, 1 H), 4.22 (dd, J = 3.9, 5.1 Hz,
1 H), 4.02 (d, J = 5.1 Hz, 1 H), 3.65, 3.49, 3.36, 3.16 (m, 1 H), 0.33
(s, 9 H), –0.07, –0.55 (s, 3 H) ppm. 13C NMR (100 MHz): δ = 197.0
(o), 194.9 (o), 139.0 (o), 138.8 (o), 135.7 (o), 134.5 (o), 134.0 (+),
132.7 (+), 129.6 (+), 129.3 (+), 129.2 (+), 127.5 (+), 127.2 (+), 125.8
(+), 70.0 (+), 67.3 (o), 60.0 (+), 56.1 (+), 43.0 (–), 39.7 (–), 25.3 (+,
3 C), 17.8 (o), –4.5 (+), –4.6 (+) ppm. MS (CI): m/z = 483, 482,
467, 425, 351, 290, 277, 258, 244, 215, 202. HRMS (EI): calcd. for
C26H30O3S2Si: 482.1405; found 482.1397.
tert-Butyldimethylsilyl [6-(1,3-Dithiolan-2-ylidene)cyclohexa-2,4-di-
enylidene]methyl Ether (8): A solution of alcohol 6 (210 mg,
1.0 mmol) in dry CH2Cl2 (4 mL) was treated with Et3N (0.42 mL,
3.0 mmol), 4-DMAP (12 mg, 0.1 mmol) and TBSOTf (0.25 mL,
1.1 mmol) at 0 °C. The reaction was complete after 1 h and satu-
rated NaHCO3 (10 mL) and CH2Cl2 were added. The aqueous
phase was separated and extracted with CH2Cl2 (3ϫ5 mL). The
combined organic layers were washed with brine (10 mL) and
dried. Removal of the solvent in vacuo followed by flash
chromatography (PE/EtOAc, 50:1) provided the product as a yel-
1Ј-{[tert-Butyl(dimethyl)silyl]oxy}-1ЈH,4ЈЈH-dispiro[1,3-dithiolane-
2,4Ј-isochromene-3Ј,1ЈЈ-naphthalen]-4ЈЈ-one (12a): Yield 328 mg
(68%); m.p. 114–117 °C (dec.). IR (film): ν = 2954, 2928, 2885,
˜
2856, 1637, 1598, 1471, 1388, 1360, 1329, 1299, 1253, 1214, 1093,
1
low oil (236 mg, 72% over two steps). IR (film): ν = 2953, 2927,
1028, 1004, 840, 763 cm–1. H NMR (400 MHz): δ = 8.29 (d, J =
˜
2855, 1471, 1459, 1361, 1255, 1205, 1186, 1120, 1080, 882, 837,
8.0 Hz, 1 H), 8.05 (dd, J = 1.0, 7.7 Hz, 1 H), 7.88 (dd, J = 8.0,
1
779, 738 cm–1. H NMR (400 MHz): δ = 7.32 (m, 3 H), 7.16 (m, 1 1.5 Hz, 1 H), 7.57, 7.49 (dt, J = 1.0, 7.8 Hz, 1 H), 7.42 (d, J =
H), 5.43 (s, 1 H), 3.28–3.51 (m, 4 H), 0.99 (s, 9 H), 0.22, 0.21 (each, 10.6 Hz, 1 H), 7.33 (m, 3 H), 6.37 (s, 1 H), 6.32 (d, J = 10.5 Hz, 1
3 H) ppm. 13C NMR (100 MHz): δ = 146.2 (o), 145.1 (o), 130.5
H), 3.19 (dt, J = 4.8, 10.5 Hz, 1 H), 2.93 (dt, J = 11.4, 4.1 Hz, 1
(+), 129.8 (+), 122.8 (+), 122.3 (+), 84.3 (+), 75.4 (o), 40.6 (–), 39.4 H), 2.67 (dt, J = 11.0, 4.1 Hz, 1 H), 1.48 (dt, J = 4.8, 11.4 Hz, 1
(–), 25.9 (+, 3 C), 18.5 (o), –4.3 (+), –4.5 (+) ppm. MS (CI): m/z = H), 0.90 (s, 9 H), 0.24, 0.04 (s, 3 H) ppm. 13C NMR (50 MHz,
325, 324, 267, 256, 239, 207, 165, 149, 133, 121. HRMS (EI): calcd.
for C16H25OS2Si: 324.1037; found 324.1034.
C6D6): δ = 183.7 (o), 146.7 (+), 140.7 (o), 138.5 (o), 137.9 (o), 134.6
(o), 133.9 (+), 131.0 (+), 130.0 (+), 129.6 (+), 129.3 (+), 129.1 (+),
126.8 (+), 126.1 (+), 125.1 (+), 91.8 (+), 77.3 (o), 77.4 (o), 41.8
(–), 40.9 (–), 25.8 (+, 3 C), 18.1 (o), –3.9 (+), –5.3 (+) ppm. MS
(EI): m/z = 483, 425, 324, 239, 165, 149, 73. HRMS (EI): calcd. for
C26H30O3S2Si – tBu: 425.0699; found 425.0701.
Cycloaddition Reactions of Silyl Ether 8 with Alkynes 4 or Naphtho-
quinone 10. General Procedure: A solution of silyl ether 8 (324 mg,
1 mmol) in toluene (4 mL) was treated with the dienophile 4 or 10
(1.1 mmol) at room temp. The reaction was complete after 36–48 h.
The solvent was removed in vacuo and the crude product was puri-
fied by flash chromatography.
Crystal Data of 12a: C26H30O3S2Si (486.68), crystal size
0.30ϫ0.33ϫ0.41 mm. The crystal structure was determined by X-
ray diffraction analysis using graphite-monochromated Mo-Kα ra-
diation (0.71073 Å) [T = 293(2) K]. The scattering intensities were
collected with a single-crystal diffractometer (STOE IPDS II). The
crystal structure was solved by direct methods using SHELXS-97
and refined by using alternating cycles of least-squares refinements
against F2 (SHELXL-97). All non-hydrogen atoms were located in
difference Fourier maps and were refined with anisotropic displace-
ment parameters. The hydrogen positions were determined by a
final difference Fourier synthesis. The compound crystallized or-
thorhombic crystals, space group Pbca, unit cell dimensions: a =
8.608(1), b = 16.130(1), c = 37.242(1) Å, cell volume V =
5170.9(7) Å3, Z = 8, F(000) = 2064 using 5292 independent reflec-
tions and 350 parameters, R1 = 0.0581, wR2 = 0.1497 [IϾ2σ(I)],
goodness of fit on F2 = 1.040, residual electron density: 0.271 and
–0.514 eÅ–3.
Methyl 4Ј-{[tert-Butyl(dimethyl)silyl]oxy}-4ЈH-spiro[1,3-dithiolane-
2,1Ј-naphthalene]-2Ј-carboxylate (9a): Yield 253 mg (62%). IR
(film): ν = 2953, 2929, 2857, 1732, 1652, 1472, 1434, 1361, 1266,
˜
1230, 1199, 1126, 1085, 1050, 1035, 911, 848, 836, 776, 756 cm–1.
1H NMR (400 MHz): δ = 7.99 (d, J = 8.1 Hz, 1 H), 7.40 (d, J =
7.7 Hz, 1 H), 7.34 (t, J = 8.1 Hz, 1 H), 7.26 (m, J = 7.7 Hz, 1 H),
6.85 (d, J = 2.9 Hz, 1 H), 5.30 (d, J = 2.9 Hz, 1 H), 3.91 (m, 2 H),
3.83 (s, 3 H), 3.79 (m, 1 H), 3.67 (m, 1 H), 0.96 (s, 9 H), 0.19 (s, 3
H), 0.11 (s, 3 H) ppm. 13C NMR (100 MHz): δ = 166.4 (o), 140.8
(o), 138.7 (o), 135.2 (o), 135.1 (o), 122.8 (+), 127.9 (+), 127.2 (+),
126.1 (+), 65.2 (+), 62.3 (o), 52.0 (+), 44.3 (–), 43.4 (–), 25.8 (+, 3
C), 18.1 (o), –4.0 (–), –4.3 (–) ppm. MS (CI): m/z = 409, 408, 377,
351, 316, 277, 259, 245, 218, 186, 158. HRMS (EI): calcd. for
C20H28O2S2Si: 408.1249; found 408.1248.
Dimethyl 4Ј-{[tert-Butyl(dimethyl)silyl]oxy}-4Ј-spiro[1,3-dithiolane-
2,1Ј-naphthalene]-2Ј,3Ј-dicarboxylate (9b): Yield 363 mg (78%). IR
CCDC-226514 contains the supplementary crystallographic data
for 12a. These data can be obtained free of charge from The Cam-
bridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
(film): ν = 2954, 2928, 2856, 1728, 1643, 1472, 1434, 1260, 1204,
˜
1139, 1086, 1050, 966, 881, 837, 776, 735 cm–1. 1H NMR
(400 MHz): δ = 7.97 (d, J = 8.0 Hz, 1 H), 7.34 (m, 1 H), 7.25 (m,
2 H), 5.69 (s, 1 H), 3.82 (s, 6 H), 3.71 (m, 2 H), 3.62 (m, 1 H), 3.54
In situ Reduction of Ketone 5 and Cycloaddition Reactions with Al-
(m, 1 H), 0.78 (s, 9 H), 0.08, 0.04 (each s, 3 H) ppm. 13C NMR kynes 4, Quinone 10, or Alkene 14. General Procedure: A solution
(100 MHz): δ = 167.3 (o), 165.8 (o), 148.2 (o), 141.2 (o), 135.3 (o), of ketone 5 (208 mg, 1 mmol) in dry toluene (5 mL) was treated
131.2 (o), 128.5 (+), 128.4 (+), 128.2 (+), 127.4 (+), 65.9 (+), 63.7 with tris(pentafluorophenyl)borane solution (0.77  in toluene,
(o), 52.4 (+), 52.2 (+), 44.2 (–), 42.4 (–), 25.5 (+, 3 C), 17.9 (o), 2 mol-%) and dimethyl(phenyl)silane (1.1 mmol) at room temp. The
–4.3 (+), –4.4 (+) ppm. MS (CI): m/z = 409, 377, 305, 291, 276,
244, 213, 133. HRMS (EI): calcd. for C22H30O5S2Si – tBu:
409.0600; found 409.0600.
reaction was complete after 10 min and the appropriate dienophile
(1.1 mmol) was added. The resulting mixture was stirred at room
temp. for 16–24 h. Saturated NaHCO3 solution (5 mL) was added.
The aqueous phase was separated and extracted with toluene
(3ϫ3 mL). The combined organic layers were washed with brine
(10 mL) and dried with Na2SO4. Removal of the solvent in vacuo
followed by flash chromatography (PE/EtOAc, 10:1) gave the prod-
ucts 9c,d, 11b, 12b, and 15a, respectively.
12Ј-{[tert-Butyl(dimethyl)silyl]oxy}-11aЈ,12Ј-dihydro-5aЈH-spiro-
[1,3-dithiolane-2,5Ј-tetracene]-6Ј,11Ј-dione (11a): Yield 121 mg
(25%). IR (film): ν = 2958, 2927, 2856, 1708, 1688, 1596, 1472,
˜
1327, 1288, 1254, 1215, 1115, 1051, 981, 911, 848, 836, 824, 776,
1
754, 734 cm–1. H NMR (400 MHz): δ = 8.09 (m, 1 H), 8.05 (dd,
J = 8.1, 1.0 Hz, 1 H), 7.89 (m, 1 H), 7.68 (m, 2 H), 7.36 (dt, J = Methyl 4Ј-{[Dimethyl(phenyl)silyl]oxy}-4ЈH-spiro[1,3-dithiolane-
1.3, 7.7 Hz, 1 H), 7.20 (dt, J = 1.1, 7.7 Hz, 1 H), 7.11 (dd, J = 7.7, 2,1Ј-naphthalene]-2Ј-carboxylate (9c): Yield 312 mg (73 %). IR
Eur. J. Org. Chem. 2009, 1016–1021
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K. Benda, W. Regenhardt, E. Schaumann, G. Adiwidjaja
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(film): ν = 3068, 2956, 1733, 1429, 1252, 1120, 1084, 1021, 871, 2 C), 126.5 (+), 111.4 (o), 110.4 (o), 110.3 (o), 108.6 (o), 72.4 (+),
˜
829, 701 cm–1. H NMR (400 MHz): δ = 7.96 (m, 1 H), 7.64 (m, 1 71.5 (o), 53.6 (o), 44.0 (–), 43.1 (o), –0.86 (+), –1.54 (+) ppm. MS
1
H), 7.60 (m, 1 H), 7.40 (m, 4 H), 7.31 (m, 1 H), 7.22 (m, 1 H), 6.75
(d, J = 3.1 Hz, 1 H), 5.32 (d, J = 3.1 Hz, 1 H), 3.91 (m, 2 H), 3.78
(s, 3 H), 3.67 (m, 2 H), –0.27 (s, 3 H), –1.0 (s, 3 H) ppm. 13C NMR
(100 MHz): δ = 166.2 (o), 141.0 (o), 137.9 (+), 137.2 (o), 134.9 (o),
134.4 (o), 133.6 (+), 133.0 (+), 129.9 (+), 128.0 (+), 127.9 (+), 127.3
(+), 126.4 (+), 65.2 (+), 62.2 (o), 51.2 (+), 44.4 (–), 43.6 (–), –0.83
(+), –1.1 (+) ppm. MS (EI): m/z = 428, 393, 367, 335, 307, 290, 262,
233, 202, 135, 107, 91, 51. HRMS (EI): calcd. for C22H24O3S2Si:
428.0936; found 428.0929.
( E S I ) : m / z = 4 9 5 [ M + N a ] + . H R M S ( E I ) : c a l c d . fo r
C24H20N4OS2Si: 472.0848; found 472.0848.
Cycloaddition Reactions of Alkoxide 3d. General Procedure: A solu-
tion of ketone 5 (208 mg, 1 mmol) in dry THF (5 mL) was treated
with diisobutylaluminium hydride (1  in hexanes, 1.1 mL,
1.1 mmol) at –5 °C. The reaction was complete after 10 min and
dienophile 4, 14, 16 or 18 (1.1 mmol) was added. The resulting
mixture was warmed to room temp. and stirred for 10 h. Saturated
sodium potassium tartrate (10 mL) and Et2O (10 mL) were added
and the mixture was vigorously stirred for 20 min. The aqueous
phase was separated and extracted with Et2O (3ϫ5 mL). The com-
bined organic layers were washed with brine (10 mL) and dried.
Removal of the solvent in vacuo followed by flash chromatography
(PE/EtOAc, 2:1) gave products 2a,b, 15b, 17a–d, or 19.
Dimethyl 4Ј-{[Dimethyl(phenyl)silyl]oxy}-4ЈH-spiro[1,3-dithiolane-
2,1Ј-naphthalene]-2Ј,3Ј-dicarboxylate (9d): Yield 194 mg (40 %);
m.p. 107–108 °C. IR (film): ν = 3070, 2949, 1722, 1427, 1368, 1263,
˜
1119, 1016, 962, 889, 831, 701 cm–1. 1H NMR (400 MHz): δ = 7.97
(dd, J = 8.0, 1.2 Hz, 1 H), 7.54 (m, 2 H), 7.35 (m, 4 H), 7.17 (dt,
J = 7.6, 1.2 Hz, 1 H), 7.04 (dd, J = 7.6, 1.4 Hz, 1 H), 5.75 (s, 1 H),
3.83 (s, 3 H), 3.71 (m, 2 H), 3.64 (s, 3 H), 3.59 (m, 2 H), 0.36 (s, 3
H), 0.35 (s, 3 H) ppm. 13C NMR (100 MHz): δ = 167.1 (o), 165.5
(o), 147.9 (o), 140.9 (o), 138.0 (o), 134.8 (o), 133.5 (+), 131.0 (o),
129.4 (+), 128.4 (+), 128.3 (+), 128.2 (+), 127.6 (+), 127.4 (+), 65.8
(+), 63.5 (o), 52.2 (+), 52.1 (+), 44.0 (–), 42.4 (–), –0.28 (+), –1.1
(+) ppm. MS (EI): m/z = 486, 471, 458, 408, 398, 367, 348, 334,
316, 262, 233, 195, 135, 107, 61. HRMS (EI): calcd. for
C24H26O5S2Si: 486.0991; found 486.0990.
Methyl 4Ј-Hydroxy-4ЈH-spiro[1,3-dithiolane-2,1Ј-naphthalene]-3Ј-
carboxylate (2a): Yield 188 mg (64%); m.p. 101–102 °C. IR (film):
ν = 3485, 2950, 2922, 1710, 1650, 1484, 1437, 1278, 1250, 1220,
˜
1
1126, 1027, 1007, 965, 911, 762, 733 cm–1. H NMR (400 MHz): δ
= 7.97 (d, J = 7.7 Hz, 1 H), 7.55 (d, J = 7.4 Hz, 1 H), 7.34 (m, 2
H), 7.20 (s, 1 H), 5.49 (s, 1 H), 3.87 (s, 3 H), 3.73 (m, 2 H), 3.63
(m, 2 H), 3.47 (br. s, 1 H) ppm. 13C NMR (100 MHz): δ = 167.6
(o), 142.1 (+), 135.3 (o), 135.1 (o), 130.0 (+), 128.6 (+), 128.4 (+),
128.3 (+), 123.6 (o), 63.0 (+), 62.6 (o), 52.2 (+), 42.1 (–), 41.9 (–
) ppm. MS (CI): m/z = 294, 276, 245, 219, 187, 145, 128. HRMS
(EI): calcd. for C14H14O3S2: 294.0384; found 294.0388.
12Ј-{[Dimethyl(phenyl)silyl]oxy}-11aЈ,12Ј-dihydro-5ЈaH-spiro[1,3-di-
thiolane-2,5Ј-tetracene]-6Ј,11Ј-dione (11b): Yield 108 mg (22%). IR
(film): ν = 3068, 2958, 1771, 1694, 1595, 1427, 1255, 1118, 1051,
˜
1
982, 832 cm–1. H NMR (400 MHz): δ = 8.11 (m, 1 H), 8.01 (dd,
Dimethyl 4Ј-Hydroxy-4ЈH-spiro[1,3-dithiolane-2,1Ј-naphthalene]-
2Ј,3Ј-dicarboxylate (2b): Yield 264 mg (75%); m.p. 135–136 °C. IR
J = 8.0, 1.0 Hz, 1 H), 7.87 (m, 1 H), 7.63 (m, 2 H), 7.25 (m, 4 H),
7.16 (dd, J = 8.0, 1.0 Hz, 2 H), 6.95 (dt, J = 7.5, 1.2 Hz, 1 H), 6.60
(d, J = 7.5 Hz, 1 H), 5.11 (d, J = 3.5 Hz, 1 H), 4.18 (dd, J = 5.0,
3.5 Hz, 1 H), 4.02 (d, J = 5.0 Hz, 1 H), 3.65, 3.48, 3.34, 3.16 (m, 1
H), –0.23, –0.31 (s, 3 H) ppm. 13C NMR (100 MHz): δ = 197.0 (o),
195.1 (o), 139.1 (o), 138.8 (o), 136.6 (o), 135.6 (o), 134.0 (+), 133.8
(o), 133.4 (+), 132.7 (+), 129.7 (+), 129.5 (+), 129.3 (+), 129.0 (+),
127.8 (+), 127.7 (+), 127.4 (+), 126.5 (+), 125.6 (+), 70.1 (+), 67.3
(o), 59.9 (+), 56.3 (+), 42.9 (–), 39.6 (–), –2.1 (+), –2.3 (+) ppm.
HRMS (EI): calcd. for C28H26O3S2Si: 502.1093; found 502.1095.
(film): ν = 3483, 2951, 1726, 1639, 1485, 1435, 1266, 1206, 1144,
˜
1
1086, 922, 961, 912, 732 cm–1. H NMR (400 MHz): δ = 7.94 (m,
1 H), 7.46 (m, 1 H), 7.34 (m, 2 H), 5.60 (s, 1 H), 3.86, 3.84 (each
s, 3 H), 3.69 (m, 4 H), 2.79 (br. s, 1 H) ppm. 13C NMR (100 MHz):
δ = 167.1 (o), 165.7 (o), 147.5 (o), 139.6 (o), 133.7 (o), 129.6 (o),
128.8 (+), 128.4 (+, 2 C), 128.1 (+), 64.6 (+), 63.6 (o), 52.8 (+),
52.4 (+), 43.9 (–), 42.8 (–) ppm. MS (EI): m/z = 352, 320, 292, 260,
233, 145, 59. HRMS (EI): calcd. for C16H16O5S2: 352.0440; found
352.0439.
4Ј-Hydroxy-2ЈH-spiro[1,3-dithiolane-2,1Ј-naphthalene]-2Ј,2Ј,3Ј,3Ј
(4ЈH)-tetracarbonitrile (15b): Yield 162 mg (48%); m.p. 142–144 °C.
1Ј-{[Dimethyl(phenyl)silyl]oxy}-1ЈH,4ЈЈH-dispiro[1,3-dithiolane-
2,4Ј-isochromene-3Ј,1ЈЈ-naphthalen]-4ЈЈ-one (12b): Yield 187 mg
IR (KBr): ν = 3280, 2917, 2849, 1707, 1483, 1455, 1422, 1374, 1316,
˜
(38%); m.p. 145–146 °C. IR (film): ν = 2917, 1673, 1597, 1429,
˜
1246, 1207, 1144, 1045, 980, 893, 770, 744, 730 cm–1. 1H NMR
(200 MHz): δ = 7.93 (d, J = 7.6 Hz, 1 H), 7.61 (dt, J = 1.5, 7.4 Hz,
1 H), 7.43 (dt, J = 7.6, 1.5 Hz, 1 H), 7.21 (d, J = 7.4 Hz, 1 H), 5.31
(s, 1 H), 3.84 (m, 4 H) ppm. 13C NMR (50 MHz): δ = 137.6 (o),
137.5 (o), 132.8 (+), 132.5 (+), 129.8 (+), 127.5 (+), 110.4 (o), 110.3
(o), 108.7 (o), 108.6 (o), 80.5 (o), 80.1 (o), 60.4 (o), 53.5 (+), 43.8
(–), 43.2 (–) ppm. MS (EI): m/z = 338, 310, 267, 235, 209, 181, 164,
149, 121. HRMS (EI): calcd. for C16H10N4OS2: 338.0296; found
338.0297.
1
1387, 1347, 1254, 1211, 1118, 1020, 957, 834, 699 cm–1. H NMR
(400 MHz): δ = 8.32 (dd, J = 0.9, 7.9 Hz, 1 H), 8.10 (dd, J = 1.0,
7.7 Hz, 1 H), 7.91 (m, 1 H), 7.60 (m, 3 H), 7.49 (dt, J = 1.0, 7.7 Hz,
1 H), 7.38 (d, J = 10.6 Hz, 1 H), 7.37 (m, 4 H), 7.28 (m, 2 H), 6.42
(s, 1 H), 6.25 (d, J = 10.6 Hz, 1 H), 3.21 (m, 1 H), 2.93 (m, 1 H),
2.67 (m, 1 H), 1.48 (m, 1 H), 0.51, 0.50 (each s, 3 H) ppm. 13C
NMR (100 MHz): δ = 184.7 (o), 146.8 (+), 140.3 (o), 137.6 (o),
136.7 (o), 133.7 (+), 133.6 (o), 133.3 (o), 130.3 (+), 129.8 (+), 129.0
(+), 129.0 (+), 128.8 (+), 128.0 (+), 127.9 (+), 127.7 (+), 126.6 (+),
124.6 (+), 91.4 (+), 77.1 (o), 76.8 (o), 41.9 (–), 40.9 (–), –1.3 (+),
–1.4 (+) ppm. MS (ESI): m/z = 525 [M + Na]+. HRMS (EI): calcd.
for C28H26O3S2Si: 502.1093; found 502.1094.
Dimethyl (2ЈS*,3ЈR*)-4Ј-Hydroxy-3Ј,4Ј-dihydro-2ЈH-spiro[1,3-di-
thiolane-2,1Ј-naphthalene]-2Ј,3Ј-dicarboxylate (17a): Yield 242 mg
(68%); m.p. 126–128 °C. IR (KBr): ν = 3466, 2954, 1784, 1741,
˜
4Ј-{[Dimethyl(phenyl)silyl]oxy}-2ЈH-spiro[1,3-dithiolane-2,1Ј-naph- 1484, 1437, 1364, 1286, 1200, 1059, 960, 855, 771, 683 cm–1. 1H
thalene]-2Ј,2Ј,3Ј,3Ј(4H)-tetracarbonitrile (15a): Yield 297 mg (63%). NMR (200 MHz): δ = 7.92 (d, J = 7.6 Hz, 1 H), 7.32 (m, 3 H),
IR (film): ν = 3072, 2961, 2273, 1774, 1481, 1428, 1259, 1209, 1117,
5.06 (d, J = 3.8 Hz, 1 H), 3.89 (d, J = 10.7 Hz, 1 H), 3.77, 3.76
(each s, 3 H), 3.61 (dd, J = 10.7, 3.8 Hz, 1 H), 3.48 (m, 4 H) ppm.
13C NMR (50 MHz): δ = 172.1 (o), 171.9 (o), 140.2 (o), 134.9 (o),
130.3 (+), 129.1 (+), 128.4 (+), 128.3 (+), 68.6 (o), 67.5 (+), 52.3
(+), 52.1 (+), 50.5 (+), 49.2 (+), 42.1 (–), 41.7 (–) ppm. MS (EI):
m/z = 354, 322, 294, 276, 262, 250, 234, 217, 202, 186, 149, 115,
˜
1
911, 826, 738 cm–1. H NMR (400 MHz): δ = 7.70 (d, J = 8.0 Hz,
1 H), 7.67 (m, 2 H), 7.46 (m, 4 H), 7.30 (m, 1 H), 7.13 (d, J =
8.0 Hz, 1 H), 5.49 (s, 1 H), 3.81 (m, 4 H), 0.74 (s, 3 H), 0.67 (s, 3
H) ppm. 13C NMR (100 MHz): δ = 134.1 (o), 133.9 (o), 133.8 (+,
2 C), 131.1 (+), 130.9 (+), 130.8 (o), 130.2 (+), 129.9 (+), 128.4 (+,
1020
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© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2009, 1016–1021

Highly Substituted 1,4-Dihydronaphthalenes
77. C16H18O5S2: C 54.22, H 5.12, S 18.09; found C 54.35, H 5.02,
S 18.63.
128, 115, 89, 71, 51. HRMS (EI): calcd. for C16H16O4S2: 336.0490;
found 336.0491.
Crystal Data for 19: C16H16O4S2 (336.41), crystal size
0.33ϫ0.28ϫ0.21 mm. The crystal structure was solved as de-
scribed above for 12a. The crystal of the compound was triclinic,
Methyl (3ЈR*,4ЈR*)-4-Hydroxy-3Ј,4Ј-dihydro-2ЈH-spiro[1,3-dithio-
lane-2,1Ј-naphthalene]-3Ј-carboxylate (17b): Yield 149 mg (50%);
m.p. 135–136 °C. IR (KBr): ν = 3494, 2924, 1720, 1445, 1393, 1378,
˜
¯
space group P1, unit cell dimensions: a = 8.317(1), b = 10.068(1),
1302, 1290, 1277, 1243, 1226, 1198, 1165, 1126, 1105, 1052, 974,
c = 10.761(1) Å, α = 70.15(1), β = 74.34(1), γ = 68.52(1)°, Z = 2, cell
volume V = 777.69(14) Å3, F(000) = 352 using 3549 independent
reflections and 228 parameters, R1 = 0.0540, wR2 = 0.1457
[IϾ2σ(I)], goodness of fit on F2 = 1.155, residual electron density:
0.558 and –0.586 eÅ–3.
1
931, 746, 496 cm–1. H NMR (200 MHz): δ = 7.96 (d, J = 7.3 Hz,
1 H), 7.29 (m, 3 H), 5.04 (d, J = 2.4 Hz, 1 H), 3.78 (s, 3 H), 3.48
(m, 4 H), 3.21 (dt, J = 2.6, 12.5 Hz, 1 H), 2.83 (d, J = 12.5 Hz, 2
H) ppm. 13C NMR (50 MHz): δ = 173.6 (o), 138.2 (o), 136.1 (o),
130.5 (+), 129.7 (+), 128.8 (+), 128.2 (+), 67.9 (o), 67.0 (+), 52.1
(+), 45.3 (+), 41.3 (–), 40.3 (–), 38.6 (–) ppm. MS (EI): m/z = 296,
278, 232, 218, 187, 173, 159, 115, 75. C14H16O3S2: C 56.73, H 5.44,
S 21.64; found C 56.63, H 5.48, S 21.30.
Acknowledgments
We thank the German Fonds der Chemischen Industrie (Frankfurt/
Main) for financial support. A scholarship from the “Graduiert-
enförderung des Landes Niedersachsen” for K. B. is gratefully ac-
knowledged.
Methyl (2ЈR*,3ЈR*,4R*)-4Ј-Hydroxy-2Ј-phenyl-3Ј,4Ј-dihydro-2ЈH-
spiro[1,3-dithiolane-2,1Ј-naphthalene]-3Ј-carboxylate (17c): Yield
252 mg (68%); m.p. 134–136 °C. IR (film): ν = 3449, 3030, 1735,
˜
1
1600, 1494, 1450, 1376, 1238, 1027, 969, 750, 700 cm–1. H NMR
(200 MHz): δ = 8.04 (d, J = 7.3 Hz, 1 H), 7.58 (m, 3 H), 7.30 (m,
5 H), 5.00 (d, J = 2.8 Hz, 1 H), 4.21 (d, J = 11.8 Hz, 1 H), 3.66
(dd, J = 2.8, 11.8 Hz, 1 H), 3.49 (s, 3 H), 3.30 (m, 2 H), 3.09, 2.72
(each m, 1 H) ppm. 13C NMR (50 MHz): δ = 173.5 (o), 140.5 (o),
138.1 (o), 136.6 (o), 128.9 (+), 128.7 (+), 128.5 (+), 128.4 (+), 127.9
(+), 127.6 (+), 127.1 (+), 127.0 (+), 126.4 (+), 72.8 (o), 68.0 (+),
51.8 (+), 50.3 (+), 49.9 (+), 41.8 (–), 41.6 (–) ppm. MS (EI): m/z
= 372, 355, 326, 296, 279, 263, 234, 210, 182, 149, 121, 105, 92.
C20H20O3S2: C 64.49, H 5.41, S 17.22; found C 63.87, H 5.39, S
17.70.
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Am. Chem. Soc. 2005, 127, 15028–15029.
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2889; b) J. L. Segura, N. Martín, Chem. Rev. 1999, 99, 3199–
3246.
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J. Am. Chem. Soc. 2000, 122, 571–575; d) S. J. Shaw, Synth.
Commun. 2007, 37, 4183–4189.
Ethyl (2ЈR*,3ЈR*,4ЈR*)-2Ј-Cyano-4Ј-hydroxy-3Ј,4Ј-dihydro-2ЈH-
spiro[1,3-dithiolane-2,1Ј-naphthalene]-3Ј-carboxylate (17d): Yield
224 mg (67%); m.p. 68 °C. IR (KBr): ν = 3458, 2979, 2927, 2248,
˜
1733, 1447, 1372, 1296, 1212, 1131, 1042, 755 cm–1 1H NMR
.
[5] S. Winter-Extra, G. Rühter, E. Schaumann, J. Org. Chem. 1990,
55, 4200–4202.
(200 MHz): δ = 8.01 (dd, J = 7.5, 1.7 Hz, 1 H), 7.44 (dd, J = 7.3,
1.9 Hz, 1 H); 7.37 (m, 2 H), 5.21 (d, J = 4.2 Hz, 1 H), 4.37 (d, J =
7.2 Hz, 2 H), 3.67 (m, 4 H), 3.58 (m, 1 H), 3.37 (m, 1 H), 1.38 (t,
J = 7.2 Hz, 3 H) ppm. 13C NMR (50 MHz): δ = 169.7 (o), 135.3
(o), 134.6 (o), 130.3 (+), 129.8 (+), 129.5 (+), 129.2 (+), 119.3 (o),
69.5 (o), 66.3 (+), 62.0 (–), 47.4 (+), 41.7 (–), 41.3 (–), 41.2 (+),
14.2 (+) ppm. MS (EI): m/z = 334, 317, 307, 289, 241, 210, 182,
169, 149, 121, 77, 51. HRMS (EI): calcd. for C16H17NO3S2:
335.0650; found 335.0647.
[6] Conference Report: E. Schaumann, K. Benda, Phosphorus Sul-
fur Silicon Relat. Elem. 2005, 180, 1463–1464.
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[15] W. Regenhardt, E. Schaumann, H. W. Moore, Synthesis 2001,
1076–1080.
Ethyl (1ЈR*,4ЈR*,10ЈR*)-3Ј-Oxo-3Ј,4Ј-dihydro-1ЈH-spiro[1,3-dithiol-
ane-2,5Ј-[1,4]methano[2]benzoxepine]-10Ј-carboxylate (19): Yield
84 mg (25%); m.p. Ͼ185 °C (dec.). IR (film): ν = 3123, 1776, 1728,
˜
1377, 1333, 1269, 1170, 1143, 1053, 948, 917, 887, 604 cm–1. 1H
NMR (400 MHz): δ = 7.94 (d, J = 7.9 Hz, 1 H), 7.42 (dt, J = 7.0,
1.8 Hz, 1 H), 7.22 (m, 2 H), 5.50 (d, J = 1.3 Hz, 1 H), 4.27 (q, J =
7.2 Hz, 2 H), 3.72 (m, 5 H), 5.54 (dd, J = 2.0, 1.3 Hz, 1 H), 1.33
(t, J = 7.2 Hz, 3 H) ppm. 13C NMR (100 MHz): δ = 171.7 (o),
169.3 (o), 136.5 (o), 135.1 (o), 132.0 (+), 130.7 (+), 128.5 (+), 126.9
(+), 79.6 (+), 68.4 (o), 62.2 (–), 54.9 (+), 53.8 (+), 42.4 (–), 40.8
(–), 14.1 (+) ppm. MS (EI): m/z = 336, 308, 263, 247, 233, 191, 160,
Received: November 7, 2008
Published Online: January 16, 2009
Eur. J. Org. Chem. 2009, 1016–1021
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
1021