Tandem 1,3-dipolar cycloaddition of mesoionic 2,4-diphenyl-1,3- oxathiolium-5-olate with cycloocta-1,5-diene. A new synthesis of the tetracyclo[6.2.0.04,10.05,9]decane ring system

Article abstract of DOI:10.1016/S0040-4039(00)00042-3

The mesoionic heterocycle 2,4-diphenyl-1,3-oxathiolium-5-olate (5) undergoes a tandem 1,3-dipolar cycloaddition reaction with cycloocta-1,5- diene (6) to give cycloadduct sulfide 7 in modest yield. Oxidation to sulfone 8 and photochemical extrusion of SO₂ affords 9,10- diphenyltetracyclo[6.2.0.0^4,10.0^5,9]decane (9) in high yield. (C) 2000 Elsevier Science Ltd.

Full text of DOI:10.1016/S0040-4039(00)00042-3

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 41 (2000) 1687–1690
Tandem 1,3-dipolar cycloaddition of mesoionic 2,4-diphenyl-
1,3-oxathiolium-5-olate with cycloocta-1,5-diene. A new
synthesis of the tetracyclo[6.2.0.04,10.05,9]decane ring system
William R. Sponholtz III,† Hernando A. Trujillo ‡ and Gordon W. Gribble ∗
Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, USA
Received 6 December 1999; accepted 29 December 1999
Abstract
The mesoionic heterocycle 2,4-diphenyl-1,3-oxathiolium-5-olate (5) undergoes a tandem 1,3-dipolar cycloaddi-
tion reaction with cycloocta-1,5-diene (6) to give cycloadduct sulfide 7 in modest yield. Oxidation to sulfone 8 and
photochemical extrusion of SO2 affords 9,10-diphenyltetracyclo[6.2.0.04,10.05,9]decane (9) in high yield. © 2000
Elsevier Science Ltd. All rights reserved.
Keywords: 1,3-oxathiolium-5-olate; mesoionic; 1,3-dipolar cycloaddition; tetracyclo[6.2.0.04,10.05,9]decane.
1,3-Dipolar cycloaddition reactions of mesoionic heterocycles, such as sydnones 1 (1,2,3-
oxadiazolium-5-olates), münchnones 2 (1,3-oxazolium-5-olates), isomünchnones 3 (1,3-oxazolium-4-
olates), thioisomünchnones 4 (1,3-thiazolium-4-olates) and related conjugated heterocyclic mesomeric
betaines,1 have seen a resurgence of applications to synthesis.2,3
In continuation of our interest in 1,3-dipolar cycloaddition reactions of sydnones and münchnones with
cyclic dienes4 and nitro-substituted heterocycles,5 we now report that 2,4-diphenyl-1,3-oxathiolium-5-
olate (5), a mesoionic heterocycle that has been neglected since its original generation and trapping
(with dimethyl acetylenedicarboxylate),6 undergoes a tandem 1,3-dipolar cycloaddition reaction with
cycloocta-1,5-diene (6) to afford 9,11-diphenyl-10-thiatetracyclo[6.3.0.04,11.05,9]undecane (7) in 32%
∗
Corresponding author. Tel: 1-603-646-3118; fax: 1-603-646-3946; e-mail: grib@dartmouth.edu (G. W. Gribble)
Permanent address: Department of Sciences, Cushing Academy, Ashburnham, MA 01430, USA.
Permanent address: Department of Chemistry, Albright College, Reading, PA 19612, USA.
†
‡
0040-4039/00/$ - see front matter © 2000 Elsevier Science Ltd. All rights reserved.
PII: S0040-4039(00)00042-3
tetl 16322

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yield after column chromatography (Scheme 1). Mesoionic 5 was generated in situ from S-benzoyl-α-
phenylthioglycolic acid6 and diisopropylcarbodiimide (DIPC), conditions that we have used previously
to generate münchnones.4b,5 Cycloadduct 7 was fully characterized.7,8
Scheme 1.
The facile photochemical elimination of sulfur dioxide from benzylic sulfones9 suggested to
us that the sulfone 8 derived from 7 might undergo a similar extrusion of SO2 to form 9,10-
diphenyltetracyclo[6.2.0.04,10.05,9]decane (9). Indeed, as shown in Scheme 2 this sequence has been
realized. Treatment of sulfide 7 with m-chloroperbenzoic acid (m-CPBA)10 gave sulfone 8 in 94%
yield.11 After some experimentation12 it was found that photolysis of sulfone 8 in 1:1 benzene–acetone
(350 W Hanovia medium pressure lamp, pyrex filter, 2 h) gave the desired hydrocarbon 9 (mp
105–105.5°C) in 95% yield.13 The identity of 9 was confirmed by comparison with a known sample,
prepared by photolysis of 6 and diphenylacetylene to give 9 (mp 105–106°C) in 48% yield.14 The two
samples were identical by IR and 1H and 13C NMR spectroscopy.
Scheme 2.
Along the lines of our previous work involving the 1,3-dipolar cycloaddition reaction of münchnones
with cyclooctatetraene (COT),4b we are currently examining the reaction of COT with 1,3-oxathiolium-
5-olate 5 as a route to the pentaprismane ring system. Also, efforts to extend this chemistry to additional
reactions of 1,3-oxathiolium-5-olates and other mesoionic heterocycles are in progress.
In conclusion, we have shown that the mesoionic heterocycle 2,4-diphenyl-1,3-oxathiolium-5-olate (5)
undergoes a tandem 1,3-dipolar cycloaddition reaction with cycloocta-1,5-diene to form cycloadduct 7.
This sulfide is easily transformed by oxidation and photochemical extrusion of SO2 to caged hydrocarbon
9 in high yield.
Acknowledgements
This work was supported by the Donors of the Petroleum Research Fund (PRF), administered by
the American Chemical Society, Pfizer, Wyeth-Ayerst, and in part by the National Institutes of Health

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(GM58601). We thank Professors David Lemal and David Glueck of this Department for their assistance
with the photolysis experiments and useful discussions, and Professor Michael Walters for the use of
his laboratory. G.W.G. thanks Professor Phil Crews and his colleagues and students at the University
of California, Santa Cruz, for their hospitality during a sabbatical leave between 1999–2000 when this
manuscript was written.
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7. Compound 7: Mp 171–171.5°C; 1H NMR (CD2Cl2) δ 7.6 (m, 4H), 7.35 (m, 4H), 7.25 (m, 2H), 3.0 (bs, 4H), 1.8–1.6 (m,
8H); 13C NMR (CDCl3) δ 139.1, 128.5, 127.3, 127.1, 72.6, 52.3, 24.2; MS m/z 318 (M+), 285, 249, 236, 182 (100%), 171,
141, 115, 91, 77; HRMS m/z calcd for C22H22S (M+) 318.1442, found 318.1436. Anal. calcd for C22H22S: C, 82.97; H, 6.96;
S, 10.07. Found: C, 82.74; H, 7.02; S, 10.16.
8. Although an X-ray crystal structure determination indicated the correctness of 7, the crystals were insidiously twinned and
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(m, 4H), 7.45 (m, 6H), 3.40 (bs, 4H), 2.14 (bd, J=9.3 Hz, 4H), 1.67 (bd, J=10 Hz, 4H); 13C NMR (CDCl3) δ 129.3, 128.9,
128.7, 127.8, 72.2, 43.9, 22.9; uv (EtOH) λmax (ε) 288 (15,000), 256 (530), 262 (590), 263 (510) nm; MS m/z 350, 286,
229, 215, 178, 165, 143 (100%), 128, 77; HRMS m/z calcd for C22H22SO2 (M+) 350.1341, found 350.1345. Anal. calcd for
C22H22O2S: C, 75.40; H, 6.33; S, 9.15. Found: C, 75.12; H, 6.28; S, 8.88.

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12. For example, photolysis of 8 in neat benzene, neat acetone, or 4:1 benzene–acetone gave lower yields of 9, or failed all
together (benzene). Sensitizers with smaller triplet state energies than acetone (i.e., acridine, fluorenone, benzophenone, and
xanthone) failed to extrude SO2 from 8 when photolyzed in benzene solution.
1
13. Compound 9: Mp 105–105.5°C (lit.14 mp 105.5–106.5°C); H NMR (CDCl3) δ 7.22 (tt, J=1.5 and 7.6 Hz, 4H), 7.1 (tt,
J=1.2 and 7.3 Hz, 2H), 7.02 (dt, J=1 and 7.6 Hz, 4H), 3.1 (bd, J=3 Hz, 4H), 2.1 (d, J=9 Hz, 4H), 1.8 (bd, J=9 Hz, 4H); 13
NMR (CDCl3) δ 142.7, 128.1, 126.7, 125.6, 61.3, 44.8, 27.3.
C
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