New bridges in [2.2]paracyclophanes: The interaction of chalcogenide halides with pseudo-geminal triple bonds

Article abstract of DOI:10.1080/10426507.2010.524177

Novel heteroatom containing bridges have been introduced in [2.2]paracyclophanes by the interaction of chalcogenide halides with pseudo-geminal triple bonds. The anti-addition with Markovnikov orientation of selenium halides to 4,15-bisethynyl[2.2]paracyclophane leads to the corresponding E-adducts. The interaction of pseudo-geminally substituted bispropargylic alcohols with disulfur dichloride and sulfur dichloride leads to a mixture of cyclic ethers. These compounds are formed under mild acidic conditions provided by the organic ammonium chlorides or silica gel. The corresponding dipropargyloxy sulfides have been identified as reaction intermediates. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/10426507.2010.524177

Phosphorus, Sulfur, and Silicon, 186:1246–1250, 2011
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426507.2010.524177
NEW BRIDGES IN [2.2]PARACYCLOPHANES:
THE INTERACTION OF CHALCOGENIDE HALIDES
WITH PSEUDO-GEMINAL TRIPLE BONDS
Laura G. Sarbu,1 Aurora Birsa,1 Henning Hopf,2
and Lucian M. Birsa1,2
1Department of Organic Chemistry, Al. I. Cuza University, Iasi, Romania
2Institute of Organic Chemistry, Technical University Braunschweig,
Braunschweig, Germany
Abstract Novel heteroatom containing bridges have been introduced in [2.2]paracyclophanes
by the interaction of chalcogenide halides with pseudo-geminal triple bonds. The anti-addition
with Markovnikov orientation of selenium halides to 4,15-bisethynyl[2.2]paracyclophane leads
to the corresponding E-adducts. The interaction of pseudo-geminally substituted bispropar-
gylic alcohols with disulfur dichloride and sulfur dichloride leads to a mixture of cyclic ethers.
These compounds are formed under mild acidic conditions provided by the organic ammo-
nium chlorides or silica gel. The corresponding dipropargyloxy sulfides have been identified
as reaction intermediates.
Supplemental materials are available for this article. Go to the publisher’s online edition of
Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.
Keywords [2.2]Paracyclophanes; selenium electrophiles; sulfur electrophiles
INTRODUCTION
The sigmatropic rearrangements of allylic and propargylic esters of sulfur acids at
various oxidation states have proven to be a rich source of synthetically valuable and mecha-
nistically intriguing reactions, often yielding novel and surprising products.1,2 However, due
to the rigid molecular framework provided by the paracyclophane unit and its short inter-
annular distance, functional groups in pseudo-geminally substituted [2.2]paracyclophanes
are often held in such a position as to allow highly specific reactions to take place between
them. In one such application, unsaturated cyclophane bisesters undergo intramolecular
photocyclization to the corresponding ladderane isomers.3–5 In view of our past experience
with the use of electrophilic sulfur reagents with hydroxyalkynes,6 we decided to investigate
the reactivity of the chalchogenide halides towards 4,15-bisethynyl[2.2]paracyclophane and
pseudo-geminally substituted propargylic alcohols.
Received 27 June 2010; accepted 13 September 2010.
This work was supported by CNCSIS–UEFISCSU, project number PNII–IDEI 2095/2008.
Address correspondence to Lucian M. Birsa, Institute of Organic Chemistry, Technical University Braun-
schweig, Hagenring 30, Braunschweig, D-38106, Germany. E-mail: lbirsa@uaic.ro
1246

NEW BRIDGES IN [2.2]PARACYCLOPHANES
1247
RESULTS
Preliminary investigations have shown that the reaction of pseudo-geminal bis-
ethynyl[2.2]paracyclophane 1 with n-BuLi in THF followed by treatment with SCl2 re-
sulted in the formation of thiophene substituted paracyclophane derivative 3 (Scheme 1).7
Most likely the cycloaromatization is induced by a nucleophilic attack of THF-anion on
one of the acetylenic carbon atoms of the intermediate unstable sulfide 2.
Scheme 1
Under the same reaction conditions, the treatment of bisacetylene 1 with monosulfur
monochloride leads to the corresponding disulfide 4, in 65% isolated yield (Scheme 2).
The stability of this compound could be explained by a less hindered structure—that of the
monosulfide 2—and the lack of cycloaromatization.
Scheme 2
Prompted by the simple and efficient recent preparation of selenium dichloride from
elemental selenium and sulfuryl chloride,8 we have investigated the reaction of in situ
prepared SeCl2 with pseudo-geminal bis-ethynyl[2.2]paracyclophane 1 (Scheme 3, n =
1). Molecular modeling and preliminary analytical data have indicated that anti-addition
with Markovnikov orientation takes place. The addition of monoselenium monochloride
proceeds in a similar manner (Scheme 3, n = 2), leading to diselenide 5b. In both cases,
the addition of electrophilic selenium reagents to bis-ethynyl[2.2]paracyclophane produced
preferably the corresponding E-adducts.
Scheme 3

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L. G. SARBU ET AL.
The interactions between pseudo-geminally substituted bispropargylic alcohols 6 and
sulfur chlorides have been studied under various experimental conditions. The dipropar-
gyloxy disulfides 7 have been demonstrated as reaction intermediates of monosulfur
monochloride. Under mild acidic conditions provided by Et3N·HCl or silica, these com-
pounds undergo sulfur elimination, providing a mixture of meso-8 and d,l-9 cyclic ethers
in a 2.5:1 ratio (Scheme 4).
Scheme 4 Conditions: (i) S2Cl2, NEt3 (2 eq.), Et2O, –78◦C; (ii) silica gel.
The sulfur dichloride has provided dipropargyloxy sulfides, compounds that were
found to be responsible for a vinylogous pinacol rearrangement (Scheme 5).
Scheme 5 Conditions: (i) SCl2, NEt3 (2 eq.), CH2Cl2, –78◦C; (ii) silica gel.

NEW BRIDGES IN [2.2]PARACYCLOPHANES
1249
The regio- and stereospecific addition of monoselenium monochloride to pseudo-
geminally substituted bispropargylic alcohols was performed under high dilution condi-
tions. The disproportionation reaction of selenium monochloride to selenium dichloride
and triselenium dichloride leads to the corresponding divinylic mono- and triselenides
(Scheme 6). The stereochemistry of the newly generated double bond was assigned as Z by
2D NMR experiments.9 The syn addition of selenium electrophiles appears to be directed
by hydroxyl groups.
Scheme 6
EXPERIMENTAL
Disulfur dichloride and diselenium dichloride was purchased from commercial
sources. Sulfur dichloride was prepared according to data in the literature10 and distilled
prior to use in the presence of phosphorus trichloride. Analytical data are presented in the
Supplemental Materials (available online).
Reaction of Disulfur Dichloride with Bisacetylene 1
To a solution of bisacetylene 1 (128 mg, 0.5 mmol) and tetramethylethylenediamine
(0.15 mL, 1 mmol) in anhydrous THF (100 mL), a solution of n-BuLi (1.6 M, 0.65 mL,
1.05 mmol) was added dropwise at –20◦C. The reaction mixture was stirred at this tempera-
ture for 30 min, and then S2Cl2 (0.04 mL, 0.5 mmol) in anhydrous THF (50 mL) was added
dropwise. After 2 h at this temperature, the mixture was poured into water and extracted
with methylene chloride. After the usual workup, evaporation of the solvent gave the crude
product as brown viscous oil. Purification by column chromatography on silica gel using
CH2Cl2/pentane 1:1 as eluent provided disulfide 4 (100 mg) in 65% isolated yield.
Reaction of Selenium Halides with Bisacetylene 1 and Bispropargylic
Alcohols 6: Typical Procedure
To a solution of bisacetylene 1 (128 mg, 0.5 mmol) in CH2Cl2 (100 mL), a solution of
Se2Cl2 (0.042 mL, 0.5 mmol) in CH2Cl2 (50 mL) was added dropwise at 0◦C. The reaction
mixture was allowed to warm up to room temperature and then stirred at this temperature

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L. G. SARBU ET AL.
for 8 h. The solvent was removed under vacuum, and the residue was purified by PTLC
using CH2Cl2/pentane (1:1) as eluent to give diselenide 5b (53 mg) in 22% isolated yield.
Reaction of Disulfur Dichloride with Bispropargylic Alcohols 6:
Typical Procedure
To a solution of bispropargylic alcohol (6a, 86 mg, 0.25 mmol) in diethyl ether
(30 mL), triethyl amine (0.07 mL, 0.5 mmol) was added and the reaction mixture was
cooled to –78◦C. A solution of disulfur dichloride (0.02 mL, 0.25 mmol) in diethyl ether
(15 mL) was added dropwise. After 1 h, the reaction mixture was allowed to warm
to room temperature and stirred for an additional 2 h. After the usual work-up (H2O,
NaHCO3, MgSO4), evaporation of the solvent gave the crude product as a brown viscous oil
(92 mg). NMR data of dipropargyloxy disulfide 7a were selected from the spectrum of this
oil. Purification by column chromatography on silica gel using CH2Cl2/pentane 1:1 as
eluent provided meso-ether 8a and d,l-ether 9a in a 2.5:1 ratio.
Reaction of Sulfur Dichloride with Bispropargylic Alcohols 6:
Typical Procedure
To a solution of bispropargylic alcohol (6a, 172 mg, 0.5 mmol) in CH2Cl2 (700
mL), triethyl amine (0.14 mL, 0.5 mmol) was added and the reaction mixture was cooled to
–78◦C. A solution of sulfur dichloride (0.032 mL, 0.5 mmol) in CH2Cl2 (50 mL) was added
dropwise. After 1 h, the reaction mixture was allowed to warm up to room temperature and
stirred for an additional 2 h. After the usual work-up (H2O, NaHCO3, MgSO4), evaporation
of the solvent gave the crude product that was purified by column chromatography on silica
gel using CH2Cl2/pentane 1:1 as eluent. The pinacolone 10a was obtained as white crystals
(100 mg, 61%).
REFERENCES
1. Braverman, S. In Chemistry of Sulfones and Sulfoxides; S. Patai, Z. Rappoport, C. J. M. Stirling,
Eds.; Wiley: New York, 1988; Chapters 13 and 14.
2. Braverman, S. In The Chemistry of Sulfinic Acids, Esters and Their Derivatives, S. Patai, Ed.,
Wiley: New York, 1990; Chapters 8 and 11.
3. Greiving, H.; Hopf, H.; Jones, P. G.; Bubenitschek, P.; Desvergne, J.-P.; Bouas-Laurent, H. Eur.
J. Org. Chem. 2005, 558–566.
4. Hopf, H. Angew. Chem. Int. Ed. 2003, 42, 2822–2825.
5. Hopf, H. In Modern Cyclophane Chemistry, R. Gleiter and H. Hopf, Eds., Wiley-VCH: Wein-
heim, Germany, 2004; Chapter 7.
6. Birsa, M. L.; Hopf, H. Synlett 2007, 2753–2756.
7. Braverman, S.; Cherkinsky, M.; Gottlieb, H. E.; Birsa, M. L.; Hopf, H. The 70th Annual Meeting
of the Israel Chemical Society, Bar-Ilan, Israel, February 14–16, 2005; Abstracts p. 153.
8. Maaninen, A.; Chivers, T.; Parvez, M.; Pietikaeinen, J.; Laitinen, R. S. Inorg. Chem. 1999, 38,
4093–4097.
9. Birsa, M. L.; Hopf, H. Heteroat. Chem. 2010, 21, 126–130.
10. Brauer, G. Ed. Handbook of Preparative Inorganic Chemistry, 2nd English ed.; Academic Press:
New York, 1963; Vol. 1, p. 370.

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