[32501-94-3]  · C8H6O2S  · Phenylsulfonylacetylene  · (MW 166.21)

(acetylene equivalent in cycloaddition reactions;2 powerful Michael acceptor;1b precursor to substituted alkynes3)

Alternate Name: ethynyl phenyl sulfone.

Physical Data: oil; bp 103-105 °C/0.01 mmHg. The 4-methyl derivative, p-TolSO2C&tbond;CH [13894-21-8], is a solid; mp 75 °C (from 95:5 hexane/ethyl acetate).

Solubility: sol common organic solvents.

Preparative Methods: a convenient preparation of the title reagent and p-TolSO2C&tbond;CH involves AlCl3-mediated substitution of one trimethylsilyl group from Bis(trimethylsilyl)acetylene by an arylsulfonyl chloride followed by hydrolysis.4 Older procedures involve oxidation of the corresponding ethynyl thioethers,5a,b diazotization of 4-arylsulfonyl-5-aminoisoxazoles,5c dehydrobromination of (Z)- and (E)-bromovinyl phenyl sulfone with fluoride ion,5d and oxidative elimination of b-(phenylseleno) vinyl sulfones.5e

Handling, Storage, and Precautions: store tightly closed and refrigerated, possibly under an inert gas. Use in a fume hood.

Cycloaddition Reactions.

Phenylsulfonylacetylene undergoes Diels-Alder addition to a number of dienes including 2,3-dimethylbutadiene, cyclopentadiene, and anthracene (eq 1).2a The resulting adducts can be reductively desulfonylated to the corresponding 1,4-dienes using Sodium Amalgam in buffered (NaH2PO4) methanol, Samarium(II) Iodide in HMPA (eq 2),2b or tin reagents.2c This reaction sequence makes arylsulfonylacetylenes equivalent to acetylene in cycloaddition reactions.6 The same sequence carried out on the adducts of tolyl trimethylsilylethynyl sulfone (TolSO2-C&tbond;C-TMS) leads to the formal adducts of trimethylsilylacetylene,7a itself a poor dienophile.7b The mildness of the reaction conditions allows the synthesis of otherwise inaccessible molecules. 7-Azanorbornadiene (eq 3)8 and [4]-peristylane (eq 4)9 are examples.

Tolylsulfonylacetylene gives ene reactions with appropriate alkenes under Ethylaluminum Dichloride catalysis (eq 5).10 In dipolar cycloadditions, arylsulfonylalkynes react with nitrile oxides and nitrile imines to give 4-arylsulfonyl-substituted isoxazoles11a and diazoalkanes (eq 6).11b They also react with sydnones11a to give 4-arylsulfonyl-substituted pyrazoles. In general, the regiochemistry of addition is opposite to that observed with Phenylsulfonylethylene. 4-Chloro-substituted pyridine N-oxides and pyridinium-N-dicyanomethylides give furopyridines11c and indolizines.11d Cycloaddition reactions have also been reported with ynamines. With these reagents the products are substituted furans (eq 7).12

Nucleophilic Additions.

Arylsulfonylalkynes display powerful Michael acceptor properties. Examples of addition include heteroatomic nucleophiles such as amines,13 hydroxylamines,14 alkoxides,15 thiols,16,17 and boranes.18 The stereochemistry of addition depends on the nucleophile and on the solvent and can be controlled to some extent to obtain the (Z) or (E) adduct. For example, 10-mercaptoisoborneol adds to phenylsulfonylacetylene in acetonitrile in a trans fashion (eq 8), affording the corresponding (Z) adduct in high yield.17 The latter was oxidized by m-Chloroperbenzoic Acid to one diastereomerically pure sulfoxide that proved to be an efficient chiral dienophile.17 Strong carbon nucleophiles such as malonate anions19 and cuprates (eq 9)20 also add to phenylsulfonylacetylene in a Michael fashion with good syn stereoselectivity depending upon the reaction conditions. Poorer nucleophiles such as organolithium and Grignard reagents can give the substitution of the phenylsulfonyl group via an electron transfer process (eq 10).3 A similar substitution occurs with the tin amide of pyrrole that permits direct stannylation of tolylsulfonylacetylene to TolSO2-C&tbond;C-SnEt3 in quantitative yield.21

Radical Additions.

The Hexabutyldistannane-promoted radical addition of alkyl iodides to phenylsulfonylacetylene (tertiary > secondary > primary) is a method to prepare (Z) adducts of a-iodo-b-alkyl-vinyl sulfones (eq 11).22a Triethylborane can replace hexabutyldistannane in such reactions.22b Functionalized vinylcyclopentenes, as mixture of stereoisomers, can be obtained from vinylcyclopropanes and the title reagent by a radical reaction initiated by phenylthio radicals (eq 12).23

1. (a) De Lucchi, O.; Pasquato, L. T 1988, 44, 6755. (b) Tanaka, K.; Kaji, A. In The Chemistry of Sulfones and Sulfoxides; Patai, S.; Rappoport, Z.; Stirling, C. J. M., Eds; Wiley; Chichester, 1988, Chapter 15, pp 791-799. (c) Simpkins, N. S. T 1990, 46, 6951. (d) Simpkins, N. S. Sulfones in Organic Synthesis; Pergamon: Oxford, 1993.
2. (a) Davis, A. P.; Whitham, G. H. CC 1980, 639. (b) Conticello, V. P.; Gin, D. L.; Grubbs, R. H. JACS 1992, 114, 9708. (c) Wnuk, S. F.; Robins, M. J. CJC 1993, 71, 192.
3. Smorada, R. L.; Truce, W. E. JOC 1979, 44, 3444.
4. (a) Bhattacharya, S. N.; Josiah, B. M.; Walton, D. R. M. Organomet. Chem. Synth. 1971, 1, 145. (b) Waykole, L.; Paquette, L. A. OS 1988, 67, 149.
5. (a) Maioli, L.; Modena, G. Ric. Sci. 1959, 29, 1931 (CA 1960, 54, 10 928g). (b) Montanari, F. G 1956, 86, 406 (CA 1958, 52, 8999h). (c) Beccalli, E. M.; Manfredi, A.; Marchesini, A. JOC 1985, 50, 2372. (d) Naso, F.; Ronzini, L. JCS(P1) 1974, 340. (e) Back, T. G.; Collins, S.; Kerr, R. G. JOC 1983, 48, 3077.
6. De Lucchi, O.; Modena, G. T 1984, 40, 2585.
7. (a) Moss, R. A.; Lukas, T. J.; Nahas, R. C. TL 1977, 3851. (b) Cunico, R. F. JOC 1971, 36, 929.
8. Altenbach, H.-J.; Blech, B.; Marco, J. A.; Vogel, E. AG(E) 1982, 21, 778.
9. Paquette, L. A.; Fischer, J. W.; Browne, A. R.; Doecke, C. W. JACS 1985, 107, 686.
10. Snider, B. B.; Kirk, T. C.; Roush, D. M.; Gonzalez, D. JOC 1980, 45, 5015.
11. (a) Dalla Croce, P.; La Rosa, C.; Zecchi, G. JCS(P1) 1985, 2621. (b) Padwa, A.; Wannamaker, M. W. T 1990, 46, 1145. (c) Abramovitch, R. A.; Deeb, A.; Kishore, D.; Mpango, G. B. W.; Shinkai, I. G 1988, 118, 167. (d) Acheson, R. M.; Ansell, P. J. JCS(P1) 1987, 1275.
12. Kosack, S.; Himbert, G. CB 1987, 120, 71.
13. Truce, W. E.; Onken, D. W. JOC 1975, 40, 3200.
14. (a) Sanders, J. A.; Hovius, K.; Engeberts, J. B. N. JOC 1974, 39, 2641. (b) Aurich, H. G.; Hahn, K. CB 1979, 112, 2769.
15. (a) Di Nunno, L.; Modena, G.; Scorrano, G. JCS(B) 1966, 1186. (b) van der Sluijs, M. J.; Stirling, C. J. M. JCS(P2) 1974, 1268.
16. (a) Montanari, F. TL 1960, 18. (b) Truce, W. E.; Tichenor, G. J. W. JOC 1972, 37, 2391.
17. (a) De Lucchi, O.; Lucchini, V.; Marchioro, C.; Valle, G.; Modena, G. JOC 1986, 51, 1457 and JOC 1989, 54, 3245. (b) De Lucchi, O.; Lucchini, V.; Marchioro, C.; Modena, G. TL 1985, 26, 4539.
18. Rasset-Deloge, C.; Martinez-Fresneda, P.; Vaultier, M. BSF 1992, 129, 285.
19. (a) Eisch, J. J.; Behrooz, M.; Dua, S. K. JOM 1985, 285, 121. (b) Ohnuma, T.; Hata, N.; Fujiwara, H.; Ban, Y. JOC 1982, 47, 4713.
20. (a) Fiandanese, V.; Marchese, G.; Naso, F. TL 1978, 5131. (b) Meijer, J.; Vermeer, P. RTC 1975, 94, 14.
21. Williamson, B. L.; Stang, P. J. SL 1992, 199.
22. (a) Curran, D. P.; Kim, D. T 1991, 47, 6171. (b) Ichinose, Y.; Matsunaga, S.; Fugami, K.; Oshima, K.; Utimoto, K. TL 1989, 30, 3155.
23. Feldman, K. S.; Ruckle Jr., R. E.; Romanelli, A. L. TL 1989, 30, 5845.

Ottorino De Lucchi

Università di Venezia, Italy

Sergio Cossu

Università di Sassari, Italy

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