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Paper | Regular issue | Vol 36, No. 12, 1993, pp.2839-2850
Published online, 1st January, 1970
DOI: 10.3987/COM-93-6535
Synthesis and Reactions of N-Substituted Pyrazolo-3-sulfolenes

Ta-shue Chou* and Ruei-Chih Chang

*Institute of Chemistry, Academia Sinica, 128, Yan-Chiu-Yuan Road, Sec II, Nankang, Taipei 11529, Taiwan, R.O.C.


N-Toluenesulfonyl- and N-(anilinocarbonyl)pyrazolo-3-sulfolenes have been prepared from the protected oxotetrahydrothiophenecarbaldehyde (7) via a sequence of hydrazone formation, ketal hydrolysis, cyclization, dehydration, and oxidation reactions. These N-substituents migrate between the two nitrogen atoms of the pyrazole ring at different stages. Extrusion of SO2 from N-anilinocarbonylpyrazolo-3-sulfolenes was achieved at 180-200 °C and the transient intermediate, the pyrazolo-o-quinodimethane, could be trapped with dienophiles.