Synlett 2008(6): 911-913  
DOI: 10.1055/s-2008-1042934
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© Georg Thieme Verlag Stuttgart · New York

The Reaction of α,β-Unsaturated Sulfones with Isobenzofuran and N-Boc-isoindole Using Warrener’s Methodology

Rocío Rincón, Joaquín Plumet*
Departamento de Química Orgánica, Facultad de Química, Universidad Complutense, 28040 Madrid, Spain
e-Mail: plumety@quim.ucm.es;
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Publikationsverlauf

Received 19 December 2007
Publikationsdatum:
11. März 2008 (online)

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Abstract

The cycloaddition reaction of vinyl and acetylenic sulfones with isobenzofuran {benzo[c]furan} and N-Boc-isoindole generated in situ using Warrener’s tetrazine method is described for the first time.

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General Procedure
To equimolecular amounts of tetrazine 3, compounds 4 or 5, and sulfone 6, DMSO (10 mL/mmol) was added. The reaction mixture was stirred under Ar at r.t. for 24 h. After this time the reaction mixture was extracted with Et2O (5 mL) and washed with H2O (3 × 10 mL). The organic phase was dried over MgSO4. After removal of the solvent under reduced pressure, the crude product was purified by column chromatography (SiO2, hexane-EtOAc, 7:3).

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Compounds 7 were characterized by IR, 1H NMR, and 13C NMR spectra and mass spectral analysis. In the case of compound 7e, spectroscopic data matched with those previously reported. See ref. 10a.

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Determined by 1H NMR integration. Key signals: exo adduct: H2, δ = 3.16 ppm, dd; endo adduct: H2, δ = 3.96 ppm, dt.

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Determined by 1H NMR integration. Key signals: exo adduct: H2, δ = 3.28 ppm, dd; endo adduct: H2, δ = 4.00 ppm, dt.