1,4-Addition of Triazolium Thiolates to Quinones.

Article abstract of DOI:10.1021/jo00204a002

In the presence of aprotic acid, 1,2,4-triazolium-3-thiolates 1 undergo 1,4-Michael additions to quinones to fortm the corresponding thioether-substituted hydroquinones salts 2.When, however, tetrafluoroboric acid is added to a stirred aqueous suspension of triazolium thiolate 1a and p-benzoquinone, the 2,5-bis(triazolium thiolate) adduct 6, rather than the expected monoadduct 5, is isolated.Since o-quinones are extremely reactive and often difficult to isolate, they can be generated in situ by oxidation of the corresponding catechols with hydrogen peroxide in the presence of a protic acid and then trapped by a triazolium thiolate to form thioether hydroquinone salts 8.Triazolium thiolate 1a adds to a 1,4-naphtoquinone imine to give the (triazoliothio)-4-(benzenesulfonamido)-1-naphtolsalt 11.Triazoliotioquinone tetrafluoroborates 16, which can be isolated as crystalline yellow salts, are rapidly formed by oxidation of the corresponding hydroquinone salts 2 with nitrosonium tetrafluoroborate in acetonitrile.