O-Thiobenzoquinone methides

An intramolecular hetero-Diels-Alder reaction of o-thiobenzoquinone methides, generated in situ from bis(2-formyl-phenyl)disulfide and alkenols in the presence of iodine, has been used to prepare thiochromans (Scheme 22) <2003TL6513>. 

The disulfide 32 is a stable source of o-thiobenzoquinone methides. In the presence of I2, alkenols undergo an intramolecular cycloaddition under ambient conditions to give tetrahydrofliro- and tetrahydropyrano[3,2-c]benzothiopyrans <03TL6513>. 

A series of stabilized and isolable o-thiobenzoquinone methides and related o-thioquinone methides, initially prepared by the photochemical addition of olefins to 1,2-benzodithiole-3-thione [Eq. (15)],33 34... 

The efforts on the generation and subsequent in situ Diels-Alder trap of o-thiobenzoquinone methide (16) are limited.30-32 The successful methods employed in the preparation of 16 are summarized in Scheme 8-VII, and... 

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