Vinyl sulfide Subject

There are very few examples of photolysis being used for preparation of a carbonyl ylide. The Dittami protocol follows work completed from his lab with aryl vinyl sulfides. Photolysis, followed by cycloaddition, led to the cycloadduct 305 in excellent yield and stereoselectivity. If the aryl vinyl ether 304 was subjected to irradiation in a mixed solution of toluene-methanol at 366 nm rather than a single solvent of toluene, cyclized product was obtained, but no cycloadduct was formed. If a simple phenyl aryl ether was subjected to the same tandem conditions, the cyclized product was generated, but no cycloadduct was detected. 

The need for a large excess of the vinyl ether was circumvented to some extent through the use of phenyl vinyl sulfides, as in Eq. (20) [50]. Yields of dihydrobenzofuran cycloadducts (XLVI) were generally good using only 2 equivalents of the vinyl sulfide component, although in one case (R = OMe) the cycloadduct was subject to further oxidation under constant current conditions. 

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