Sulfur heterocycles, photochemistry

The photoelimination of nitrogen from azo compounds, diazo compounds, and azides is a topic that has been thoroughly reviewed elsewhere. These transformations are found in oxygen and sulfur heterocycles, but as they are not unique to these systems, they will not be discussed in this article. Examples can be found in a review on the photochemistry of nitrogen-containing heterocycles.1... 

Professor Yates made important contributions to organic photochemistry, mechanistic organic chemistry, synthetic methods, and spectroscopy of organic compounds. His most important work in photochemistry was discovery of the photorearrangement of cyclic ketones to oxacarbenes. His studies of alpha-diazoketones led to syntheses of novel nitrogen and sulfur heterocycles. Among his many contributions to synthetic methodology was his discovery that some Oiels-Ajper reactions can be accelerated by Lewis acids. 

Saturated three- and four-membered heterocyclics absorb little in the readily accessible regions of the UV spectrum. Sulfur-containing rings are an exception, as can be seen in Table 9, Despite the lack of absorption of most parent compounds, there is a wealth of photochemistry of small heterocyclics. Light absorption by substituents, and energy transfer from photoexcited molecules present in the photoreactive system make photoconversion of the heterocycles practical. On the other hand, the lack of substantial absorption of their own can be exploited in the preparation of small heterocycles, by designing the system to be unsuitable for destructive energy transfer. 

Heterocycles, 11, 1 The Photochemistry of Oxygen- and Sulfur-Containing Heterocycles, 33, 1 Photochemistry of Nitrogen-Containing Heterocycles,... 

Rees, C. W., Smithen, C. E., The Reactions of Heterocyclic Compounds with Carbenes, 3,57. Reid, S. T., The Photochemistry of Heterocycles, 11,1 The Photochemistry of Oxygen- and Sulfur-Containing Heterocycles, 33, 1 Photochemistry of Nitrogert-Containing Heterocycles, 30, 239. 

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