Sulfones pyrolysis

Dohm, J., Vdgtle, F. Synthesis of (Strained) Macrocycles by Sulfone Pyrolysis. 161,69-106 (1991). 

Benzyl salicylate, 22 16 25 184 physical properties of, 22 13t Benzyl sulfone pyrolysis, 21 141 Benzyltrimethylammonium tribromide, bromination reagent, 4 344 Bepadin, molecular formula and structure, 5 97t, 118t Bepridil, 5 104... 

With the introduction of ring contraction reactions for the preparation of [2.2] — phanes such as the sulfone pyrolysis [71] or the photoextrusion of sulfur in thiophilic solvents [72], the synthesis of thia[3 ]cyclophanes gained in significance. 

The pyrolytic elimination of sulfur dioxide from cyclic sulfones to give (strained) macrocycles (sulfone pyrolysis) counts among the most important reactions in cyclophane chemistry. There is hardly any research group dealing with cyclophanes which did not make use of the sulfone pyrolysis for the synthesis of such molecules. Since its first application in cyclophane synthesis over twenty years ago [1], the sulfone pyrolysis enabled researchers to synthesize a wealth of strained cyclophanes and developed into a reaction of general importance. 

In 1979, Rossa and Vogtle published a review on sulfone pyrolysis which did not only cover examples from cyclophane chemistry but also discussed the pyrolysis of acyclic sulfones, of small-membered cyclic sulfones as well as questions of mechanisms and practical aspects of the reaction [2]. 

Even though only httle new knowledge of theory and practice of the reactions exists, the surprising variety of successful sulfone pyrolyses described since 1979 justifies a new progress report dealing with this synthetic method as a continuation (part II) of the first review mentioned above. The following survey deals with the application of the sulfone pyrolysis on the synthesis of cyclophanes and focusses on the variety of structural types of molecules that can be synthesi d via sulfone pyrolysis. 

Oxidation of the cyclic sulfides to cyclic sulfones and subsequent thermal extrusion of sulfur dioxide in the gas phase ( sulfone pyrolysis ). 

Besides photochemical desulfurization, sulfone pyrolysis allows for the broadest range of applications. The compounds which have been synthesized belong to classes as different as heterophanes, multilayered phanes, nonbenzenoid phanes, molecules containing molecular cavities or phenylenicen . The pyrolysis of sulfones in the gas phase in comparison with other methods has many advantages ... 

It encompasses work published up to early 1990.150 different pyrolysis reactions are classified — a detailed discussion of each work is not intended. Instead — if reported in the original pubUcation — the temperature of pyrolysis, pressure, and yield of the reactions are listed in the reaction equations. For some interesting cases by-products that have been characterized are listed as well. By this treatment the scope of the sulfone pyrolysis becomes obvious. 

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