Cycloaddition Chemistry of Tetrafluorothiophene S,S-Dioxide.

Tetrafluorothiophene S,S-dioxide has been found to be a powerful and versatile cycloaddend that undergoes a wide range of reactions as a Diels-Alder diene, dienophile, and [2 + 2] addend. Because it dimerizes only slowly at high temperatures, a broad range of conditions are available for these transformations. Reactions with terminal alkynes yield products of both Diels-Alder and [2 + 2] cycloaddition. Remarkably, the orbital topology-forbidden [2 + 2] process sometimes dominates over the allowed Diels-Alder reaction.