From classical to supramolecular dynamic stereochemistry: Double crystallization-induced diastereomerization of thiazine sulfonamide.

The interrelation between the configurational lability of nitrogen and sulfur atoms within the -NH-SO2 group of some thiazine sulfonamides is discussed. We have found that the compounds of the above series can crystallize as various diastereomers by the nitrogen atom, the relative configuration of the nitrogen atom determining the relative supramolecular configuration of the newly formed chiral sulfur atom. The paper presents a stereochemical transformation, which we have called "double crystallization-induced diastereomerization."

Tetramerization of 3-methyl-cyclopropene-3-carbonitrile: a novel CN-alder-ene reaction.

At elevated temperatures 3-methyl-cyclopropene-3-carbonitrile 1 was found to tetramerize giving compound 2 (3-methyl-2,3-bis(2-t-methyl-2-c-cyanocyclopropyl)-1-(2-t-methyl-2-c,3-c-dicyanocyclopropyl)-cyclopropene) in good yields. This is the first example of Alder-ene type oligomerization of a 3,3-disubstituted cyclopropene. On the basis of the product geometry and stereoselective character of the reaction, a mechanism of formation of 2 involving CN-Alder-ene reaction was proposed. DFT modeling of the mechanism has shown that the CN-Alder-ene reaction is possible as a stepwise process involving a biradical intermediate.