Newman–Kwart rearrangement

The Newman - Kwart rearrangement ( also thiono thiolo rearrangement) is a chemical reaction that can migrate through which the oxygen aryl Thionourethane at higher temperatures in the isomeric Thiolourethane. For Thionkohlensäureester the thiono thiolo rearrangement was discovered in 1930 by the German chemist Alexander Schönberg ( 1892-1985 ) first described. Newman and Kwart being transferred to thiocarbamates. Since then, the broader designation Newman Kwart rearrangement is used for rearrangements of this kind.

Within a multistep reaction sequence can be personalized with the Newman - Kwart rearrangement phenols converted into Thiophenols. This, first, the phenol is converted to the Thionourethan then rearranged to Thiolourethan and then digested with caustic soda to thiophenol.

The first examined in the gas phase rearrangement can be carried out under microwave irradiation in solution. Electron-withdrawing groups in the para position of the aryl group accelerate the rearrangement. Mechanistically, the rearrangement proceeds apparently via an ipso- substitution with a four -membered transition state, but higher substrate concentrations in solution and a bimolecular transition state is discussed with achtgliedrigem ring.