A cyclic thioketone as biradical heterocyclopentane-1,3-diyl: synthesis, structure and activation chemistry

The reaction of the biradical [(mu-NTer)P](2) with thiophosgene, SCCl2, leads to a cyclic phospha-aza thiourea derivative in very good yields. This synthetic approach represents a new possibility to prepare cyclic thioketones starting from four-membered cyclo-diphosphadiazanediyls by formal CS insertion with simultaneous oxidation of the two phosphorus atoms by the two chlorine atoms. When the phospha-aza thiourea derivative is reduced with magnesium chips, a deep blue, highly labile cyclic thioketone is formed, which can be regarded as a biradical heterocyclopentane-1,3-diyl. This new biradical can be converted to a housane species by light, which triggers transannular P-P bond formation. A thermal back-reaction was not observed, but scavenging reactions with CS2 or PhCHO clearly indicate the intermediate formation of the labile, biradical cyclic thioketone. Various intercepted products, such as [2.2.1]bicyclic cage compounds could be isolated and structurally characterized. Freshly in situ generated biradical thioketone can be utilized to activate small molecules.

Automated summary

This study describes the synthesis of a cyclic phospha-aza thiourea derivative through the reaction of a biradical with thiophosgene. The resulting cyclic thioketone, formed by reducing the phospha-aza thiourea derivative, exhibits unique properties as a biradical heterocyclopentane-1,3-diyl. Furthermore, this biradical can be converted to a housane species by light, triggering the formation of transannular P-P bonds.