Studies of heterocyclic compounds. Part X. 6a-Selenathiophthens
Abstract
4-Seleno-4H-thiopyran-4-ones are formed by treatment of 4H-thiopyran-4-ones with phosphoryl chloride in NN-dimethylformamide and subsequent addition of aqueous potassium selenosulphate. 3,5-Dimethyl-4-seleno-4H-thiopyran-4-one was isolated and characterised, but 4-seleno-4H-thiopyran-4-one and 2,6-diphenyl-4-seleno-4H-thiopyran-4-one decomposed on attempted isolation. 4-Seleno-4H-thiopyran-4-ones are ring-opened by sulphide in dimethyl sulphoxide, forming anions which undergo oxidative coupling to give 6a-selenathiophthens, a new class of heterocyclic compounds. The structure of 6a-selenathiophthens is discussed in relation to their 1H n.m.r. spectra.