The dithiole series. Part IV. Syntheses of dithiolylidene ketones and 1,6,6aS(IV)-trithiapentalenes from dithiolylium salts and of analogous compounds from pyrylium and thiopyrylium salts

Abstract

1,2- and 1,3-Dithiolylium, pyrylium, and thiopyrylium salts containing appropriately situated methylthio-groups reacted with sodium benzoylacetate to give phenacylidene-dithioles, -pyrans, and -thiopyrans. Treatment of these with phosphorus pentasulphide gave the corresponding thiophenacylidene compounds. 3-Chloro-5-phenyl-1,2-dithiolylium perchlorate reacted with 1 -pyrrolidinocycloalkenes to give pyrrolidinocycloalkenyl-1,2-dithiolylium salts which were converted into dithiolylidenecycloalkanones or trithiapentalenes, respectively, when hydrolysed or treated with potassium hydrogen sulphide. 3-Phenacylthio-1,2- and 2-phenacylthio-1,3-dithiolylium salts, with triethylamine in acetic acid, gave bis(dithiolylidenephenacyl)disulphides which were converted into phenacylidenedithioles when heated with sodium hydroxide. 3-Methyl-5-phenyl-1,2-dithiolylium perchlorate reacted with methyl dithiobenzoate to give 2,5-diphenyl-1,6,6aS(IV)-trithiapentalene and with NN-dimethylacetamide–phosphoryl chloride to give a 3-dimethylaminopropenyl-1,2-dithiolylium salt which was hydrolysed to a 3-acetonylidene-1,2-dithiole. Several trithiapentalenes were converted into 1,2-dithiolylidene ketones by hydrolysis with sulphuric acid. The electronic spectra of trithiapentalenes and of the corresponding 1,2-dithiolylidene ketones are discussed in relation to those of the corresponding 1,3-dithiolylidene, pyranylidene, and thiopyranylidene compounds.