1,3-DITHIOLS WITH AN ANNULATED CYCLOPENTA DIENE RING

5-Chloro-2-cyclopenten-1-ones 4 react with sodium N,N-dialkyldithiocar bamates to form the dithiocarbamic esters 5, These are cyclized by str ong acids to yield either in a Michael addition the iminium salts 6 or in a condensation reaction the iminium salts 7. Sulfhydrolysis of 7 g ives rise to the 4H-cyclopenta-1,3-dithiol-2-thione 8. By cleavage of dithiuram disulfides 10 with sodium cyclopentadienide the [(dialkylami no)thiocarbonylthio]cyclopentadienes 12 and 13 are formed. They conden se with acetone/pyrrolidine to give either the pentafulvenes 16 or the dihydropentalenes 17.