Studies of heterocyclic compounds. Part XIX. Synthesis of 6,6a-dithia- and 6,6a-diselena-1,2-diazapentalenes

Abstract

1-Aryl-6,6a-dithia- and 1-aryl-6,6a-diselena-1,2-diazapentalenes, two new classes of hypervalent heterocyclic compound, have been synthesised by the reaction of 3-methyl(ene)-1,2-dithiolium and 3-methyl(ene)-1,2-diselenolium salts, respectively, with arenediazonium fluoroborates. 1-Aryl-5-t-butyl-6,6a-dithia-1,2-diazapentalenes obtained from 3-methyl-5-t-butyl-1,2-dithiolium perchlorate were accompanied by small amounts of their 3-arylazo-substitution products, which were subsequently produced in high yield by reaction of the 1-aryl-5-t-butyl-6,6a-dithia-1,2-diazapentalenes with the corresponding arenediazonium fluoroborates. The results of ¹H n.m.r. spectral studies and of X-ray crystallographic studies by other workers are discussed in relation to structure.