SYNTHESIS AND RELATIVE DIATROPICITY OF A REMARKABLY AROMATIC THIA[13]ANNULENE

2,4-Bis(bromomethyl)-3-methylthiophene was synthesised as an intermedi ate to prepare the strained thiophenobenzophanediene 11, which readily thermally valence isomerizes to the novel thia[13]annulene 10. This t hia-annulene is notably diatropic and shows about 40% of the ring curr ent of the parent bridged [14]annulene 9, which is substantially more than an analogous oxaannulene, 18, and substantially less than the aza annulene 19.