Condensations of Indeno-1,2-dithioles Yielding Diindenothiopyran Derivatives

Article abstract of DOI:10.1002/ardp.19853181103

Indeno<2,1-c>-1,2-dithioles 1 "dimerize" under acid catalysis by loss of two sulfur atoms to form diindenothiopyrans 2I/II.An analogous reaction is known for 3-methyl-5-phenyl-1,2-dithiolylium perchlorate (3) which condenses in glacial acetic acid/pyridine to the isomeric thiopyrans 4I/II.Reactions of 1-acyl-2-indanones 13 in acetic anhydride/perchloric acid yield the oxygen compounds 14 and 15, which are structurally analogous to 2I/2II.