An efficient protocol for synthesizing dibenzodithiapentalenes

Two new scalable methods for the synthesis of dibenzo[bc,fg]dithiapentalene (2) (DPP) are reported starting from either 1-bromo-3-fluoro-2-iodobenzene over four steps in 57% yield or from THP-protected 3-fluorothiophenol over three steps in 43% yield. Attempts to prepare dibenzodioxapentalene (15) using similar conditions were unsuccessful. Instead, we observed the formation of a macrocyclic dimeric product 16. Fluorine–hydrogen bond interactions were observed by NMR in the F/SH- and F/OH-substituted dibenzothiophene and dibenzofuran intermediates.