Efficient Formation of Polycyclical Aromatic Systems Fused to a Thiadiazole Ring Using Strong Lewis or Brönsted Acids

E.L.SVARTMAN; M. F. ROZAS; OSCAR ENRIQUE PIRO; CASTELLANO, EDUARDO; MIRIFICO, MARÍA

Synthesis-Stuttgart

Georg Thieme Verlag Stuttgart

Lugar: New York; Año: 2006 p. 2313 - 2318

0039-7881

We report the efficient formation of a 9,10-dihydrophenanthrene polycyclic system fused to 1,2,5-thiadiazole 1,1-dioxide via formation of an aryl–aryl bond using strong Brønsted and Lewis acids, at different temperatures. The syntheses of the novel asymmetric 3,6-dibenzophenanthro[9,10-c]- and phenanthro[9,10-c]-1,2,5-thiadiazole 1,1-dioxides employing concentrated sulfuric or chlorosulfonic acids, or aluminum  chloride as promoters are compared. The cyclizations promoted by Brønsted acids are faster than those with aluminum chloride, but the yields are similar. On a laboratory scale the cost of reagents using Brønsted acids is one half that for the conventional procedure. The preparation and characterization of 3,4-bis (2-naphthyl)-1,2,5-thiadiazole 1,1-dioxide, the precursor of the new asymmetric 3,6-dibenzophenanthro derivative, are also described, and some aspects of its cyclization are rationalized by inspection of the results of a PM3 geometry optimization.