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

ESTHER LEA SVARTMAN; MARÍA FERNANDA ROZAS; OSCAR ENRIQUE PIRO; EDUARDO CASTELLANO; MARÍA VIRGINIA MIRÍFICO*

SYNTHESIS-STUTTGART

Thieme Chemistry

Lugar: Stuttgart. Germany; Año: 2006 p. 2313 - 2318

0039-7881

Abstract: In this paper we report the efficient formation of a 9,10-dihydrophenanthrene polycyclic system fused to 1,2,5-thiadiazole 1,1-dioxide via the formation of an aryl-aryl bond using strong Brönsted 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 AlCl3 as promoters are compared. The cyclizations promoted by Brönsted acids are faster than by AlCl3, and the molar yields of the reaction product are not very different. The reagents cost, at laboratory scale, using Brönsted acids is one half that of assay performed using 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.