Síntese de calcogenofenos via reações de ciclização de diinos com dicalcogenetos de diorganoíla promovida por FeCl3

Abstract

The present study reported the synthesis of a series of chalcogenophenes through the cyclization of 1,3-diynes 1 mediated by FeCl3 and dialkyldichalcogenides. First, selenophenes 2 were synthesized through the cyclization of 1,3-diynes 1 mediated by FeCl3 and dialkyldichalcogenides. A similar protocol was used to prepare thiophenes 3 using dialkyldichalcogenides, FeCl3 and iodine as additive. In order to evaluate the potential reactivity of compounds 2, the compound 2,5-diphenyl-3,4-(selenephenyl)-selenophene was submitted to a bromation reaction in the aromatic ring resulting in the formation of selenophene 4 substituted with bromine, in 65% yield, in positions 3 and 4 in the heterocyclic ring. Further, the compound 2,5 diphenyl-3,4 (methilthio)thiophene was selected as the starting material for an oxidation reaction using glacial acetic acid and hydrogen peroxide. Subsequent cyclization reaction using triflic acid led to the formation of a sulfur polycyclic 5 in 83% yield. After this, the compound 3-bromo-4-(methylthio)-2,5-diphenylthiophene 6 was selected as the starting material for the cross coupling reaction with a terminal alkyne, 1- ethynylcyclohexanol, 7 to give compound 3(cyclohexylethynyl)-4-(methylthio)-2,5- diphenylthiophene 8 in 63% yield. Moreover, compound 8 was selected as the starting material for a cyclization reaction using iodine, to give as a product 1-(3-iodo-4,6- diphenylthieno[3,4-b]thiophen-2-yl)cyclohexanol, 9 in 40% yield.