Electrophilic cyclization of (Z)-thiobutenynes: Synthesis of 3-iodothiophenes

Organic compounds containing the thiophenic structural unit are found in various synthetic compounds useful as agrochemicals, pharmaceuticals and liquid crystals. Because of the importance of these compounds in the area of medicinal chemistry was developed an efficient methodology for preparing 3-iodotiofenos via electrophilic cyclization of (Z)-thiobutenynes. Various electrophiles and solvents were tested. For synthesis of trisubstituted 3-iodothiophenes the better electrophile and solvent for synthesis is the iodine (I2) and dichloromethane, respectively. For the synthesis of disubstituted 3-iodothiophenes 1,2-dichloroethane as solvent and iodine (I2) as eletrophile is the most suitable. Seven examples were synthesized with different substitution patterns.