Copper-catalyzed double C–S bond formation for the synthesis of 2-acyldihydrobenzo[b]thiophenes and 2-acylbenzo[b]thiophenes†
An efficient domino process is developed for the synthesis of diversely substituted 2,3-dihydrobenzo[b]thiophenes from 2-iodoketones using a Cu-catalyst and easily available xanthate as a sulfur surrogate in good yields. This domino method has been expanded for the synthesis of 2-acylbenzo[b]thiophenes using in situ generated iodine (I2) from by-product KI in high yields. Treatment of xanthate with the copper(II)-catalyst reduced it to a Cu(I)-catalyst, which initiates the catalytic cycle. A possible mechanism has been proposed based on the results from XPS-analysis, an iodine color test and several other control experiments.