Iron-Mediated Cyclization of 1,3-Diynyl Propargyl Aryl Ethers with Dibutyl Diselenide: Synthesis of Selenophene-Fused Chromenes

摘要

The synthesis of selenophene-fused chromene derivatives starting from 1,3-diynyl propargyl aryl ethers is reported herein. The method is based on carbon-carbon, carbon-selenium, selenium-carbon and carbon-selenium bonds formation in a one-pot protocol, using iron(III) chloride and dibutyl diselenide as promoters. The same reaction conditions were applied to propargyl anilines leading to the formation of 1-(butylselanyl)-selenophene quinolines. The results showed that the dilution and temperature of substrate addition had a crucial influence in the products obtained. When the substrates were added at room temperature, in the absence of a solvent, a mixture of products was obtained, whereas the slowly addition (15 min) of starting materials, as a dichloromethane solution, at 0 degrees C led to the product formation in good yields. The mechanistic study indicates that the cooperative action between iron(III) chloride and dibutyl diselenide was essential to promote the cyclization, whereas separately none of them was effective in promoting the cyclization. We proved the synthetic utility of heterocycles obtained in the Suzuki cross coupling reaction, giving the corresponding cross-coupled products in good yields. In addition, the organoselenium moiety was removed from the structures of products by using n-butyllithium.