Alkenylation of thiophenes and furans at the 2-position and a synthesis of allenes conjugated with α,β-unsaturated ester with magnesium alkylidene carbenoids
to afford thiophenes and furans bearing a fully substituted alkene at the 2-position. Treatment of the magnesium alkylidene carbenoids with 2-lithio-5-methoxyfuran afforded allenes conjugated with α,β-unsaturated methyl ester in moderate yields. These procedures offer a new and versatile one-pot synthesis of 2-alkenylthiophenes, 2-alkenylfurans, and allenes conjugated with α,β-unsaturated methyl ester
Alkenylation of thiophenes at the 2-position with magnesium alkylidene carbenoids
作者:Tsuyoshi Satoh、Natsuki Mori、Kazumi Obuchi
DOI:10.1016/j.tetlet.2007.07.074
日期:2007.9
Treatment of magnesium alkylidene carbenoids, generated from 1-chlorovinyl p-tolyl sulfoxides with isopropylmagnesiurn chloride at -78 degrees C in toluene, with 2-lithiothioplienes gave 2-alkenylated thiophenes in good to high yields. The intermediate of this reaction was found to be an alkenylmagnesium, which could be trapped with iodoalkanes and ethyl chloroformate. This procedure offers a novel and efficient one-pot synthesis of thiophenes having a disubstituted or a trisubstittited olefin at the 2-position from thiophenes in good yields. (c) 2007 Elsevier Ltd. All rights reserved.