An Iodocyclization Approach to Substituted 3-Iodothiophenes
摘要:
A novel approach to 3-iodothiophenes by direct iodocyclization of alkynylthiol derivatives is presented. A variety of 1-mercapto-3-yn-2-ols 5 (readily available from alkynylation of the corresponding alpha-mercapto ketones or alpha-mercapto esters) were smoothly converted into the corresponding 3-iodothiophene derivatives 6 in good yields by reaction with molecular iodine in the presence of NaHCO3 at room temperature in MeCN as the solvent.
Synthesis of thiophenes in a deep eutectic solvent: heterocyclodehydration and iodocyclization of 1-mercapto-3-yn-2-ols in a choline chloride/glycerol medium
作者:Raffaella Mancuso、Asif Maner、Luciana Cicco、Filippo M. Perna、Vito Capriati、Bartolo Gabriele
DOI:10.1016/j.tet.2016.05.062
日期:2016.7
The heterocyclodehydration and iodocyclization of readily available 1-mercapto-3-yn-2-ols has been performed in a deep eutectic solvent (DES), that is, ChCl/Gly (1:2 molar ratio; ChCl=choline chloride, Gly=glycerol), as a non-conventional green solvent. The processes, carried out at 50 degrees C for 8 h in the presence of the PdI2/KI catalytic system or at room temperature for 5 h with 1.2 equiv of I-2, led to the formation of the corresponding thiophenes and 3-iodothiophenes in good to high yields. The DES/catalytic system could be easily recycled several times without appreciable loss of activity, after extraction of the thiophene product with hexane or Et2O. The alkynylation reaction of alpha-mercapto ketones, necessary for the preparation of the allcynylthiol substrates, was also successfully accomplished in the above protic eutectic mixture competitively with protonolysis. (C) 2016 Elsevier Ltd. All rights reserved.
Synthesis of Substituted Thiophenes by Palladium-Catalyzed Heterocyclodehydration of 1-Mercapto-3-yn-2-ols in Conventional and Nonconventional Solvents
A variety of readily available 1-mercapto-3-yn-2-ols 5 were conveniently converted into the corresponding thiophenes 6 in good to high yields in MeOH as the solvent at 50-100 degrees C in the presence of catalytic amounts (1-2%) of PdI2 in conjunction with KI (KI:PdI2 molar ratio = 10). The catalyst could be made recyclable employing an ionic liquid, such as BmimBF(4), as the solvent under suitable conditions.