New efficient access to thieno[3,2-b]pyridine derivatives via regioselective lithiation of 3-methylthiopyridine
摘要:
The synthesis of thieno[3,2-b]pyridines was achieved using a three-step process allowing the construction of the thiophenic ring with 17-34% overall yields. The key step was the regioselective lithiation-bromination of the 3-methylthiopyridine induced by BuLi-LiDMAE superbase followed by Sonogashira coupling and halogenocyclization producing the fused heterocycles. (c) 2006 Elsevier Ltd. All rights reserved.
Cascade Radical Annulation of 2-Alkynylthio(seleno)anisoles with Acetone or Acetonitrile: Synthesis of 3-Acetomethyl- or Cyanomethyl-Substituted Benzothio(seleno)phenes
for the direct preparation of 3-aceto(cyano)methyl-substituted benzothio(seleno)phenes has been achieved throughC(sp3)–H bondactivation of easily available acetone or acetonitrile and cascade radical cyclization reaction. In this cascade radical cyclization reaction, C(sp2)–C(sp3) and C(sp2)–S bonds, as well as benzenethio(seleno)phene skeletons, can be built along with the cleavage of the C(sp3)–S
Regiocontrolled SNAr Reaction on 2,3-Dihalopyridines with NaSMe To Obtain Bromo(methylthio)pyridines as Key Precursors of 3-Halo-2-(hetero)arylthieno[2,3-b]pyridines and Thieno[3,2-b]pyridines
The synthesis of 3-halo-2-(hetero) arylthieno[2,3-b]pyridines and 3-halo-2-(hetero) arylthieno[3,2-b]pyridines has been performed through a three-step methodology from 3-bromo-2-chloropyridine or 2-bromo-3-fluoropyridine, respectively. The key step of this methodology is the formation of the required bromo(methylthio)pyridines by a regiocontrolled nucleophilic aromatic substitution (SNAr) with sodium methanethiolate (NaSMe). Then, the Sonogashira coupling with (hetero)arylalkynes followed by a halocyclization with bromine or iodine, afforded the expected 3-halo-2-(hetero)arylthienopyridines.
New efficient access to thieno[3,2-b]pyridine derivatives via regioselective lithiation of 3-methylthiopyridine
作者:Corinne Comoy、Estelle Banaszak、Yves Fort
DOI:10.1016/j.tet.2006.04.008
日期:2006.6
The synthesis of thieno[3,2-b]pyridines was achieved using a three-step process allowing the construction of the thiophenic ring with 17-34% overall yields. The key step was the regioselective lithiation-bromination of the 3-methylthiopyridine induced by BuLi-LiDMAE superbase followed by Sonogashira coupling and halogenocyclization producing the fused heterocycles. (c) 2006 Elsevier Ltd. All rights reserved.
Oxone®-mediated halocyclization/demethylation of 2-alkynylthioanisoles with sodium halides towards 3-halobenzo[b]thiophenes