Deprotonative metalation of five-membered aromatic heterocycles using mixed lithium-zinc species |
| |
Authors: | L'Helgoual'ch Jean-Martial Seggio Anne Chevallier Floris Yonehara Mitsuhiro Jeanneau Erwann Uchiyama Masanobu Mongin Florence |
| |
Institution: | Synthèse et ElectroSynthèse Organiques, UMR 6510 CNRS, Université de Rennes 1, Batiment 10A, Case 1003, Campus Scientifique de Beaulieu, 35042 Rennes, France. |
| |
Abstract: | Deprotonation of benzoxazole, benzothiazole, benzob]thiophene, benzob]furan, N-Boc-protected indole and pyrrole, and N-phenylpyrazole using an in situ mixture of ZnCl(2).TMEDA (0.5 equiv) and lithium 2,2,6,6-tetramethylpiperidide (1.5 equiv) in THF at room temperature is described. The reaction was evidenced by trapping with iodine, regioselectively giving the expected functionalized derivatives in 52-73% yields. A mixture of mono- and disubstituted derivatives was obtained starting from thiazole. Cross-coupling reactions of 2-metalated benzob]thiophene and benzob]furan with heteroaromatic chlorides proved possible under palladium catalysis. A reaction pathway where the lithium amide and zinc diamide present in solution behave synergically was proposed for the deprotonation reaction, taking account of NMR and DFT studies carried out on the basic mixture. |
| |
Keywords: | |
本文献已被 PubMed 等数据库收录! |
|