Ligand-Activated Lithium-Mediated Zincation of N-Phenylpyrrole - Université de Rennes Accéder directement au contenu
Article Dans Une Revue Chemistry - A European Journal Année : 2007

Ligand-Activated Lithium-Mediated Zincation of N-Phenylpyrrole

Résumé

Metalation of N-phenylpyrrole using an in situ mixture of ZnCl2*TMEDA (0.5 equiv) and LiTMP (1.5 equiv) was optimized. The reaction carried out at rt in THF resulted in incomplete metalation (56% conversion) and selectivity (mixture of 2-iodo and 2,2'-diiodo derivatives in a 86/14 ratio after trapping with iodine). Using DEE, toluene or hexane instead of THF, low conversions of 17, 38 or 23% were observed, respectively, but the formation of the diiodide was avoided. When hexane was used as solvent, strong lithium-complexing ligands such as 12-crown-4 and DMPU inhibited the reaction whereas more (hemi)labile ligands (TMEDA > THF ~ DME) favored it. This result shows that a temporary accessibility of lithium to interact with the rest of the base and/or the substrate is a prerequisite for an efficient metalation. A 75% yield of 2-iodo-N-phenylpyrrole was obtained after reaction with the base in the presence of 5 equiv of TMEDA for 2 h at rt, and subsequent trapping with iodine. Replacement of the spare TMP by a less expensive butyl group was attempted with success.

Domaines

Chimie organique

Dates et versions

hal-00782331 , version 1 (05-02-2013)

Identifiants

Citer

Anne Seggio, Marie-Isabelle Lannou, Floris Chevallier, Daisuke Nobuto, Masanobu Uchiyama, et al.. Ligand-Activated Lithium-Mediated Zincation of N-Phenylpyrrole. Chemistry - A European Journal, 2007, 13 (35), pp.9982-9989. ⟨10.1002/chem.200700608⟩. ⟨hal-00782331⟩
95 Consultations
3 Téléchargements

Altmetric

Partager

Gmail Facebook X LinkedIn More