1, 2‐Functionalized Imidazoles as Palladium Ligands: An Efficient and Robust Catalytic System for the Fluorine‐Free Hiyama Reaction1. Issue 4 (28th November 2013)

• Record Type: Journal Article
• Authors: Martínez, Regina; Pastor, Isidro M.; Yus, Miguel
• Is Part Of: European journal of organic chemistry. Issue 4(2014)
• Page Start: 872
• Page End: 877
• Publication Date: 2013-11-28
• Subjects: Synthetic methods -- Nitrogen heterocycles -- Palladium -- Ligand design -- Cross‐coupling; Chemistry, Organic -- Periodicals; Organic compounds -- Synthesis -- Periodicals; Bioorganic chemistry -- Periodicals; Chemistry, Physical organic -- Periodicals; 547
• DOI: 10.1002/ejoc.201301439
• Languages: English
• ISSNs: 1434-193X

Abstract

Abstract: A variety of hydroxy‐ and amino‐functionalized imidazoles were prepared from 1‐methyl‐ and 1‐(diethoxymethyl)imidazole by means of isoprene‐mediated lithiation followed by reaction with an electrophile. These compounds in combination with palladium acetate were screened as catalyst systems for the Hiyama reaction under fluorine‐free conditions using microwave irradiation. The systematic study of the catalytic system showed 1‐methyl‐2‐aminoalkylimidazole derivativeL1 to be the best ligand, which was employed under solvent‐free conditions with a 1:2 Pd/ligand ratio and TBAB (20 mol‐%) as additive. The study has revealed an interaction between the Pd/ligand ratio and the amount of TBAB. The established catalytic system presented a certain degree of robustness, and it has been successfully employed in the coupling of a range of aryl bromides and chlorides with different aryl siloxanes. Furthermore, both reagents were employed in an equimolecular amount, without an excess of organosilane. Abstract : Hydroxy‐ and amino‐functionalized imidazoles in combination with palladium acetate constitute an efficient and robust catalytic system for the fluorine‐free Hiyama reaction employing microwave irradiation. The optimal conditions were established and these were then applied to couple a range of aryl halides with aryl siloxanes.