Exploring Green Solvents Associated to Pd/C as Heterogeneous Catalyst for Direct Arylation of Heteroaromatics with Aryl Bromides

Abstract Metal residues are certainly one of the major sources of contamination of products in metal‐catalyzed direct arylation reactions. We found that the use of only 1 mol% of the heterogeneous catalyst Pd/C promotes very efficiently the direct arylations of most heteroaromatics. In the presence of this catalyst and potassium acetate as the base, the direct arylation of thiophenes, furans, pyrroles, thiazoles, imidazoles or isoxazoles, using aryl bromides as coupling partners, proceeds highly regioselectively and in moderate to very high yields. With several heteroarenes both electron‐deficient and electron‐rich aryl bromides were tolerated; moreover, with the most reactive heteroarenes, the Pd/C catalyst tolerated green solvents such as diethyl carbonate, 3‐methylbutan‐1‐ol and pentan‐1‐ol, affording a synthetic scheme with low environmental impact. magnified image