Green Solvent Selection for Suzuki–Miyaura Coupling of Amides

Abstract

A range of environmentally friendly solvents was evaluated in the Suzuki−Miyaura coupling of amides in an attempt to provide the first solvent selection guide for the powerful C−C coupling by amide bond cleavage. Of the 14 solvents and 10 Pd−NHC catalysts (NHC = N-heterocyclic carbene) considered, i-PrOAc was identified as the recommended, environmentally friendly solvent for the coupling. The obtained data permit an overall ranking of the recommended solvents in the Suzuki−Miyaura coupling of amides, with methyl t-butyl ether (MTBE), cyclopentyl methyl ether (CPME), diethyl carbonate (DEC), p-cymene, dimethylcarbonate (DMC), and anisole as alternative recommended solvents in terms of health, safety, and environmental ranking for the coupling. The data should facilitate the replacement of hazardous solvents with green organic solvents in the biorelevant manifold of amide bond coupling for the further implementation of amide bond activation methods.

Green-Solvent Selection for Acyl Buchwald–Hartwig Cross-Coupling of Amides (Transamidation)

“…For the initial screen, we selected 14 solvents as shown in Table . The selection was based on environmental and health impact as outlined by the recent solvent selection guides − and compatibility with Pd­(II)–NHC systems. − , As a crucial selection criterion, solvents should also be readily available to the end-users in both industrial and academic settings, while their removal from the postreaction mixtures should be facile. Neolyst CX31, [Pd­(IPr)­(cin)­Cl], IPr = 1,3-bis­(2,6-diisopropylphenyl)­imidazol-2-ylidene, was selected as the Pd­(II)–NHC catalyst for the initial screen because of its robustness, commercial availability, and the high activity in the amide cross-coupling. , DME has been included for comparison as a benchmark.…”

Mechanistic Aspects of the Palladium‐Catalyzed Suzuki‐Miyaura Cross‐Coupling Reaction

“…Indeed, the inorganic boron‐based by‐product can be easily removed after the reaction. In addition, they can react under mild conditions as well as under aqueous solvent and heterogeneous conditions [34] . The reaction is only slightly affected by steric hindrance and has a wide tolerance for a broad range of functional groups [35] .…”

“…In addition, they can react under mild conditions as well as under aqueous solvent and heterogeneous conditions. [34] The reaction is only slightly affected by steric hindrance and has a wide tolerance for a broad range of functional groups. [35] More importantly, the coupling proceeds with high regio‐ and stereoselectivity.…”

An efficient and straightforward approach for accessing thionoesters via palladium-catalyzed C–N cleavage of thioamides

“…Since the first report in 2015, 39 rapid and profound progress has been made on the selective C–N bond cleavage of activated amides via a transition-metal-catalyzed system. Szostak, 40–57 Garg, 58–68 Zou, 69–71 Yamaguchi, 72–76 Huang, 77–83 Shi, 84–86 and Rueping 87–89 have made great contributions to the study of amide transformation. Our group 90–105 has also conducted excellent research in this field.…”