Chroman‐4‐one‐Based Amino Bidentate Ligand: An Efficient Ligand for Suzuki‐Miyaura and Mizoroki‐Heck Coupling Reactions in Aqueous Medium

Abstract

A new family of phosphine-free Amino-chroman-4-one ((Z)-2ethoxy-3-((phenylamino)methylene)chroman-4-one) bidentate ligands ware successfully synthesised and characterised. The bidentate ligand act as efficient catalyst with combination of Pd (II) salt in the CÀ C bond formation and exhibited excellent performance in the Suzuki-Miyaura and Mizoroki-Heck coupling reaction. A broad range of substrates, including heterocyclic, flavones, Isatin and sterically hindered coupling partner, were well tolerated under the optimized reaction conditions. Metal complex and all the intermediates were formed in the catalytic cycle were characterized by mass spectrometry to support the reaction mechanism.

Design, Synthesis and Characterization of Aurone Based α,β‐unsaturated Carbonyl‐Amino Ligands and their Application in Microwave Assisted Suzuki, Heck and Buchwald Reactions

“…To confirm the metal-ligand complex, we performed a controlled experiment with the ligand A1 and PdCl 2 ratio (1 : 1) in i-PrOH at 70 °C for 5 minutes under microwave irradiation (Scheme 6). The formation of the metal-ligand complex was confirmed by 1 Based on the literature [19,33,34] and the palladium (II) complex (B) as confirmed in Scheme 6, possible catalytic cycles for Suzuki-Miyaura and Mizoriki-Heck coupling reactions are shown in Schemes 7 and 8, respectively. The complex (B) is reduced to palladium ( 0 Based on the literature, [35] intermediate (D) was formed by the oxidative addition of bromobenzene (4 b).…”

“…Several bases including Na 2 CO 3 , Cs 2 CO 3 , K 3 PO 4 , KOH, NaOAc, KOAc, KOEt, KOt-Bu, Et 3 N and piperidine (Table 3, entries 4-13) were examined and KOt-Bu was found to be the most suitable, giving product 13 a in 82% yield in isopropanol (Table 3, entry 11). A study of various solvents such as H 2 O, EtOH, t BuOH, DMF, DMSO and THF (Table 3, entry [14][15][16][17][18][19][20] showed that solvents such as t BuOH were more efficient and produced the maximum amount of product 13 a in 90% yield (Table 3, entry 17).…”

“…Based on the literature [19,33,34] and the palladium (II) complex ( B ) as confirmed in Scheme 6, possible catalytic cycles for Suzuki‐Miyaura and Mizoriki‐Heck coupling reactions are shown in Schemes 7 and 8, respectively. The complex ( B ) is reduced to palladium (0) intermediate ( C ).…”

“…explored palladium catalyzed Mizoroki‐Heck reaction using hydrazone as a ligand under phosphine free conditions [18] . Recently, Khan and co‐workers developed choman‐4‐one based N,O‐bidentate ligand and used in palladium catalyzed Suzuki‐Miyuara and Mizoroki‐Heck reaction in aqueous medium [19] …”

“…[18] Recently, Khan and co-workers developed choman-4-one based N,O-bidentate ligand and used in palladium catalyzed Suzuki-Miyuara and Mizoroki-Heck reaction in aqueous medium. [19] The palladium catalyzed, Buchwald-hartwig reaction has become the most powerful and extensively used method for the synthesis of aniline derivatives from easily available aniline and aryl halide. [20] However, the reaction conditions have suffered some limitations such as high temperature, increased catalyst loading and low to medium product yields.…”