Sterically enriched bulky 1,3-bis(N,N′-aralkyl)benzimidazolium based Pd-PEPPSI complexes for Buchwald–Hartwig amination reactions

Abstract

A simple and efficient synthesis of a series of unexisting Pd-PEPPSI complexes is summarized. These complexes are exploited for their high catalytic activity towards Buchwald–Hartwig amination.

Investigation of Pd‐PEPPSI catalysts and coupling partners towards direct C2‐arylation/heteroarylation of benzoxazole

“…Because there is a growing demand on the synthesis of new viable palladium catalysts for different organic transformations, we recently have developed an improved protocol for the preparation of a series of different symmetrical and unsymmetrical Pd‐PEPPSI complexes 1–9 [ 11 ] for C2‐arylation on N ‐substituted benzimidazolium derivatives. [ 11b ] In continuation of our efforts towards extending the scope of these catalysts for the other precursor molecules, we herein demonstrated their utility for C–H activation on benzoxazole nucleus.…”

“…Because there is a growing demand on the synthesis of new viable palladium catalysts for different organic transformations, we recently have developed an improved protocol for the preparation of a series of different symmetrical and unsymmetrical Pd‐PEPPSI complexes 1–9 [ 11 ] for C2‐arylation on N ‐substituted benzimidazolium derivatives. [ 11b ] In continuation of our efforts towards extending the scope of these catalysts for the other precursor molecules, we herein demonstrated their utility for C–H activation on benzoxazole nucleus. For optimizing the reaction condition, we have chosen benzoxazole and chlorobenzene as coupling partners and initiated an experiment in the presence of Cu(OAc) 2 and PPh 3 in toluene solvent at 110°C for 24 h in open air, but unfortunately obtained a very low product yield (Table 1, Entry 1).…”

“…This indicates that there is no significant loss of catalytic activity until three cycles after which a gradual decrease in yield can be noticed (Figure 2). The isolated catalyst after sixth cycle was characterized by scanning electron microscopy with energy‐dispersive x‐ray analysis (SEM‐EDX) and x‐ray photoelectron spectroscopy (XPS) experiments and compared with freshly prepared complex (SEM and XPS details of fresh Pd‐PEPPSI‐ 9 were discussed in detail in our previous work and recovered here for comparison [ 11b ] ). The SEM‐EDX spectroscopy experiment was performed to assess the change in palladium content in recovered Pd‐PEPPSI‐ 9 complex and observed decrease in palladium content from 9.27 (fresh complex) to 0.49 wt% (recovered complex) (Figure 3).…”

General Method of Synthesis of 5-(Het)arylamino-1,2,3-triazoles via Buchwald–Hartwig Reaction of 5-Amino- or 5-Halo-1,2,3-triazoles

“…This Buchwald–Hartwig amination is the most popular cross-coupling reaction [ 38 , 39 , 40 ] ( Figure 2 ) to access a wide range of N -mono- and N,N -disubstituted arylamines [ 41 ]. Despite impressive advances in the field, coupling of heteroaromatic amines with (het)aryl halides still remains problematic, often requiring long reaction times and time-consuming searches for optimal conditions and catalytic systems [ 3 , 42 , 43 , 44 , 45 ]. tThere are no examples of Buchwald–Hartwig cross-coupling of 5-halo- and 5-amino-1,2,3-triazoles with (het)aryl amines and halides, respectively, to afford N -aryl amino derivatives except a report on synthesis of related 4-amino-1,2,3-triazoles (with just 3 examples) [ 46 ].…”

Design, Synthesis, Characterization and Catalytic Activity in Direct Arylation Reaction of the Benzimidazole-Functionalized PEPPSI-type Pd(II)NHC Complexes bearing 4-Vynylbenzyl Group

“…(Organ, Chass, Fang, Hopkinson & Valente, 2008), bu komplekslerin farklı katalitik aktiviteleri üzerine araştırmaların artmasına neden oldu. (Boztepe, Künkül & Gürbüz, 2020;Gokanapalli, Motakatla & Peddiahgari, 2020;Jiao et al, 2020;Reddy, Anusha & Reddy, (2020) Šimůnek, Rybáčková, Svoboda & Kvíčala, 2020;Yingying et al, 2020) Son çalışmalar, Pd(II)NHC komplekslerinin Sonogashira, (Erdemir, Barut Celepci, Aktaş & Gök, 2019). Suzuki-Miyaura, (Aktaş, Barut Celepci, Gök & Aygün, 2018) Mizoroki-Heck (Borah, Saha, Sarma & Das, 2020;İmik, Yaşar & Özdemir, 2019) ve doğrudan arilasyon reaksiyonları gibi C-C birleştirme reaksiyonları için etkili katalizörler olarak çalışabileceğini göstermektedir.…”