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Porous Polymer for Heterogeneous Catalysis
Published in Inamuddin, Mohd Imran Ahamed, Rajender Boddula, Porous Polymer Science and Applications, 2022
Vivek Mishra, Simran Aggarwal, Shubham Pandey
N2 sorption and SEM images show that the polymer is mesoporous. Also, the CD spectra of the polymers having reverse stereochemistry showed mirror signals, proving that the polymers are chiral. After metalation with Ru species, PCP-BINAP was found to have high activity in the asymmetric hydrogenation of methyl methacrylate (Scheme 6.12). Different ketoesters with Ru/PCP-BINAP can be transformed effectively to highly enantioselective chiral alcohols. The reason for high enantioselectivity is the insertion of BINAP into the polymer, instead of grafting it on the surface of the polymer that provides uniformly distributed active sites of the catalyst and the fact that Ru species were effectively coordinated with the chiral BINAP ligand in the polymer.
Asymmetric Synthesis by Ru-BINAP
Published in Mike G. Scaros, Michael L. Prunier, Catalysis of Organic Reactions, 2017
Asymmetric Hydrogenation of Functionalized Ketones: The asymmetric hydrogenations depicted in equation 5 suggest that the key factor in enantio differentiation is the simultaneous coordination of carbonyl oxygen and hetero atom (X) to Ru(II) forming 5- or 6-membered chelate ring (Fig. 5–6). Typical examples are summarized in Table 1. It is also noteworthy that the chirality of the product is predictable by the sign of BINAP used which makes the reaction versatile.
Gelation-based visual detection of analytes
Published in Soft Materials, 2019
Wangkhem Paikhomba Singh, Rajkumar Sunil Singh
This work was closely followed by Tu and co-workers who developed a gelation-based visual sensor for chiral phosphine ligands (91). One class of small-molecule gelator is based on the aromatic-linker-steroidal (ALS) architecture. The authors reported an ALS metallogelator, 40, which formed gels in several polar aprotic solvents. π-stacking and metal–metal interactions are mainly responsible for self-assembly and subsequent gel formation. In the presence of ligands like phosphines or alkenes, the chloride ligand has a tendency to undergo ligand exchange which perturbs the self-assembled structures present in gels. The addition of one equivalent of (R)- or (S)-2,2ʹ-bis(diphenylphosphino)-1,1ʹ-binaphthyl (BINAP) to a chloroform gel of 40 resulted in its collapse. Surprisingly, when only 0.1 equivalent of phosphine ligand was used, it had a drastically different effect. The (R)-BINAP enantiomer containing gel collapsed but the (S)-BINAP did not disintegrate the gel. Further decrease in the concentration of phosphine ligand did not affect the gel’s integrity, irrespective of the enantiomer used. This enantioselective gel collapsing could be replicated with other chiral phosphine ligands.
Transition-metal-catalyzed C–N cross-coupling reactions of N-unsubstituted sulfoximines: a review
Published in Journal of Sulfur Chemistry, 2018
Akram Hosseinian, Leila Zare Fekri, Aazam Monfared, Esmail Vessally, Mohammad Nikpassand
Later, Harmata and co-workers published an efficient methodology for the synthesis of a library of N-aryl-sulfoximines 35 through cross-coupling reaction of S-methyl-S-phenyl-sulfoximine 33 with aryl chlorides 34 under microwave heating [43]. Considering the catalyst, ligand, and base, the optimized conditions of this N-arylation reaction involved using Pd(OAc)2 as a catalyst, rac-BINAP as a ligand, and Cs2CO3 as the base at 135°C under microwave irradiation for 1.5–3 h. The optimized protocol tolerated various sensitive functional groups, such as nitro, cyano, and ester functionalities and provided the expected products in moderate to excellent yields (Scheme 14(a)). The results demonstrated that under these reaction conditions the reaction of sulfoximines 33 with ortho-acyl-aryl chlorides 36 afforded corresponding benzothiazines 37 through a sequential N-arylation/condensation process (Scheme 14(b)) [43,44].