Combinatorial Synthesis and Evaluation of α-Iminocarboxamide-Nickel(II) Catalysts for the Copolymerization of Ethylene and a Polar Monomer

Abstract

Late-transition metal catalysts used for olefin polymerization, the so-called postmetallocenes, which includes α-iminocarboxamide-nickel(II) catalysts have attracted a great deal of attention because of many valuable features such as the copolymerization of α-olefins with polar monomers. In this paper, the combinatorial synthesis and evaluation of α-iminocarboxamide-nickel(II) catalysts are discussed for their roles in the discovery of a highly active catalyst and elucidation of its structure-activity relationship. The combinatorial optimization of each reaction condition was performed, then a combinatorial library of α-iminocarboxamides with systematically modified substituents was constructed by amidation of α-keto acid chlorides and subsequent imination of α-keto carboxamides in parallel fashion. As a result, 87 analytically pure α-iminocarboxamide ligands were successfully synthesized. α-Iminocarboxamide-nickel(II) catalysts were prepared from the synthesized α-iminocarboxamide ligands. The catalysts' activities for polymerization of ethylene and copolymerization of ethylene and 5-norbornen-2-ol were evaluated. Results of the present study revealed 9 novel active catalysts for ethylene polymerization and 7 novel active catalysts for copolymerization of ethylene and 5-norbornen-2-ol. It should be noted that the best catalysts for ethylene polymerization and for copolymerization in the present study showed higher activities compared to the known active catalyst. Polymerization activities of the catalysts varied dramatically according to the combination of substituents on the α-iminocarboxamides.

Synthesis of the reported structure of piperazirum using a nitro-Mannich reaction as the key stereochemical determining step

“…Acid chloride 12 was prepared in situ by treatment of acid 11 with oxalyl chloride (2.00 equiv) and catalytic DMF. Subsequent reaction with diamine 21 in the presence of pyridine (1.20 equiv) and catalytic DMAP over 24 h, according to previously reported reactions for similar keto acids [49], gave only the bis-adduct 24 and none of the desired piperazinone 23 . By contrast, the reaction of carboxylic acid 11 with diamine 21 , in the presence of EDC (1.50 equiv) and 1-hydroxybenzotriazole (1.50 equiv) at rt, gave the desired product 23 in good yield (Scheme 6) [57].…”

“…Saponification of 10 with KOH provided α-keto acid 11 in excellent yield [48], and the corresponding acid chloride 12 was prepared in situ by treatment with oxalyl chloride [49]. …”

Building a Library for Catalysts Research Using High‐Throughput Approaches

“…Benefiting from the fast parallel synthesis and characterization process, HT technologies render the preparation and characterization of large variety of samples within days or even hours, greatly accelerating the efficiency of discovering and optimizing catalysts. They have proven to be powerful research strategies for the creation of libraries with vast parameter spaces such as homogeneous and heterogeneous catalysts in fuel generation, [3][4][5] organic compound synthesis, [6,7] and automobile exhaust control. [8] Generally, the requirements for HT catalyst screening are as follows: 1) manual or automated highefficiency reagents preparation; 2) a specific reaction platform to control the reaction variables, such as parallel and sequential deposition systems, solution-based reactors, and microfluidic platforms; and 3) fast parallel testing of many fabricated materials.…”

Micro-flow synthesis and structural analysis of sterically crowded diimine ligands with five aryl rings

“…Rojas and coworkers reported the synthesis of a series of bulky chelating ligands 2b–g , and detailed their use in the preparation of ethylene polymerization catalysts [18–19]. We became curious about the structure and function of 1,2,3,4,5-pentaaryl-1,3,5-triazapenta-1,4-diene ligand 3 , which is sterically more hindered, because there are as many as five aryl rings that can provide further opportunities to change and tune the steric and electrical environments of the ligands [23–24]. However, as far as we could ascertain, this has been reported only once [25].…”