Browsing by Author "Ge, Haibo (TTU)"
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Item Ligand-promoted palladium-catalyzed β-methylene C-H arylation of primary aldehydes(2022) Yang, Ke; Li, Zhi; Liu, Chong (TTU); Li, Yunjian; Hu, Qingyue; Elsaid, Mazen (TTU); Li, Bijin (TTU); Das, Jayabrata; Dang, Yanfeng; Maiti, Debabrata; Ge, Haibo (TTU)The transient directing group (TDG) strategy allowed long awaited access to the direct β-C(sp3)-H functionalization of unmasked aliphatic aldehydes via palladium catalysis. However, the current techniques are restricted to terminal methyl functionalization, limiting their structural scopes and applicability. Herein, we report the development of a direct Pd-catalyzed methylene β-C-H arylation of linear unmasked aldehydes by using 3-amino-3-methylbutanoic acid as a TDG and 2-pyridone as an external ligand. Density functional theory calculations provided insights into the reaction mechanism and shed light on the roles of the external and transient directing ligands in the catalytic transformation.Item Palladium-Catalyzed β-C(sp3)–H Bond Arylation of Tertiary Aldehydes Facilitated by 2-Pyridone Ligands(2024) Xu, Ziting; Li, Zhi; Liu, Chong (TTU); Yang, Ke; Ge, Haibo (TTU)2-Pyridone ligand-facilitated palladium-catalyzed direct C–H bond functionalization via the transient directing group strategy has become an attractive topic. Here, we report a Pd-catalyzed direct β-C(sp3)–H arylation reaction of tertiary aliphatic aldehydes by using an α-amino acid as a transient directing group in combination with a 2-pyridone ligand.Item Photoinduced meta-Selective C-H Oxygenation of Arenes(2023) Ali, Wajid; Saha, Argha; Ge, Haibo (TTU); Maiti, DebabrataThe merger of photocatalysis and transition-metal catalysis has recently emerged as an adaptable platform for the development of innovative and environmentally benign synthetic methodologies. In contrast to classical transformation by Pd complexes, photoredox Pd catalysis operates through a radical pathway in the absence of a radical initiator. Using the synergistic merger of photoredox and Pd catalysis, we have developed a highly efficient, regioselective, and general meta-oxygenation protocol for diverse arenes under mild reaction conditions. The protocol showcases the meta-oxygenation of phenylacetic acids and biphenyl carboxylic acids/alcohols and is also amenable for a series of sulfonyls and phosphonyl-tethered arenes, irrespective of the nature and position of the substituents. Unlike thermal C-H acetoxylation which operates through the PdII/PdIV catalytic cycle, this metallaphotocatalytic C-H activation involves PdII/PdIII/PdIV intermediacy. The radical nature of the protocol is established through radical quenching experiments and EPR analysis of the reaction mixture. Furthermore, the catalytic path of this photoinduced transformation is established through control reactions, absorption spectroscopy, luminescence quenching, and kinetic studies.Item Site-Selective C−H Functionalization of Carbazoles(2023) Elsaid, Mazen (TTU); Ge, Robbie (TTU); Liu, Chong (TTU); Maiti, Debabrata; Ge, Haibo (TTU)Carbazole alkaloids hold great potential in pharmaceutical and material sciences. However, the current approaches for C1 functionalization of carbazoles rely on the use of a pre-installed directing group, severely limiting their applicability and hindering their overall efficiency. Herein, we report for the first time the development of direct Pd-catalyzed C−H alkylation and acylation of carbazoles assisted by norbornene (NBE) as a transient directing mediator. Notably, the involvement of a six-membered palladacycle intermediate was suggested in this case, representing the first example of such intermediacy within the extensively studied Pd/norbornene reactions realm.