Ma, X.; Xu, J.; Liu, J.; He, J.; Chang, T.; Yang, Q.; Li, N.; Qian, D.; Li, Z. Aminocyclopropenium as a New Class of Hydrogen Bonding Catalyst in Friedel–Crafts Alkylation. Catalysts2023, 13, 1370.
Ma, X.; Xu, J.; Liu, J.; He, J.; Chang, T.; Yang, Q.; Li, N.; Qian, D.; Li, Z. Aminocyclopropenium as a New Class of Hydrogen Bonding Catalyst in Friedel–Crafts Alkylation. Catalysts 2023, 13, 1370.
Ma, X.; Xu, J.; Liu, J.; He, J.; Chang, T.; Yang, Q.; Li, N.; Qian, D.; Li, Z. Aminocyclopropenium as a New Class of Hydrogen Bonding Catalyst in Friedel–Crafts Alkylation. Catalysts2023, 13, 1370.
Ma, X.; Xu, J.; Liu, J.; He, J.; Chang, T.; Yang, Q.; Li, N.; Qian, D.; Li, Z. Aminocyclopropenium as a New Class of Hydrogen Bonding Catalyst in Friedel–Crafts Alkylation. Catalysts 2023, 13, 1370.
Abstract
H-bonding, including H-bond donor (HBD) with electron-rich part of a substrate and H-bond acceptor (HBA) with electron-deficient part of a substrate, has achieved massive success. Faster transformation often correlates with more donicity of HBD. Besides the positive charge are employed to enhance the donicity of HBD, the electron withdrawing groups become a dissimilar approach for increasing the donicity of HBD. We describe newly designed H-bond donor catalysts, tris(monoalkylamino)cyclopropenium, implemented by vicinal positive charged on the cyclopropenium core. The counter anion became potential HBA to activate the electron-deficient part of a substrate. The tris(phenylamino)cyclopropenium chloride (TPAC·Cl) as a representative catalyst was applied in Friedel–Crafts alkylation of indoles with nitroalkenes. X-ray analyses of a single crystal of TPAC·Cl described the 3D architecture and the delocalized cationic charge in the solid state. Unit formal positive charge turned N–H moieties into H-bond donor (HBD) and the counter chloride anion exhibited potential H-bond acceptor (HBA). The HBD and HBA displayed cooperative organocatalysis in Friedel–Crafts alkylation of indoles with nitroalkenes. A new class of hydrogen bonding catalysis and working mechanism were proposed.
Chemistry and Materials Science, Organic Chemistry
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