New highly brominated Mn-porphyrin: a good catalyst for activation of inert C–H bonds

• Published in: RSC advances 2015-01, Vol.5 (129), p.106589-106598
• Main Authors: Santos da Silva, Vinicius, Nakagaki, Shirley, Ucoski, Geani Maria, Idemori, Ynara Marina, DeFreitas-Silva, Gilson
• Format: Article
• Language: English
• Subjects: Activation; Catalysts; Catalytic activity; Chlorides; Cyclohexane; Imidazole; Inert; Oxidation
• ISSN: 2046-2069; 2046-2069
• DOI: 10.1039/C5RA20690A

This work describes the synthesis and characterization of a novel third-generation catalyst 5,10,15,20-tetrakis-(4′-bromine-3′,5′-dimethoxyphenyl)-2,3,7,8,12,13,17,18-octabromoporphyrinatomanganese chloride [Mn III Br 12 T3,5DMPP]Cl (Cat.2). The catalytic activity of Cat.2 in cyclohexane, adamantane, and n -hexane oxidation by iodosylbenzene (PhIO) or iodobenzene diacetate (PhI(OAc) 2 ) was compared with the catalytic activity of [Mn III T3,5DMPP]Cl (Cat.1), a second generation catalyst. The Cat.2/PhI(OAc) 2 system led to higher yields of cyclohexane oxidation products (65%) with high selectivity for cyclohexanol (86%) as compared with Cat.1 (19% and 74%, respectively) and addition of water essentially did not alter total product yield. Addition of a small amount of imidazole to the Cat.1/PhIO system gave superior yields of cyclohexane oxidation products (64%) as compared with Cat.2 (52%). In all systems Cat.2 afforded significantly higher yields of 2-adamantanol, a product with great commercial value compared with 1-adamantanol. n -Hexane oxidation gave low total product yield; Cat.2 was more selective for alcohol products (2-hexanol and 3-hexanol).