Supported bis(maltolato)oxovanadium complexes as catalysts for cyclopentane and cyclooctane oxidations with dioxygen

✍ Scribed by Gopal S. Mishra; João J.R. Fraústo da Silva; Armando J.L. Pombeiro

• Book ID: 103834592
• Publisher: Elsevier Science
• Year: 2007
• Tongue: English
• Weight: 926 KB
• Volume: 265
• Category: Article
• ISSN: 1381-1169
• DOI: 10.1016/j.molcata.2006.09.049

✦ Synopsis

Carbamated silica gel supported bis(maltolato)oxovanadium(IV or V) complexes, [VO(ma) 2 ] (1), [VO(py)(ma) 2 ] (2) (py = pyridine), cis-[VO(OCH 3 )(ma) 2 ] (3) and cis-[VO(OC 2 H 5 )(ma) 2 ] (4), were used as catalysts for the oxidation of cyclopentane and cyclooctane by molecular oxygen in a batch reactor, under moderate reaction conditions (typically p(O 2 ) ca. 10-14 atm, at 150-160 • C). The corresponding ketones, i.e. cyclopentanone and cyclooctanone are the main products (up to 10 and 25% yields, respectively) of the cycloalkane oxidations, but cyclopentanol and cyclooctanol are also formed in smaller amounts. The supported complex 1 shows the best activity and selectivity. The reaction is further promoted by the use of some heteroaromatic acids as co-catalysts, namely 2-pyrazine-carboxylic acid. Experiments with radical traps suggest the involvement of a free-radical mechanism.