Highly efficient and organic nitrogen‐containing cation‐promoted aerobic oxidation of alkylaromatics in the presence of N‐hydroxyphthalimide

Abstract

BACKGROUD: Direct oxidation of alkylaromatics to the corresponding aromatic ketone is an important process in the manufacture of perfumes, pharmaceuticals, flavors, dyes and agrochemicals. For example, tetralin is oxidized to produce 1-tetralinone, which is a key intermediate in the commercial production of 1-naphthol, 2-hydroxy-1-tetralone, aureolic acid antibiotics and other pharmaceuticals. RESULTS: In this investigation, it was found that alkylaromatics could be efficiently and selectively oxidized to the corresponding aromatic ketones when methyl violet was employed as a promotor in the presence of N-hydroxyphthalimide (NHPI); tetralin was oxidized with 89% conversion and 76% selectivity to 1-tetralinone under 0.3 MPa of O 2 at 75• C for 2.5 h. The effects of temperature, oxygen pressure, reaction time and additive inclusion were studied in detail. A possible reaction mechanism for tetralin oxidation has been proposed. CONCLUSION: It was demonstrated that methyl violet could efficiently promote the aerobic oxidation of alkylaromatics in the presence of NHPI under mild conditions. Further investigations indicated that the nitrogen cation had a crucial promotion effect in the oxidation process.

Metal-free allylic/benzylic oxidation strategies with molecular oxygen: recent advances and future prospects

“…Cationic initiators. Based on their successfully developed biomimetic catalytic systems, Xu and his coworkers 114 continued to report the promotion effects of methyl violet, methylene blue, and methyl blue (Scheme 4) on the oxidation of tetralin [eqn (20)]. Higher selectivity of 1-tetralinone than that promoted by neutral methyl red was obtained due to their probably favorable decomposition of hydroperoxides.…”

(Z)-3-Hydroxy-4-(4-methoxyphenyl)but-3-en-2-one

“…Data collection: CrysAlis PRO (Agilent, 2012); cell refinement: CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2004); software used to prepare material for publication: publCIF (Westrip, 2010). Aromatic ketone compounds have attracted much attention due to their applications in fragrances and perfume technology (Tong et al, 2009). Studying the relationship between molecular structures and their fragrant properties remains a challenge (Griesbeck et al, 2012).…”

“…The synthesis of the compound is described by Wang & Huang (2010). For applications of aromatic ketones as fragrances, see: Tong et al (2009). For the relationship between structure and fragrance, see: Griesbeck et al (2012).…”

Efficient catalytic oxidation of methyl aromatic hydrocarbon withN-alkyl pyridinium salts

“…[30][31][32] Nitrogen-cation compounds such as methyl violet could be used as the electron-promoter to combine with NHPI in promoting the metal-free oxidation of aromatic hydrocarbon. 33,34 In nature, it was found that pyridinium cation analogues (e.g. NAD+) played an important role in the redox processes.…”