Ag/Se‐Catalyzed Selective Epoxidation of β‐Ionone with Molecular Oxygen

Abstract

Ag/Se could be easily fabricated by calcining selenium and silver powders. It was found to be an efficient catalyst for the selective epoxidation of the endocyclic C=C bond of β‐ionone to produce β‐ionone epoxide, an important organic intermediate in pharmaceutical industry. It is notable that the reaction can employ molecular oxygen as the cheap, clean and relatively safe oxidant, and no additives such as NHPI are required. The green process makes the method practical for large‐scale application.

Visible-light-mediated catalyst-free synthesis of trifluoromethyl(spiro)-epoxides bearing contiguous quaternary centers

“…[30][31][32][33][34][35] However, (spiro)-epoxides with continuous quaternary centers have rarely been reported via this method due to the unavailability of tetrasubstituted alkenes. 36,37 Over the last decades, visible-light-mediated organic synthesis has been recognized as a powerful and sustainable route to construct small molecules. [38][39][40][41][42][43][44][45][46][47][48][49][50][51] Indeed, the first metal-catalysed epoxide synthesis mediated by visible light (halogen lamp) was reported by Katsuki's group.…”

“…30–35 However, (spiro)-epoxides with continuous quaternary centers have rarely been reported via this method due to the unavailability of tetrasubstituted alkenes. 36,37…”

Hierarchical Titanium Silicalite-1 Zeolites Featuring an Ordered Macro–Meso–Microporosity for Efficient Epoxidations

“…Epoxides are important intermediates for fine chemicals and valuable commodities. − The catalytic epoxidation of alkenes catalyzed by titanium silicalite-1 (TS-1) zeolites using hydroperoxide as an oxidation leaves water as the only byproduct, which is a green pathway to produce epoxides. − This heterogeneous reaction follows a typical “seven-step” process, which includes (1) the diffusion of alkene molecules across the liquid–solid interface between the organic phase and TS-1 zeolites, (2) the diffusion of alkenes along the pores in TS-1 zeolites toward active Ti sites, (3–5) the adsorption, epoxidation of alkenes, and desorption of epoxides over active Ti sites, (6) the diffusion of epoxides in pores of TS-1 zeolites, and (7) the diffusion of epoxides across the solid–liquid interface into the organic phase. − The diffusion performance of the TS-1 zeolites is decisive for the whole epoxidation process. , Although TS-1 zeolites have been successfully applied as an efficient oxidation catalyst for small linear olefins, − they suffer severe intracrystalline diffusion in the epoxidation reaction with bulky substrates due to their relatively small pore size (∼0.55 nm). Consequently, bulky reactants are unable to enter into the micropores and diffuse to active sites, while large products generated on the active sites could not diffuse out of the micropores and may further convert into undesired products. − All these problems seriously restrict their applications to selective oxidation of bulky organic substrates.…”

Aerobic epoxidation of β-ionone in water under mild conditions using aldehydes as catalyst precursors

“…During the last decade, a series of methods have been developed for the selective epoxidation of β-ionone to produce 5,6-epoxy-β-ionone. 4 However, many of them employ transition metal catalysts including the expensive noble metal catalysts such as Au, 4 d Pt, 4 f and Ag, 4 b which may result in metal residues in the product, as well as the high cost of the process. 4 a – f In some cases, chemical oxidants and halogen-containing solvents were employed, which were hazardous to the environment.…”