Highly efficient catalytic production of oximes from ketones using in situ-generated H2O2.

The ammoximation of cyclohexanone using preformed hydrogen peroxide (H2O2) is currently applied commercially to produce cyclohexanone oxime, an important feedstock in nylon-6 production. We demonstrate that by using supported gold-palladium (AuPd) alloyed nanoparticles in conjunction with a titanium silicate-1 (TS-1) catalyst, H2O2 can be generated in situ as needed, producing cyclohexanone oxime with >95% selectivity, comparable to the current industrial route. The ammoximation of several additional simple ketones is also demonstrated. Our approach eliminates the need to transport and store highly concentrated, stabilized H2O2, potentially achieving substantial environmental and economic savings. This approach could form the basis of an alternative route to numerous chemical transformations that are currently dependent on a combination of preformed H2O2 and TS-1, while allowing for considerable process intensification.

Rhodium-catalyzed oxidative coupling of triarylmethanols with internal alkynes via successive C-H and C-C bond cleavages.

The rhodium-catalyzed oxidative coupling of triarylmethanols with internal alkynes effectively proceeds in a 1:2 manner via cleavage of C-H and C-C bonds to produce the corresponding naphthalene derivatives. Addition of tri- or tetraphenylcyclopentadiene as a ligand is crucial for the reaction to occur efficiently.

Rhodium- and iridium-catalyzed oxidative coupling of benzoic acids with alkynes via regioselective C-H bond cleavage.

The oxidative coupling of benzoic acids with internal alkynes effectively proceeds in the presence of [Cp*RhCl2]2 and Cu(OAc)2 x H2O as catalyst and oxidant, respectively, to produce the corresponding isocoumarin derivatives. The copper salt can be reduced to a catalytic quantity under air. Interestingly, by using [Cp*IrCl2]2 in place of [Cp*RhCl2]2, the substrates undergo 1:2 coupling accompanied by decarboxylation to afford naphthalene derivatives exclusively. In this case, Ag2CO3 acts as an effective oxidant.

An efficient waste-free oxidative coupling via regioselective C-H bond cleavage: Rh/Cu-catalyzed reaction of benzoic acids with alkynes and acrylates under air.

[structure: see text]. The direct oxidative coupling of benzoic acids with internal alkynes proceeds efficiently in the presence of a rhodium/copper catalyst system under air to afford the corresponding isocoumarin derivatives. The reaction forms no wastes except for water. Under similar conditions, the aerobic coupling with acrylates also takes place smoothly to produce 7-vinylphthalide derivatives via divinylation and subsequent cyclization.

Rhodium-catalyzed arylation using arylboron compounds: efficient coupling with aryl halides and unexpected multiple arylation of benzonitrile.

[reaction: see text]. The Suzuki-Miyaura-type cross-coupling of arylboron compounds with aryl halides proceeds efficiently in the presence of a rhodium-based catalyst system to produce the corresponding biaryls. Furthermore, it has unexpectedly been observed that the treatment with benzonitrile under similar conditions brings about its multiple arylation, in which nucleophilic arylation on the cyano group and subsequent ortho arylation via C-H bond cleavage are involved.