The ammoximation of cyclohexanone using preformed hydrogen peroxide (H 2 O 2 ) 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, H 2 O 2 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 H 2 O 2 , 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 H 2 O 2 and TS-1, while allowing for considerable process intensification.

In this study we show that using AuPd nanoparticles supported on a commercial titanium silicate (TS-1) prepared using a wet co-impregnation method it is possible to produce hydrogen peroxide from molecular H 2 and O 2 via the direct synthesis reaction. The effect of Au: Pd ratio and calcination temperature is evaluated as well as the role of Pt addition to the AuPd supported catalysts. The effect of Pt addition to AuPt nanoparticles is observed to result in a significant improvement in catalytic activity and selectivity to hydrogen peroxide with detailed characterisation indicating this is a result of selectively tuning the ratio of Pd oxidation states.

“Silylformylation” of alkynes, which means the simultaneous introduction of a trialkylsilyl group and a formyl group into a carbon−carbon triple bond to give 3-silyl-2-alkenal, is attained selectively by the interaction of an alkyne with a monohydrosilane in the presence of Rh catalyst under CO pressure (over 10 kg/cm2). The presence of Rh catalyst is crucial for the attainment of this coupling, regardless of the types of precursors:  Rh4(CO)12, RhH(CO)(PPh3)3, [Rh(COD)Cl]2, [Rh(COD)(PPh3)2]PF6, or [Rh(COD)(DPPB)]PF6. This silylformylation is applicable to both terminal and internal alkynes. In the terminal ones, the terminal sp carbon is selectively silylated. The sp carbon bearing the bulkier substituent is formylated preferentially in internal alkynes, except for those containing a strong electron-withdrawing group. When a 1 mol excess of 1-alkynes is used under silylformylation conditions, the formation of 2-cyclopentenone derivatives is confirmed in addition to the usual silylformylation. All of these cyclopentenones are composed of two molecules of 1-alkyne and one molecule each of hydrosilane and CO. A catalyst precursor of these reactions, Rh4(CO)12, reacts almost quantitatively with hydrosilane and phenylacetylene to form Rh(CO)4SiR3 and Rh2(CO)7(phenylacetylene), respectively, under CO pressure in the stoichiometric reaction. Both of these species catalyze silylformylation with a similar efficiency to Rh4(CO)12. Furthermore, Rh(CO)4SiR3 readily reacts with phenylacetylene under a CO atmosphere to give 1,5-disilyl-2,4-diphenyl-1(Z),4(Z)-pentadien-3-one and Rh4(CO)12. On the basis of these results, a plausible pathway for silylformylation is elucidated by the sequence of the insertion of alkyne into the Rh−Si bond to form Rh−vinyl species and the subsequent insertion of CO. The insertion of another 1 mol of alkyne into Rh−vinyl species prior to CO insertion results in cyclopentenone annulations.

The ammoximation of cyclohexanone to the corresponding oxime via in-situ H2O2 formation offers an attractive alternative to the current industrial means of production, overcoming the significant economic and environmental concerns...

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The ammoximation of ketones to the corresponding oxime via the in situ production of H 2 O 2 offers a viable alternative to the current means of industrial-scale production, in particular for the synthesis of cyclohexanone oxime, a key precursor to Nylon-6. Herein, we demonstrate that using a bifunctional catalyst, consisting of Pd-based bimetallic nanoparticles immobilized onto a TS-1 carrier, it is possible to bridge the considerable condition gap that exists between the two key distinct reaction pathways that constitute an in-situ approach (i.e., the direct synthesis of H 2 O 2 and ketone ammoximation). The formation of PdAu nanoalloys is found to be crucial in achieving high reactivity and in promoting catalytic stability, with the optimal formulation significantly outperforming both alternative Pd-based materials and the monometallic Pd analogue.

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