Pt-Au bimetallic nanoparticle catalysts immobilized on dimethyl polysilane (Pt-Au/(DMPSi-Al 2 O 3 )) have been developed for selective hydrogenation of quinones to hydroquinones.H igh reactivity,s electivity,a nd robustness of the catalysts were confirmed under continuous-flowc onditions. Various direct derivatizations of quinones,such as methylation, acetylation, trifluoromethanesulfonylation, methacrylation, and benzoylation were successfully performed under sequential and continuous-flowc onditions to affordt he desired products in good to excellent yields.E specially,a ir-sensitive hydroquinones,such as anthrahydroquinones and naphthohydroquinones,c ould be successfully generated and derivatized under closed sequential and continuous-flowc onditions without decomposition.
Intermolecular carbon-carbon bond-forming reaction between readily available acylsilanes and aldehydes was achieved under photoirradiation conditions with assistance of a catalytic amount of Lewis acid. Nucleophilic addition of photochemically generated siloxycarbenes to aldehydes followed by 1,4-silyl migration afforded synthetically useful α-siloxyketones. Electrophilic activation of aldehydes by Lewis acid is highly important to realize this reaction efficiently, otherwise the yield of the desired coupling products were significantly decreased. Noteworthy is that a formal cross benzoin-type reaction using acylsilanes was achieved under Lewis acidic conditions. This is the first example of Lewis acid-catalyzed reaction of photochemically generated siloxycarbenes with electrophiles.
Heterogeneous nitrogen-doped carbon-incarcerated copper nanoparticle catalysts have been developed. The catalysts showed high activity for oxidation of alcohols to the corresponding aldehydes, including aliphatic substrates, in the presence of N-oxyl...
Cooperation between light and Lewis acids gives rise to an efficient intermolecular coupling reaction between acylsilanes and aldehydes. Siloxycarbenes, generated by photoisomerization of acylsilanes, nucleophilically attack the Lewis acid‐activated aldehydes to afford synthetically useful α‐siloxyketones in good yields with wide substrate scope. More information can be found in the Communication by H. Kusama et al. on page 543 ff.
Pt–Au bimetallic nanoparticle catalysts immobilized on dimethyl polysilane (Pt–Au/(DMPSi‐Al2O3)) have been developed for selective hydrogenation of quinones to hydroquinones. High reactivity, selectivity, and robustness of the catalysts were confirmed under continuous‐flow conditions. Various direct derivatizations of quinones, such as methylation, acetylation, trifluoromethanesulfonylation, methacrylation, and benzoylation were successfully performed under sequential and continuous‐flow conditions to afford the desired products in good to excellent yields. Especially, air‐sensitive hydroquinones, such as anthrahydroquinones and naphthohydroquinones, could be successfully generated and derivatized under closed sequential and continuous‐flow conditions without decomposition.
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