For the reaction of α,β-unsaturated ketones with electron-rich arenes catalyzed by gold(III) chloride both, a Friedel–Crafts-type mechanism and an initial metallation, are evaluated. Gold(III) chloride has proven to be an efficient catalyst under very moderate reaction conditions, however, in the case of sterically demanding products HBF4 turned out to be the superior catalyst.

Gold(III) Chloride-Catalyzed Addition Reactions of Electron-Rich Arenes to Methyl Vinyl Ketone

Microwave radiation has recently become an active source of thermal energy in numerous chemical reactions As such, the microwave energy is not ordinarily and is not likely to be used to drive photochemical reactions Accordingly, is the role of microwaves then relegated solely to be a source of heat? They do not have to be since photochemical reactions can be activated indirectly by microwaves using the UV light emitted from certain gas-fills excited by microwave radiation This article examines the microwave radiation not only as a dielectric heat source but also a source of vacuum-UV radiation and UV light through microwave discharge electrodeless lamp devices, which in some cases (depending on design) can also serve as photoreactors

Photochemistry with microwaves: Catalysts and environmental applications

Ultrasonically improved reductive properties of an aqueous ZnNiCl2 system-1 selective reduction of α,β-unsaturated carbonyl compounds

We report a Rh-catalyst for accessing olefins from primary alcohols by a C–C bond cleavage that results in dehomologation. This functional group interconversion proceeds by an oxidation-dehydroformylation enabled by N,N-dimethylacrylamide as a sacrificial acceptor of hydrogen gas. Alcohols with diverse functionality and structure undergo oxidative dehydroxymethylation to access the corresponding olefins. Our catalyst protocol enables a two-step semisynthesis of (+)-yohimbenone and dehomologation of feedstock olefins.

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Tandem Catalysis: Transforming Alcohols to Alkenes by Oxidative Dehydroxymethylation

The first general route for nickel-catalyzed transfer hydrogenation reaction of alkenes and alkynes using water as the hydrogen source has been developed. The method features the use of inexpensive and air-stable nickel(II) salt as the pre-catalyst and zinc powder as a reducing agent, allowing the TH reaction to occur under mild reaction conditions with a wide substrate scope and functional group tolerance. No ligand was required for this reaction. The reaction has also been applied successfully to the reduction of nitrogen-containing heterocycles.

https://pubs.rsc.org/en/content/articlepdf/2019/qo/c9qo00616h

Ligandless nickel-catalyzed transfer hydrogenation of alkenes and alkynes using water as the hydrogen donor

It was found that various organic compounds were reduced in good yields by refluxing them with precipitated metals in water. Water was proved to be indispensable as a hydrogen donor. The reduction of compounds which are insoluble in water was facilitated by using a mixture of dioxane and water. It is of interest that the reduction of nitriles with this catalyst afforded the hydrochlorides of the corresponding primary amines. The results imply the participation of the chloride ion on the ppt-metal catalyst. A selective reduction of C=C was observed in some α,β-unsaturated ketones, such as mesityl oxide and 1,3-diferrocenyl-2-buten-1-one. The relative activity of the various precipitated metals depends not only upon the kinds of the metals but also upon their combination. It is assumed that the surface of the ppt-Ni is acidic as a result of the coexisting chloride ion, which might participate in the catalytic reaction.

Novel Reduction of Various Organic Compounds with Water in the Presence of Precipitated Metals

Benzyl alcohol was dehydrogenated to benzaldehyde when it was heated in the presence of various metal catalysts. It was found that the dehydrogenation was accompanied by a reductive dehydroxylation and dehydroxymethylation which led to the production of toluene and benzene respectively. The compositions of the products, which mainly consisted of benzaldehyde, toluene, and benzene, were greatly affected by the chemical nature of the catalysts used. The results of the reactions in a sealed tube or in an authoclave suggested that a pseudo-equilibrium between benzyl alcohol and benzaldehyde was attained during the reaction in a closed system. The formation of CO2, CH4, and other hydrocarbons as gaseous products was also observed. From these results, the catalytic dehydrogenation, dehydroxylation, and dehydroxymethylation were assumed to proceed competitively via a certain metal benzyl complex which is formed as an adsorbed transition complex upon the catalyst metal.

The Catalytic Dehydrogenation, Dehydroxylation and Dehydroxymethylation of Benzyl Alcohol. I. The Scope and the Kinetic Study

This paper will describe the reaction of benzyl alcohol in the presence of various kinds of modified stabilized nickel catalysts, which had been prepared from the mother catalyst by treating it with solutions of appropriate metal chlorides. The catalytic activities of each modified catalyst for the formation of benzene, toluene, and benzaldehyde were compared in terms of the fH,fCH3, and fCHO values; the selectivities for the formation of benzene and toluene against that of benzaldehyde, SH and SCH3, were also evaluated. In general, the formation of toluene and benzene was greatly affected both by the kind and by the amount of metal chlorides used as additives. The reaction was promoted by the addition of a proper quantity of alkali metal chloride. In the cases of the reactions by lowlymodified catalysts, the decreasing order of the fH and fCH3 values according to the kind of metal ion adsorbed on the catalyst was as follows: Na+≥K+>Co2+>Ca2+>Cd2+>Ba2+>Hg2+>Cu2+. On the other hand, in the higher degrees o...

The Catalytic Dehydrogenation, Dehydroxylation, and Dehydroxymethylation of Benzyl Alcohol. III. The Effect of Metal Chlorides as Additives

The reaction of benzyl alcohol has been examined over stabilized nickel (S-Ni) catalysts which have been modified by treating the catalyst surface with solutions of sodium compounds; this has been done in order to obtain some information about the relation between the behavior of the molecule adsorbed on the metal catalyst and the chemical nature of the catalyst surface. On the basis of the fH, fCH3, and fCHO values, which were defined as representing the catalytic activity for the formation of benzene, toluene, and benzaldehyde respectively, the variation in the activity for each modified S-Ni was evaluated. The general aspects may be summarized as follows: (1) The reaction is generally retarded with an increase in the amount of a sodium compound which is adsorbed on the catalyst during the modification process. (2) When the modification is of a lower grade, the effect of additives on the catalytic activity represented by f values is in the following order: NaNO3<NaOH<Na2S2O3<NaI<NaBr<NaCl. (3) A proper ...

The Catalytic Dehydrogenation, Dehydroxylation, and Dehydroxymethylation of Benzyl Alcohol. II. The Effects of Sodium Compounds as Additives

The ppt-metal-catalyzed reduction, which is performed by refluxing the substrates with water in the presence of ppt-metals, was investigated in detail. The participation of water as a hydrogen donor was demonstrated by the fact that benzaldehyde was reduced to the corresponding deuterated alcohols when heated with D2O in the presence of ppt-Ni. The scope of the reduction was established by the reaction of cyclohexanone with ppt-metals and water. The most preferable H2O/cyclohexanone molar ratio was found to be about 15 : 1. The reaction was accelerated when a 0.25N aqueous solution of sodium chloride was used instead of water. It was found that the order of the abilities of various ppt-metals to decompose water is different from that of the abilities to catalyze the reduction of cyclohexanone. The values of the activation energies for the reduction catalyzed by ppt-Ni and ppt-Ni,Co were found to be 4.0 kcal/mol and 7.5 kcal/mol respectively. From these facts, it was concluded that the ppt-metal-catalyzed ...

Masayoshi Ishige

Papers

Novel Reduction of Various Organic Compounds with Water in the Presence of Precipitated Metals

The Catalytic Dehydrogenation, Dehydroxylation and Dehydroxymethylation of Benzyl Alcohol. I. The Scope and the Kinetic Study

The Catalytic Dehydrogenation, Dehydroxylation, and Dehydroxymethylation of Benzyl Alcohol. III. The Effect of Metal Chlorides as Additives

The Catalytic Dehydrogenation, Dehydroxylation, and Dehydroxymethylation of Benzyl Alcohol. II. The Effects of Sodium Compounds as Additives

A Novel Reduction in the Presence of Precipitated Metals. II. The Behavior of Precipitated Metals and Water in Catalytic Reduction