The reductive amination of acetophenone, (+)-camphor, and 5α-cholestan-3-one over Ru and Pd metals as well as their carbon-supported catalysts gave corresponding amines together with alcohols as ...by-products. However, we found that the corresponding amines are selectively synthesized by the addition of ammonium chloride to the reaction system with depression of the formation of alcohol, as exemplified with acetophenone. Although alcohols are usually not formed over Pd with alicyclic ketones, the alcohols formation was effectively depressed over Ru in the presence of ammonium chloride. The effects of the additive on the stereoselectivity of the formation of amines are also discussed in the cases of (+)-camphor and 5α-cholestan-3-one.
Graphical Abstract
A comparative study on the hydrogenation of norbornadiene (
I) and quadricyclane (
II) was performed over photo-assisted activated Rh
6(CO)
16 with or without UV-light irradiation. The photochemical ...and usual hydrogenations proceeded similarly as shown in reaction scheme.
The photo-assisted catalytic transfer hydrogenation and the catalytic hydrogenation of norbornadiene (
I) and quadricyclane (
II) over a photo-activated Rh cluster in 2-propanol in the presence of acetone was studied under comparative conditions. With the photo-assisted catalytic transfer hydrogenation, the hydrogen produced by dehydrogenation of 2-propanol is used very effectively for the addition to the reactants without evolving H
2. Norbornane (
IV) and nortricyclene (
V) are formed in parallel in the photo-assisted hydrogen transfer reaction of
II. In the reaction of
I, the acetone-sensitized isomerization of
I to
II occurs prior to hydrogenation in a concentration of 58
mmol/l of
I. However, at a lower concentration, we observed a stepwise hydrogenation of
I to
IV via norbornene (
III). The yield of
III formed in the catalytic hydrogenation was larger than that in the photo-assisted catalytic transfer hydrogenation. Compound
II was not observed in the catalytic hydrogenation of
I, and the yield of
V was less than 1%. Compound
II behaves in catalytic hydrogenation similar to as in photo-assisted catalytic transfer hydrogenation. The hydrogenation paths of
I and
II in both the reactions are discussed on the basis of a reaction mechanism shown in Scheme 1.
A facile and efficient synthesis of the carboxyl‐linked glucosides of bile acids is described. Direct esterification of unprotected bile acids with 2,3,4,6‐tetra‐O‐benzyl‐d‐glucopyranose in pyridine ...in the presence of 2‐chloro‐1,3,5‐trinitrobenzene as a coupling agent afforded a mixture of the α‐ and β‐anomers (ca. 1∶3) of the 1‐O‐acyl‐d‐glucoside benzyl ethers of bile acids, which was separated effectively on a C18 reversedphase chromatography column (isolated yields of α‐ and β‐anomers are 4–9% and 12–19%, respectively). Subsequent hydrogenolysis of the α‐ and β‐acyl glucoside benzyl ethers on a 10% Pd−C catalyst in acetic acid/methanol/EtOAc (1∶2∶2, by vol) at 35°C under atmospheric pressure gave the corresponding free esters in good yields (79–89%). Chemical specificities such as facile hydrolysis and transesterification of the acyl glucosides in various solvents were also discussed.
Perovskite-type LaFeO3 fine particles, prepared by a sol-gel method from an aqueous solution of nitrates, were dispersed in a dilute solution of water glass. The LaFeO3 catalyst was obtained by ...drying the suspension. The rate of LaFeO3 crystallite growth during thermal treatment was measured, and it was found that the fine particles suspended by water glass showed a highly inhabitory action against the crystallite growth of face (121).
The reductive amination of nonanal with ammonia over group 8 metals has been studied in ethanol at 50° C a nd 8 MPa-H2 to compare the selectivity of these metals for the formation of the primary ...amine (nonylamine), the secondary amine (dinonylamine) and the tertiary amine (trinonylamine). The yield of the primary amine increased in the order: Pd < Os < Pt < Rh < Ir < Raney Ni = Ru < Raney Co. High yields of the primary amine were obtained with Raney Co (94%), Raney Ni (87%) and Ru (87% ) as catalysts, while over Pd catalyst the yield was o nly 24% which was t he smallest of t he metals investigated. Over Pd and Os catalysts the secondary amine was formed in larger amounts than the primary amine (62 and 53%, respectively). The tertiary amine was formed only in small amounts over Pd an d Os catalysts (6 and 1 %, respectively). In general, the formation of t he primary amine was n ot increased by the addition of a mmonium chloride. On t he other hand, the formation of the tertiary amine was greatly increased over Pd catalyst from 6 % to 45% in the presence of ammonium chloride. The max imum amounts of the Schiff -base, N-nonylidenenonylamine, found as an intermediate during the reaction were 69% over Raney Ni, 67% over Raney Co a nd 53% over Ru which were in a ll cases much greater than the amounts of the secondary amine produced over the respective metals. These results in dicate that the reaction pathways leading to the formation of the primary amine involves t he one via th e Schiff base as the intermediate which may be decomposed into t he primary amine and 1-nonanimine, by the ad dition of ammonia. Significant amounts of N, N-dinonyl-1-nonenylamine, a tertiary amine precursor, were also formed as an intermediate during the reaction even w hen the tertiary amine was n ot formed at all. The results show that, similarly to t he Schiff base, the tertiary amine precursor may be decomposed into the secondary amine and the imine in the presence of ammonia. The different sel ectivities of catalyst metals for the formation of primary and secondary amines have been discussed on the basis of the reaction pathways which involve the isomerization of the Schiff base to the enamine.
Reductive amination of hindered alicyclic ketones has been stu died using menthone 1 and isomenthone 2 with 5% platinum metlas on carbon and Raney Ni and Co in ethanolic ammonia solution at 60°C and ...70 kg/cm2 H2 pressure. Although the reaction of 1 gave three isomeric primary amines, i. e., neomenthylamine 4, menthylamine 5 and isomenthylamine 6, no secondary amines were detected. The total yields of the primary amine isomers ranged between 24-84%, and increased in the order of Raney Ni <Raney Co<5%Pt-C<5%Rh-C≤5%Ru-C<5%Pd-C. Selectivities for the formation of the primary amine isomers also depended on catalysts used. On reaction of 1 over 5%Pd-C, 4, 5 and 6 were obtained in 45%, 16% and 23% yields, respectively. Whereas on 5%Ru-C, isomer 6 was most dominant (41%). The reaction of 2 afforded primary amine isomers in lower yields than that of 1. It is very likely that the product amines are produced via the corresponding imines as intermediates, which are in tautomeric equilibrium with the enamic forms. The observed stereochemical selectivity as well as the difference in reactivities of 1 and 2 can be accounted for by considering this tautomerism. t Reductive Alkylation. iT.
Reductive amination of 4-t-butylcyclohexanone (1) and related compounds with platinum group metals has been studied in ethanolic ammonia solution at 50°C and 80kg/cm2 H2 pressure. Selectivities for ...the formation of 4-t-butylcyclohexylamine(2) and bis(4-t-butylcyclohexyl) amine(3) depend on the platinum group metals used as the catalyst. The yields of (2) increased in the order of Pt<Os<Ir<Pd<Rh<Ru and was between 59-97%. The reaction of (1) over Pt gave (3) in as high as 34% yield, wher eas Ru did not produce (3) at all. (1) afforded cis-- (2) much more than trans- (2) over all the metals. The reaction route and the stereochemistry of the reductive amination of (1) were discussed on the basis of the formation and hydrogenation of intermediates such as 4-t-butylcyclohexaneimine(6) and Shiff's base, 4-t-butyl-N-(4-t-butylcyclohexylidene)cyclohexylamine(5). Conformation for (3) and (5) were also determined by 1H-NMR.
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