Cer(IV)oxidationen von β‐Aminoketonen, 8. Mitt.: Synthese von im Piperidinteil verschieden substituierten 1,2,3,4‐Tetrahydroisochinolinen

Holzgrabe, Ulrike; Inkmann, E.

doi:10.1002/ardp.19933260406

Cited by 6 publications

(1 citation statement)

References 17 publications

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“…In particular, ketonic tert-Mannich bases and their quaternary salts have been employed frequently as potential intermediates in the synthesis of a multitude of heterocycles of pharmaceutical interest, such as pyrazolines [9 -11], pyridines [3], piperidines [14 -16], 1,5-benzo-or 1,5-hetero-diazepines [16 -19], and quinolines [20]. The use of secMannich bases as synthetic intermediates has been reported in a limited number of cases for the synthesis of pyrimidines [21], quinolines [22,23] and isoquinolines [24,25], and recently we reported [16] the synthesis of the 2H-1,2,4-triazepine ring system starting with ketonic sec-amine bases.…”

Section: Introductionmentioning

confidence: 99%

Mannich Bases as Synthetic Intermediates: Convenient Synthesis of Functionalized 1,2,4-Triazepines, 1,4-Diazepines and 1,5-Diazocines

Afsah

Keshk

Abdel-Rahman

et al. 2011

Zeitschrift Für Naturforschung B

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Transamination between the ketonic Mannich bases 1a, b and primary arylamines gave a series of ketonic sec-Mannich bases 2a -h. A variety of tetrahydro-1,2,4-triazepines 3a -f have been synthesized by treating the arylhydrazones of 2 with formaldehyde. A similar reaction with the benzenesulfonylhydrazone of 2b afforded 4. The 3-styryl-2H-1,2,4-triazepine 5 was obtained from the phenylhydrazone of 2a and cinnamaldehyde. Treatment of arylhydrazones of the 4-methoxystyryl keto base 7 with formaldehyde and cinnamaldehyde afforded the 3,4,5,6-tetrahydro-2H-1,2,4-triazepines 8a, b. Mannich reaction with 4-(p-hydroxyphenyl)-tetrahydro-1,2,4-triazepine 3d afforded the Mannich bases 9, 10 and 11.The reaction of 1b with o-phenylenediamine leads to the 1,5-benzodiazepine 13. The new tetrahydro-1,4-diazepine and tetrahydro-1,5-diazocine Mannich bases 15 and 17 were obtained from 1b and ethylenediamine or 1,3-diaminopropane, respectively. The bi(piperidine) derivative 19 was obtained from 1a and 1,3-diaminopropane.

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Section: Introductionmentioning

confidence: 99%

Mannich Bases as Synthetic Intermediates: Convenient Synthesis of Functionalized 1,2,4-Triazepines, 1,4-Diazepines and 1,5-Diazocines

Afsah

Keshk

Abdel-Rahman

et al. 2011

Zeitschrift Für Naturforschung B

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Reductive Aminations of Carbonyl Compounds with Borohydride and Borane Reducing Agents

2002

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Reductive amination is an important tool for synthetic organic chemists in the construction of carbon‐nitrogen bonds. This reaction, also termed reductive alkylation, involves condensation of an aldehyde or ketone with an amine in the presence of a reducing agent. A wide variety of substrates can be used including aliphatic and aromatic aldehydes and ketones, and even benzophenones. A range of amines from ammonia to aromatic amines, including those with electron‐withdrawing substituents, can be employed. For particularly sluggish reactions, such as those involving weakly electrophilic carbonyl groups, poorly nucleophilic amines, or sterically congested reactive centers, additives such as molecular sieves or Lewis acids are often useful. This chapter focuses on those conditions in which the carbonyl component, amine, and reducing reagent react in the same vessel. This review is restricted to reductive aminations using borohydride and borane reducing agents. This chapter concentrates on reductive amination chemistry mediated by borohydride and other boron‐containing reducing agents from 1971, the year when sodium cyanoborohydride was introduced, through the middle of 1999. In addition to reductive aminations of aldehyde and ketone substrates, reactions of related structures including acetals, aminals, ketals, carboxylic acids, nitriles, and dicarbonyls that form a nitrogen‐containing ring are reviewed. Intramolecular processes in which the substrate contains both the carbonyl and amine moieties are described. The intramolecular variant is a useful method for preparing cyclic amines. All of the various boron‐containing hydride sources in reductive aminations, including labeled metal hydrides, are reviewed. Instances of reductive aminations that failed are described. Applications of this method to a solid support in parallel synthesis in combinatorial chemistry as well as reductive aminations that proceed in tandem with a second reaction such as reductive lactamizations are discussed.

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Cerium(IV)oxidations, Part IX: Cyclization of Diethyl 4‐Phenylbutane‐1, 1‐dicarboxylate

Holzgrabe

Reinhardt

Stoll

1993

Archiv der Pharmazie

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The oxidative cyclization of N-benzyl-P-aminoketones using cerium(1V)sulphate is a valuable method for the synthesis of various substituted 1,2,3,4-tetrahydroiso-q~inolines*-~). Investigations of the reaction mechanism showed the formation of an oxoalkyl radical in the first step followed by a radical aromatic substitution. In order to gain more insight into the mechanism of the oxidative cyclization we extended our investigations to nitrogen-free systems such as diethyl 4-phenylbutane-1,1 -dicarboxylate (1).Methyl acetoacetate and acetylacetone6) give ESR signals charaFteristic of the corresponding oxoalkyl radicals R-C(CS=O)~ (measured in a flow cell in sulfuric acid in the presence of cerium(IV)sulphate, go = 2.01 56 and 2.0052, respectively). Therefore, it is probable that the phenylbutane dicarboxylate 1 will also form an oxoalkyl radical which is able to attack the phenyl ring forming a tetrahydronaphthalene derivative. Due to the poor solubility of 1 in sulfuric acid the reaction was performed in glacial acetic acid using cerium ammonium nitrate (CAN).First oxidations of diethyl 4-phenylbutane-l , 1 -dicarboxylate (1) were carried out in glacial acetic acid containing 0.3% water at 80°C and a molar ratio of substrate/CAN = 1:2. The reaction was terminated after 3 h by addition of water. Four derivatives could be isolated from the reaction by means of column chromatography, and the structures were elucidated by 'H-NMR, I3C-NMR and mass spectroscopic data: The expected cyclization product 2, a nitro derivative 4, and an alcohol 3 as well as the corresponding acetate 5 (Scheme 1). In contrast to other CAN-oxidations of comparable compounds, e.g. esters of 5-aryl-3-oxopentanoic acids'), no n i t r e derivative was obtained.The structure of the nitro product 4 has been assigned by means of EI-MS and IR-spectra: The loss of 46 mu observed in El-MS results from a loss of NO2 proved by high resolution measurement of this peak. No loss of NO was observed. These data exclude a R-0-N=O structure whose formation is also likely during the reaction. A further hint for the R-N02 structural element is the IR-absorption at 1570 cm-'. 985 Scheme 1: Oxidation of diethyl4-phenylbutane-1, I -dicarboxylate (1)To find out the reason for the formation of the different products, the reaction was carried out in presence of various amounts of water and at different temp.. The distribution of products was analysed by the means of gas chromatography. In almost non-aqueous systems (less than 0.015% water, determined by Karl-Fischer titrations) the formation of mainly the nitro-and alcohol-derivatives was observed, only a small amount of the cyclic product 2 could be detected. The yield of 2 increased significantly upon increasing the water content. It should be stressed that even in the presence of 0.05% water, the amount of cyclization product surpassed the others. Beyond 3% water the relative amounts of the products remained constant (Fig. 1). Increasing temp. (between 20°C and 80"C, 0.3% of water) also influenced the distribution of...

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Cer(IV)oxidationen von β‐Aminoketonen, 8. Mitt.: Synthese von im Piperidinteil verschieden substituierten 1,2,3,4‐Tetrahydroisochinolinen

Cited by 6 publications

References 17 publications

Mannich Bases as Synthetic Intermediates: Convenient Synthesis of Functionalized 1,2,4-Triazepines, 1,4-Diazepines and 1,5-Diazocines

Mannich Bases as Synthetic Intermediates: Convenient Synthesis of Functionalized 1,2,4-Triazepines, 1,4-Diazepines and 1,5-Diazocines

Reductive Aminations of Carbonyl Compounds with Borohydride and Borane Reducing Agents

Cerium(IV)oxidations, Part IX: Cyclization of Diethyl 4‐Phenylbutane‐1, 1‐dicarboxylate

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