Emde reduction

Both Swinkels et al. [7] and Chabre and Pannetier [9] described the process of EMD reduction as three overlapping processes. Recently Donne et al. reported [9] that the presence of Bi (OH)3 on the EMD surface modified the discharge curve considerably and the rechargeability was increased. Formation of the bimessite structure from EMD and Bi (OH), or Bi203 (mechanically mixed with EMD) [11] is the cause of the increase in rechargeability. 

The lithium aluminum hydride reduction of225 afforded two products, namely 227 and 228. Emde reduction, however, gave only 227. By contrast, lithium aluminum hydride gave a single product from 224, but lithium in liquid ammonia produced multiple products. Thus either method may be selective, depending on the nature of X. The Emde method has also been applied to 9-cyanoindolizidines with the formation of medium-ring amides.267... 

Much attention has been directed to the possibility that gelsemine is an allylamine. The Emde reduction normally proceeds readily with allylammonium salts, but gelsemine methiodide, with sodium in liquid... 

The sodium amalgam (Emde) reduction of vomicine metho salts (CCLIV) in dilute acetic acid gives two products (195, 203) base I, which has structure CCLVII (R = CH3) (202), and base II, the structure of which is not proved (202, 203). Why allylic hydrogenolysis does not occur is not known. Base I is demethylated to a secondary alcohol CCLVII (R = H) (203), which could not be oxidized by the Oppenauer method back to vomicine (202), nor could vomicine be reduced to it. 

Yellow deoxyvomicine reacts with dimethyl sulfate in boiling benzene to give a pale yellow quaternary methosulfate. Although the direct isomerization of this to the colorless quaternary salt derived from colorless deoxyvomicine and methylsulfate is not reported, it probably occurs under the alkaline conditions of the Emde reduction with Na/Hg, for the main product there is identical with base CCLXII, obtained from the quaternary methochloride of colorless deoxyvomicine (CCLXI) (202). 

Nicotinamide is the reactive moiety of the nicotinamide nucleotide coenzymes NAD (nicotinamide adenine dinucleotide) and NADP (nicotinamide adenine dinucleotide phosphate), which are coenzymes (or more correctly cosubstrates) in a wide variety of oxidation emd reduction reactions (Section... 

The nicotincunide coenzymes cire involved as proton and electron carriers in a wide vcuiety of oxidation emd reduction reactions. Before their chemical structures were known, NAD emd NADP were known as coenzymes I and n. Later, when the chemiccd nature of the pyridine ring of nicotinamide was discovered, they were Ccdled diphosphopyridine nucleotide (DPN=NAD) and triphospho-pyridine nucleotide (TPN = NADP). The nicotinamide nucleotide coenzymes cue sometimes referred to as the pyridine nucleotide coenzymes. 

The metabolic function of the flavin coenzymes is as electron ceuriers in a wide Vciriety of oxidation emd reduction reactions central to till metabolic processes, including the mitochondritd electron tremsport chtiin. Unlike the nicotineimide nucleotide coenzymes (Section 8.4.1), which act as cosubstrates, leaving the cattdytic site of the enzyme at the end of the reaction, the flavin coenzymes remain bound to the enzyme throughout the catalytic cycle. 

The Emde reduction of apomorphine dimethyl ether methochloride affords the dihydromethine [ix] [69]. 

The cis relationship between the phenyl and methoxyl groups in CLIX has been confirmed by recent synthetic studies of Uyeo and his co-workers (86). Dihydroisotazettinol (in which the 3-hydroxyl and the phenyl are trans) was oxidized by manganese dioxide to CLIXa. Treatment of CLIXa with lithium aluminum hydride and cyclization of the resultant triol with dilute sulfuric acid gave an ether (CLIXb), the methi-odide of which afforded the neutral compound CLIXc upon Emde reduction. The synthesis of CLIXc started with CLIXd, the condensation product of piperonyl cyanide and methyl acrylate. Dieckmann... 

Hofmann elimination of nuciferine methiodide using sodium ethoxide led to the phenanthrene derivative (38), but use of the bulkier base potassium triethylcarbino-late afforded the optically active styrene (39). The dihydrophenanthrene (40) was obtained through Emde reduction of the starting methiodide salt using sodium amalgam in water. 

Although the ethylenic linkage may have suffered an alteration of position during the reductive process, the absorption of one mole of hydrogen by catalytic reduction (palladized charcoal) indicated that the double bond was still present ir methyldihydroneostrychnidine. The resulting dihydromethyldihydroneostrychnidine (m.p. 176-177°) is not identical but isomeric with the methyltetrahydrostrychnidine (m.p. 192-193°) from the Emde reduction. These two reductions were accomplished simultaneously when methylstrychnidinium chloride was reduced catalytically (two moles of hydrogen). 

A second Emde reduction on the quaternary salt of methylvomicine-I cleaved ring E, trimethylamine being liberated from the resulting product by a Hofmann degradation. 

Alternatively, ( peshawarine has been obtained from ( + )-rhoeadine methiodide through Emde reduction followed by acid hydrolysis which provided a racemic hemiacetal. Jones oxidation of this material furnished the secoberberine alkaloid as a racemate. ... 

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