Ketones reductions, carbon-nitrogen

The electrochemical reduction of various bicyclic a-amino ketones such as quinolizidinone (n = 2) (Scheme 159) can involve a cleavage of the carbon-nitrogen bond giving a ring enlargement [275, 276]. 

Ketones containing sulfur or nitrogen atoms bound to a-carbons suffer carbon-sulfur or carbon-nitrogen bond cleavage under the conditions of the Clemmensen reduction [159, 864 (p. 118). A ketosulfone was reduced to a sulfone-alcohol with zinc in refluxing 80% acetic acid in 70% yield [920]. 

Many aldehydes (RCHO) and ketones (R2CO) are converted into amines by reductive amination reduction in the presence of ammonia. Reduction can be accomplished catalytically or by use of sodium cyanohydridoboratc, NaBHjCN. Reaction involves reduction of an intermediate compound (an imine RCH NH or R2C NH) that contains a carbon-nitrogen double bond. 

In 1999 [22] and 2001 [23], Matsumura and co-workers reported the first examples of stereoselective hydrosilylation with HSiCla and (5)-proline derivatives as effective activators. These works can be considered as milestones for the asymmetric reduction of ketones and imines using HSiCla as reducing agent and paved the road to the synthesis of other related systems. Since then, considerable efforts have been devoted to the development of efficient catalysts for the reduction of carbon-nitrogen double bonds, and remarkable progress has been made. 

Buchanan et al. [167] discuss the measurement of bulk carbon, nitrogen, and hydrogen isotope values of 18 MDMA samples synthesized using aliquots of the same precursor (piperonyl methyl ketone, PMK) but utilizing three different reductive amination methods. The results indicated that the hydrogen isotope data was essential for the discrimination of samples based on synthetic pathways. 

Iron salts have recently attracted considerable attention as inexpensive and environmentally friendly agents in a wide range of selective processes in organic synthesis. Over the past decade, FeCls 6H2O has shown to be an effective catalyst in the formation of carbon-carbon or carbon-nitrogen bonds, in intramolecular Friedel-Craft reactions and in the reduction of ketones or allylic alcohols. ... 

In contrast to the numerous known asymmetric ketone reductions, only limited success has been achieved in the reduction of ketimines. This is due to the low elec-trophilicity of the imine carbon and rapid equilibrium between the E and Z isomers [80]. In addition, most chiral Lewis acids, including OABs, are trapped by the basic nitrogen atoms of imines and/or product amines, leading to a decreased catalytic effect. 

A mixture of N-phenyl-p-phenylenediamine, acetone, and 20%-molybdenum sulfide-on-alumina catalyst (Girdler T-318) hydrogenated 5.5 hrs. at 180-190°/ 500-700 p.s.i.g. -V N-isopropyl-N -phenyl-p-phenylenediamine. Y ca. 100%.— Metal sulfides often will be the catalysts of choice for reductive alkylations because of their extreme resistance to poisoning, and their ability to minimize nuclear hydrogenation, carbon-nitrogen cleavage, and, in most cases, ketone reduction. F. e. and catalysts s. F. S. Dovell and H. Greenfield, J. Org. Chem. 29, 1265 (1964). 

Ketones can be reduced directly to alkanes by the Wolff-Kishner reduction. In this reduction, the ketone is converted to the hydrazone, which is treated in situ with sodium hydroxide. An internal redox reaction occurs in which the carbon is reduced and the hydrazine is oxidized to nitrogen. The best experimental conditions include the use of NaOH and ediylene glycol as solvent to carry out the reduction. 

The reduction of aldehydes and ketones to alkanes. Condensation of the carbonyl compound with hydrazine forms the hydrazone, and treatment with base induces the reduction of the carbon coupled with oxidation of the hydrazine to gaseous nitrogen, to yield the corresponding alkane. 

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