Reductive alkylations metal-ammonia reduction

The benzyl 1C methoxy group is then removed by metal-ammonia reduction. Alkylation with p-nitrophenethyl bromide would then give the intermediate 78. Reduction of the nitro group would thus afford verilopam (79). The same... 

As first demonstrated by Stork,78 the metal enolate formed by metal-ammonia reduction of a conjugated enone or a ketol acetate can be alkylated in liquid ammonia. The reductive alkylation reaction is synthetically useful since it permits alkylation of a ketone at the a-position other than the one at which thermodynamically controlled enolate salt formation occurs. Direct methyl-ation of 5a-androstan-17-ol-3-one occurs at C-264 whereas reductive methyl-... 

Metal ammonia reduction of 17a-ethynyl-19-nortestosterone, 52 Metal ammonia reductions and reductive alkylations, 43 Methanol-OD, 212... 

TABLE 6.3 Reductive Alkylation of Ammonia with 4-f-Butylcyclohexanone over Platinum Metals ... 

Table I. Reductive Alkylation of Anthracene, Naphthalene, and Biphenyl in Metal-Ammonia Solutions...

Dithioacetals can also be desulphurized under radical conditions using tributyltin hydride (TBTH) (equation 65) or by using metal-ammonia solutions (equation 66). Lithium aluminium hydride has also been used in some cases for reductive desulphurization. In a manner analogous to the preparation of dithioacetals, ketones can be transformed to diselenoacetals with aryl or alkyl selenol. These in turn have been reduced with Raney or Li-EtNH2 and under radical conditions with TBTH or... 

Reductive amination (Section 22.10) Reaction of ammonia or an amine with an aldehyde or a ketone in the presence of a reducing agent is an effective method for the preparation of primary, secondary, or tertiary amines. The reducing agent may be either hydrogen in the presence of a metal catalyst or sodium cyanoborohy-dride. R, R, and R" may be either alkyl or aryl. 

Borazine originally was obtained by the reaction of ammonia with diborane.1 Mixtures of lithium or sodium tetrahydro-borate with ammonium chloride also have been pyrolyzed to yield this product.2 More recently, the reduction of B,B, B"-trichloroborazine with alkali metal hydroborates has proved to be a convenient laboratory-scale method for the preparation of this compound.3-7 The procedure described herein is a variation of the last method as reported by Dahl and Schaeffer.7 This method is effective for the synthesis of iV-substituted alkyl- and arylborazines, i.e., compounds of the formula (HBNR)3 where R is CH3, C2H6, C6H , C6H5, p-C6H4CH3, or p-C6H4OCH3.5... 

Additionally, it was found that the double reductive alkylation of the 2,5-diester 66 could be achieved under Birch conditions (Li/NH3) to produce the 3-pyrroline 67. On the basis of a mechanistic postulate that such reductions do not involve transfer of a proton from ammonia, the authors discovered that the same reduction could be performed in THF (no ammonia) with lithium metal and catalytic amounts of naphthalene as an electron shuttle, thereby making this reaction more practicable on a large scale <00TL1327>. 

One final example worth mentioning is the reductive alkylation/arylation with lithium and alkyl/aryl halides in liquid ammonia. This is a two-step process in which negatively charged nanotubes are formed via electron transfer from the metal. This step is relatively easy and fast due to the CNTs electron sink properties, and it enables exfoliation of the tubes through electrostatic repulsion in the second stage, the alkyl/aryl halides react with the charged tubes to form a radical anion which can dissociate into the alkyl radical and the halide anion, with the former species undergoing addition to the CNT sidewalls [42]. 

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