Alkylation reactions reductive

Method 3. Reductive alkylation reaction of an amine or ammonia and hydrogen with an aldehyde or ketone over a hydrogenation catalyst. 

H NMR, 4, 1042 ionization potentials, 4, 1046 synthesis, 4, 1066 UV spectra, 4, 1044 Selenolo[2,3 -cjthiophenes H NMR, 4, 1042 synthesis, 4, 1067 UV spectra, 4, 1044 Selenolo[3,2-6]thiophenes dipole moments, 4, 1049 H NMR, 4, 1042 ionization potentials, 4, 1046 synthesis, 4, 1066 UV spectra, 4, 1044 Selenolo[3,4-6]thiophenes synthesis, 4, 1067 Selenolo[3,4-c]thiophenes addition reactions, 4, 1062 synthesis, 4, 1076 Selenomethionine applications, 4, 970 Selenophene, 3-acetamido-reactions, 4, 953 Selenophene, 2-acetyl-mercuration, 4, 946 nitration, 4, 947 Selenophene, 2-alkyl-reactions, 4, 45 synthesis, 4, 135, 967 Selenophene, 3-alkyl-synthesis, 4, 135, 967 Selenophene, 3-aryl-synthesis, 4, 963 Selenophene, 2-benzyl-reactivity, 4, 946 Selenophene, 2-benzyl-5-ethyl-reduction, 4, 950... 

An Index to types of reactions, e.g. alkylations, stereoselective reductions, cyclizations etc. and... 

Tabushi and Fujiyoshi have prepared alkylated cyclam derivatives for the purpose of suspending these systems from a polymer backbone. They have utilized a malonic ester alkylation reaction followed by cyclization and reduction to accomplish this end. ... 

Contents Introduction and Principles. - The Reaction of Dichlorocarbene With Olefins. - Reactions of Dichlorocarbene With Non-Olefinic Substrates. -Dibromocarbene and Other Carbenes. - Synthesis of Ethers. - Synthesis of Esters. - Reactions of Cyanide Ion. - Reactions of Superoxide Ions. - Reactions of Other Nucleophiles. - Alkylation Reactions. - Oxidation Reactions. - Reduction Techniques. - Preparation and Reactions of Sulfur Containing Substrates. -Ylids. - Altered Reactivity. - Addendum Recent Developments in Phase Transfer Catalysis. 

As first demonstrated by Stork,the metal enolate formed by metal-ammoni reduction of a conjugated enone or a ketol acetate can be alkylated in liquic ammonia. The reductive alkylation reaction is synthetically useful since ii permits alkylation of a ketone at the a-position other than the one at whicf thermodynamically controlled enolate salt formation occurs. Direct methyl-ation of 5a-androstan-17-ol-3-one occurs at C-2 whereas reductive methyl-... 

Rearrangement of a,/B-epoxy ketones to ftdicarbonyl isomers, 307 Reductive alkylation, 97 Reductive cleavage of halo ethers, 264 Reductive degradation of 19-substitutional steroids, 277, 278 Reformatsky reaction, 139 Removal of the C-10 substituent in steroids. 272... 

The reductive alkylation reaction under Clarke-Eschweiler conditions has been shown to proceed through an iminium intermediate (142). 

Besides acylation and alkylation reactions, typical carbonyl reactions, such as reduction and substitution, are known. Thus, the oxo group in position 3 of 8 is attacked by sodium cyanide, resulting in the cyanohydrin in 55% yield. Subsequent dehydration with p-toluene-sulfonic acid and acetylation in position 5 gives 1-benzothiepin 12.90... 

Aldehydes and ketones have been converted to sulfides by treatment with thiols and pyridine-borane, RCOR -I- R"SH —+ RR CHSR", in a reductive alkylation reaction, analogous to 16-6. 

Later work examined substituent effects on kinetically controlled alkylations [68, 69] (Scheme 32). Substitution at the 5-position is well tolerated in these reactions. Reductive lithiation of a series of 4-phenylthio-l,3-dioxanes and quenching of the axial alkyllithium intermediate with dimethyl sulfate provided the flzzfz -l,3-diols in good yield, with essentially complete selectivity. 

A combination of Friedel-Crafts alkylation and reduction can be achieved using InCl3 and chlorodimethylsilane. The Lewis acid presumably promotes both the Friedel-Craft reaction and the subsequent reduction.179... 

The anionic intermediates formed in Birch reductions can be used in tandem alkylation reactions. 

The UV-Vis spectral detection of an intermediate in the catalytic reductive alkylation reaction provides only circumstantial evidence of the quinone methide species. If the bioreductive alkylating agent has a 13C label at the methide center, then a 13C-NMR could provide chemical shift evidence of the methide intermediate. Although this concept is simple, the synthesis of such 13C-labeled materials may not be trivial. We carried out the synthesis of the 13C-labeled prekinamycin shown in Scheme 7.5 and prepared its quinone methide by catalytic reduction in an N2 glove box. An enriched 13C-NMR spectrum of this reaction mixture was obtained within 100 min of the catalytic reduction (the time of the peak intermediate concentration in Fig. 7.2). This spectrum clearly shows the chemical shift associated with the quinone methide along with those of decomposition products (Fig. 7.3). 

The above studies show that dithionite reduction of mitosenes results in the formation of lOa-sulfite esters as well as sulfonates. The presence of the excellent sulfite-leaving group at the mitosene 1 Oa-position suggests that alkylation reactions at this position could still occur. The subsequent sulfite to sulfonate rearrangement results in loss of alkylation capability by this position. 

Method B involves the preparation of precursor of 2-alkyl-l-benzo-pyrylium salts, as shown in Scheme ll.50 2-Alkylbenzopyrylium salts have been prepared by condensation of salicylaldehyde with appropriate ketone in acetic acid or by alkylation or reduction of coumarin or chromone derivatives. Reaction of 2-alkylbenzopyrylium salts with salicylaldehyde gives directly a spirodibenzopyran or 2-vinynologue benzopyrylium salt 17 which then can be converted into the spirodibenzopyran by piperidine or pyridine. 

The reductive alkylation reaction occurring during the hydrogenation of nitrobenzene in a 1-hexanol solvent is not between the aniline formed and the 1-hexanol but is between 1-hexanol and a surface species retained by the catalyst. This surface species is not formed during the aniline 1-hexanol reaction. There is also inhibition of the reaction between aniline and 1-hexanol. 

The cyanomethylation of nitroarenes followed by alkylation and reductive cyclization yields indoles (see Chapter 9, which discusses the VNS reactions) (Eq. 10.56).74... 

In recent years, the importance of aliphatic nitro compounds has greatly increased, due to the discovery of new selective transformations. These topics are discussed in the following chapters Stereoselective Henry reaction (chapter 3.3), Asymmetric Micheal additions (chapter 4.4), use of nitroalkenes as heterodienes in tandem [4+2]/[3+2] cycloadditions (chapter 8) and radical denitration (chapter 7.2). These reactions discovered in recent years constitute important tools in organic synthesis. They are discussed in more detail than the conventional reactions such as the Nef reaction, reduction to amines, synthesis of nitro sugars, alkylation and acylation (chapter 5). Concerning aromatic nitro chemistry, the preparation of substituted aromatic compounds via the SNAr reaction and nucleophilic aromatic substitution of hydrogen (VNS) are discussed (chapter 9). Preparation of heterocycles such as indoles, are covered (chapter 10). 

Allyl halides, reduction reactions, 31 Aluminum chloride reagent/catalyst alkyl halide reduction, 30-31 secondary alkyl alcohol reduction, 14-15... 

Radical chemistry has seen tremendous progress in the past two decades and can now be considered as an eminent sub discipline in synthetic organic chemistry [1-6]. Diastereoselective radical chemistry is well established and many examples of enantioselective radical reactions have appeared in the recent literature. For reviews on diastereoselective radical chemistry see [7-11] for reviews on enantioselective radical chemistry see [12-16] and for reviews on conjugate additions, see [17,18]. This review will detail different ways to introduce asymmetry during a radical reaction. These transformations can be broadly classified into atom transfer reactions, reductive alkylations, fragmentations, addition and trapping experiments, and electron transfer reactions. 

The catalysed two-phase alkylation of carboxamides has the advantages of speed and simplicity over the traditional procedures and provides a valuable route to secondary and tertiary amines by hydrolysis or reduction of the amides, respectively. The procedure appears to be limited, however, to reactions with primary haloalkanes and dialkyl sulphates, as secondary haloalkanes are totally unreactive [6, 7]. The use of iodoalkanes should be avoided, on account of the inhibiting effect of the released iodide ion on the catalyst. Also, the A-alkylation reaction is generally susceptible to steric effects, as seen by the low yields in the A -cthylation of (V-/-butylacetamide and of A-ethylpivalamide [6]. However, the low steric demand of the formyl group permits A,A-dialkylation and it is possible to obtain, after hydrolysis in 60% ethanolic sulphuric acid, the secondary amines having one (or, in some cases, two) bulky substituent(s) [7]. 

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