Amides Thioamides

In catalytic hydrogenation, a compound is reduced with molecular hydrogen in the presence of a catalyst. This reaction has found appHcations in many areas of chemistry including the preparation of amines. Nitro, nitroso, hydroxylamino, azoxy, azo, and hydrazo compounds can all be reduced to amines by catalytic hydrogenation under the right conditions. Nitriles, amides, thioamides, and oximes can also be hydrogenated to give amines (1). Some examples of these reactions foUow ... 

Cyanopyridazines add ammonia, primary and secondary amines and hydroxylamine to give amidines or amidoximes. Substituted amides, thioamides and carboximidates can be also prepared. With hydrazine, 3-pyridazinylcarbohydrazide imide is formed and addition of methylmagnesium iodide with subsequent hydrolysis of the imine affords the corresponding pyridazinyl methyl ketone. 

Me3Si)2NH, Me3SiCl, Pyr, 20°, 5 min, 100% yield. ROH is a carbohydrate. Hexamethyldisilazane (HMDS) is one of the most common sily-lating agents and readily silylates alcohols, acids, amines, thiols, phenols, hydroxamic acids, amides, thioamides, sulfonamides, phosphoric amides, phosphites, hydrazines, and enolizable ketones. It works best in the presence of a catalyst such as X-NH-Y, where at least one of the group X or Y is electron-withdrawing. ... 

Keto amides (or thioamides) could participate in cyclocondensations by elimination of the amino or oxo (thioxo) function from the amide (thioamide) grouping according to conditions. The other synthons should behave reasonably predictably. The following examples illustrate some possibilities. 

Derivatives of amides, thioamides, sulfonamides, and related compounds... 

Comparison of the Barriers to Rotation of Amides, Thioamides, and Selenoamides... 

A proton NMR study by Mirek and Bogdanowicz-Szwed128 observed that the 5-proton was significantly deshielded in 3-amide, -thioamide, and -amidine derivatives, and this established the preferred conformation as 83. 

N-Acetylation.1 Amides, thioamides, ureas, and thioureas are N-acetylated at 25° by acetic acid in CH2CI2 in the presence of this reagent. It can serve as a catalyst, but stoichiometric amounts are required for high yields. 

Addition of isocyanates and isothiocyanates, followed by hydrolysis, yields amides, thioamides,274-277 or ureides of j8-ketoacids 82 and 83 are examples of typical intermediates in this reaction. 

Expectedly, chloroformiate introduces an ester group 34,38) whereas isocyanates, isothiocyanates and carbodiimides lead to the respective push-pull aminodiyne amides, thioamides and amidines (132-135) 34,37). 

The compound Ar2Bi(0)0Me, which was prepared via the reaction of ArsBi and 4-MeC6H4S02NClNa, has been reported to acylate amides, thioamides, ureas, and thioureas. The first step of the process is believed to be reaction of the Ar2Bi(0)0Me compound with acetic acid to replace the methoxide with acetate. ... 

Lanthanide shift reagents have been used to study dynamic NMR processes. One of the classic applications involves the study of rotational barriers of various amides " thioamides ", oximes " and amide oximes ". Lanthanide-induced shifts enabled the distinction of cis- and trans- or syn- and awri -isomers, and variable-temperature studies in the presence of the chelate were performed to determine the barrier to rotation. 

The following esters, amides (thioamides), and nitriles have been hydrolyzed (under the conditions indicated) to the corresponding carboxypyrazines (unless otherwise stated) as listed below. 

In a number of amides, thioamides, and related systems, rotation about the single bond is hindered, and distinct geometric isomers can be observed and even isolated. This type of geometric isomerism is referred to as atropisomerism and results from resonance contributions by the nitrogen atom that imparts significant double bond character to the system, thus slowing rotation. Such is the case for the thioamide aldose... 

From Rings with an Amino Group Adjacent to an Acid Amide, Thioamide, or Ester Group... 

I Adducts from Amides (Thioamides) and Acylating Reagents... 

Functional group substituents on N-l of 2-pyrazolin-5-ones (Table XXXVII) are acyl, sulfonyl and various carboxyl derivatives, such as carbalkoxy, amides, thioamides, hydrazides, thiohydrazides and amidines. The usual synthesis of these compounds is by the classical 2-pyrazolin-5-one synthesis, reaction of a /J-ketoester with a hydrazine. In these cases the hydrazines are special types such as hydrazide,... 

Benzoin, tetraphenylethanediol, hydrazobenzene and 1,2-diphenyl-1,2-ethanedione bishydrazone are oxidized by methyl bis(l-naphthyl)bismuthi-nate to benzil, benzophenone, azobenzene and diphenylacetylene, respectively [88CL2021] (Section 5.2.4). Amides, thioamides, ureas and thioureas are A-acylated in good yield with acetic acid in the presence of the bismuthi-nate at room temperature [90CL1651] (Scheme 3.11). 

Chloro- and methyl-substituted acetic and propionic acids Amide, thioamide, and amidine herbicides Amides Ureas... 

The reaction of V-cyanocarboximidamide with (chloromethylene)iniinium salts provides another important route to substituted 1,3,5-triazines.394,395 The (chloromethylene)iminium salts are prepared in situ from the corresponding amides, thioamides or dithiocarbamates and phosphoryl chloride, phosphorus pentachloride or phosgene (cf. Houben-Weyl, Vol. E5,... 

The barrier to rotation about the C—N bond in various NN-dimethyl-amides,-thioamides and -amidinium ions decrease in the order thioamides > amides amidinium ions. The values for the coupling constants of the A -methyl groups are related to the extent of the localization of the positive charge on the nitrogen atom. 

In addition to niiro compounds, nitroso, hydroxylaminot azoxy, azo and hydrazo compounds can also be reduced to amines. Nitriles, amides, thioamides, and oximes of both aldehydes and ketones can be hydrogenated to amines. 

General discussion of intra- and intermolecular interactions 3 van der Waals interactions 3 Coulombic interactions 5 Medium effects on conformational equilibria 5 Quantum mechanical interpretations of intramolecular interactions 7 Methods of study 8 Introduction 8 Nmr and esr spectroscopy 8 Microwave spectroscopy (MW) 12 Gas-phase electron diffraction (ED) 12 X-ray crystallographic methods 13 Circular-dichroism spectroscopy and optical rotation 14 Infrared and Raman spectroscopy 18 Supersonic molecular jet technique 20 Ultrasonic relaxation 22 Dipole moments and Kerr constants 22 Molecular mechanic calculations 23 Quantum mechanical calculations 25 Conformations with respect to rotation about sp —sp bonds 27 Carbon-carbon and carbon-silicon bonds 28 Carbon-nitrogen and carbon-phosphorus bonds 42 Carbon-oxygen and carbon-sulphur bonds 48 Conformations with respect to rotation about sp —sp bonds Alkenes and carbonyl derivatives 53 Aromatic and heteroaromatic compounds 60 Amides, thioamides and analogues 75 Conclusions 83 References 84... 

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