Imidates, with ammonia

PINNER REACTION. Formation of imino esters (alkyl imidates) by addition of dry hydrogen chloride to a mixture of a nitrile and an alcohol. Treatment of alkyl imidates with ammonia or primary or secondary amines affords amidines. while treatment with alcohols yields ortho-esters. 

Conversion of acid derivatives into amines with the loss of the carbonyl group can be done in i.-ious ways. In Chapter 40 we recommended either the Curtius rearrangement or the Hofmann tejradation (p. 1073). The Hofmann degradation is easier starting with an ester. We convert into . imide with ammonia and treat with bromine in basic solution. The N-bromo derivative forms a afcene by a-elimination that rearranges to an isocyanate. 

To minimize the formation of fuhninating silver, these complexes should not be prepared from strongly basic suspensions of silver oxide. Highly explosive fuhninating silver, beheved to consist of either silver nitride or silver imide, may detonate spontaneously when silver oxide is heated with ammonia or when alkaline solutions of a silver—amine complex are stored. Addition of appropriate amounts of HCl to a solution of fuhninating silver renders it harmless. Stable silver complexes are also formed from many ahphatic and aromatic amines, eg, ethylamine, aniline, and pyridine. 

The oxygen is ehemisorbed on the eatalyst. This then reaets with ammonia to produee a ehemisorbed imide radieal. The imide reaets with a moleeular oxygen to yield nitrie oxide. 

When the reaction of S2CI2 with ammonia is carried out in a polar solvent, e.g., DMF, the hydrolysis of the reaction mixture with aqueous HCl produces a mixture of the cyclic sulfur imides S7NH, 1,3-, 1,4- and 1,5-S6(NH)2 and 1,3,5- and 1,3,6-S5(NH)3, which can be separated by chromatography on silica gel using CS2 as eluant (Section 6.2.1). °... 

Thionyl imide, HNSO, is a thermally unstable gas, which polymerizes readily. It can be prepared by the reaction of thionyl chloride with ammonia in the gas phase. Organic derivatives RNSO have higher thermal stability, especially when R = Ar. The typical synthesis involves the reaction of a primary amine or, preferably, a silylated amine with thionyl chloride. A recent example is the preparation of FcNSO (Fc = ferrocenyl) shown in Eq. 9.8. In common with other thionylimines, FcNSO readily undergoes SO2 elimination in the presence of a base, e.g., KO Bu, to give the corresponding sulfur diimide FcNSNFc. 

As in 10-55 hydrazides and hydroxamic acids can be prepared from carboxylic esters, with hydrazine and hydroxylamine, respectively. Both hydrazine and hydroxylamine react more rapidly than ammonia or primary amines (the alpha effect, p. 445). Imidates, RC(=NH)OR, give amidines, RC(=NH)NH2. Lactones, when treated with ammonia or primary amines, give lactams. Lactams are also produced from y- and 5-amino esters in an internal example of this reaction. 

Figure 2.5 Dynamics of oxygen chemisorption at Cu(110) and Mg(0001) surfaces based on XPS and HREELS leading to oxidation of ammonia and imide chemisorbed species. The reactive oxygen is a transient state Cr(s). With ammonia-rich mixture Pathway 2 is dominant whereas for oxygen-rich mixtures Pathway 1 dominates at 295 K.

Naphthalic acid imide 69 is obtained through air oxidation of acenaphthene 72 with vanadium peroxide as a catalyst. The intermediate, naphthalic anhydride 73, is subsequently reacted with ammonia ... 

The cyclic sulfur imides S NH and 1,3-, 1,4-, and l,5-S(j(NH)2 are obtained by acid hydrolysis of the deep blue intermediate formed from the reaction of SjClj with ammonia in polar solvents, e.g. DMF or by the reaction of sodium azide with elemental sulfur in HMPA The blue chromophore formed in both these reactions is S4N and it has therefore been suggested that this anion is involved in equilibria with cyclic sulfur-nitrogen anions which are the precursors of the imides... 

Piroxicam Piroxicam, 1,1 -dioxid-4-hydroxy-2-methyl-iV-2-pyradyl-2//-1,2-benzothiazine-3-carboxamide (3.2.78), is synthesized from saccharin (3.2.70). Two methods for saccharin synthesis are described. It usually comes from toluene, which is sulfonated by chlorosulfonic acid, forming isomeric 4- and 2-toluenesulfonyl chlorides. The isomeric products are separated by freezing (chilling). The liquid part, 2-toluenesulfonyl chloride (3.2.68) is separated from the crystallized 4-toluenesulfochloride and reacted with ammonia, giving 2-toluenesul-fonylamide (3.2.69). Oxidation of the product with sodium permanganate or chromium (VI) oxide in sulfuric acid gives saccharin—o-sulfobenzoic acid imide (3.2.70) [123-126]. 

A commercial NSAID and some of its analogues that depend on an enolized heterocyclic ring for an acidic proton are considered in more detail later in this chapter. The preparation of a simplihed example starts by conversion of homophtha-lic acid (56-1) with ammonia to its imide (56-2). Reaction of that product with pam-chlorophenylisocyanate (56-3) in the presence of triethylamine results in the addition... 

The standard preparation of these cyclic sulfur imides, with the exception of cyclo-S4N4H4, involves the reaction of S2CI2 with gaseous ammonia in a polar solvent, e.g. DMF, at —10°C followed by hydrolysis with cold, dilute HCl... 

The preparation of N-alkyl imides by exchange reaction of an imide with an alkyl amine was documented [104] well before the application of this chemistry to the preparation of polyimides [105], see Scheme 30. Although no experimental details are provided, the initial reaction of pyromellitimide with p,p-methylene dianiline in NMP takes place at reflux temperatures to apparently yield a poly(amic amide). Subsequent heating of this intermediate at elevated temperatures ( 300 °C) provides the desired polyimide with evolution of ammonia. The final polyimide is quoted to be thermally and chemically stable, however, no mechanical properties are given. 

This reaction, similar in scope and mechanism8S2 to 0-52, can be carried out with ammonia or primary or secondary amines.853 However, ammonia and primary amines can also give imides, in which two acyl groups are attached to the nitrogen. This is especially easy with cyclic anhydrides, which produce cyclic imides.854... 

Pyrylium cations form pyridines with ammonia and pyridinium salts with primary amines (B-82MI 505-02). For example, 2,4,6-triphenylpyrylium cation (261 Z=0) yields 2,4,6-triphenylpyridine with ammonia, the corresponding 1-methylpyridinium salt with methylamine, and pyridine 1-arylimines with phenylhydrazine. Xanthylium ions (210), where ring opening cannot readily occur, form adducts (262) with ammonia, amines, amides, ureas, sulfonamides and imides. Similar adducts (e.g. 263) are formed by benzo[( ]pyrylium ions. 

Scheme 6 Cyclic Imide Formation with Ammonia 161 ...

The synthesis of a dipeptide dihydrothiazole by way of an imidate is shown in Scheme 13.[521 The Boc-protected amino acid 37 (in this case Val) was converted into the primary amide 38 by the mixed anhydride coupling with ammonia. The amide was then directly converted into the imidate 39 using triethyloxonium hexafluorophosphate which was subsequently condensed with H-Cys-OEt to provide the dihydrothiazole 40. 

The metal amides and imides are important in the nitrogen system. The amides of the active metals are produced by (1) reaction of the metal with NIL, (2) reaction of the metal hydride with NIL, (3) reaction of the metal nitride with ammonia, (4) reaction with another amide, as... 

The cyclic anhydride of butanedioic acid reacts with ammonia, as may be expected for a typical anhydride but the product, when strongly heated, forms a cyclic imide (butanimide) ... 

W. Traube described the formation of what he called sulphimide, along with ammonia and imidosulphonic acid, when sulphamide is heated at 200°-210°. The solid product is treated with water, the soln. mixed with silver nitrate, and the precipitated silver sulphimide, purified by recrystallization, is decomposed with dil. hydrochloric acid. The aq. soln. decomposes when the attempt is made to isolate the solid, for when the soln. is evaporated below 40°, only ammonium hydrosulphate remains. A. Hantzsch and A. Holl found the soln. in ethyl acetate has properties in accord with the trimolecular formula sulphucyl trumide, or trisulphimide, (S02.NH)3—e.g. ebulliscopic determinations of the mol. wt. and the electrical conductivities of the aq. soln. of trisulphimide and its salts. They were able to isolate a crystalline solid by crystallization from ethyl alcohol which they considered to be trisulphimide itself. A. Hantzsch and B. C. Stuer, however, showed that the alleged compound is extremely unstable, and that the soln. obtained by W. Traube, and the solid obtained by A. Hantzsch and A. Holl, was really sulphuryl imidodiamide, only indications of the transient formation of trisulphimide in non-aqueous solvents were obtained. Trisulphimide acts as an acid, and a few salts have been reported. A. Hantzsch and B. C. Stuer consider that the compound has tautomeric forms—a true imide and an acid ... 

The oxygen is chemisorbed on the catalyst. This then reacts with ammonia to produce a chemisorbed imide radical. The imide reacts with a molecular oxygen to yield nitric oxide. 

It must also be pointed out that other basic materials have been synthesized which present no surface oxygens and hydroxyls, but other types of active sites whose exact nature remains controversial. These type of solids are, for example, impregnated imides and nitrides on zeolites and alumina, amorphous oxynitrides obtained by treatment with ammonia or aluminium orthophosphate, zirconium phosphate, aluminium vanadate or galloaluminophosphate, and KF supported on alumina/1,3,41 One of the main advantages of these solids with respect to basic oxides is their resistance to carbon dioxide or water. 

Step-by-step replacement of the hydrogen atoms in ammonia with metal atoms according to (34) or (35) leads to the amides MNH2, the imides M2NH, and the nitrides M3N. The alkali and alkaline-earth amides can be obtained from the reaction of the hot metals with ammonia. 

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