Imines azines

Thiiranimine 1,1-dioxide has not been isolated however, it is formed in situ when ketene is dissolved in liquid S02 at — 78 °C. It can react with imines, azines, and tosyl isocyanate (Scheme 56) <76JOC3925>. 

Other groups that react with chloromethyleneiminium salts include hydroxylamines, hydrazines, oximes, imines, azines, anhydrides, imides and ketene O-alkyl-O -silyl acetal derivatives however, reactions with these compounds have been relatively infrequent. 

The equilibrating mixture of ethylidyne complex 22 and vinylidene complex 23 have been found to give a variety of new reactions with imines, azines, and carbodiimides (see Scheme VUI) [5]. Although the products of the reactions described below are... 

Benzophenone Process. Benzophenone, (CgH5 )2C=0, reacts with ammonia to form diphenylmethanimine, (CgHg )2C=NH. In the presence of copper catalysts, this is oxidized with oxygen to benzophenone azine, (CgHg )2C=N—N=C(CgHg The formation of the imine and its... 

Carbon—nitrogen double bonds in imines, hydrazones, oximes, nitrones, azines, and substituted diazomethanes can be cleaved, yielding mainly ketones, aldehydes and/or carboxyHc acids. Ozonation of acetylene gives primarily glyoxal. With substituted compounds, carboxyHc acids and dicarbonyl compounds are obtained for instance, stearoHc acid yields mainly azelaic acid, and a smaH amount of 9,10-diketostearic acid. 

Reactions of azines and imines (including criss-cross cycloaddition) 76S349... 

A simple preparative route to the previously unknown lH-3-pyrazolines via azomethine imines was developed. Olefins of the type R cH=CHR react with hexafiuoroacetone azine to give azomethine mines, which undergo a sequence of prototropic shifts to form 17/-3-pyrazolines [196, 202], On heating, the latter are transformed into 3-trifluoromethylpyrazoles [196, 206] and, on treatment with bases, into 1,2,5,6-tetrahydropynmidines [206] (equation 45)... 

An unusual 1,4-migration of a trifluoromethyl group was observed when azomethine imines were synthesized from hexafluoroacetone azine and alkoxy-acetylenes The rearrangement, which occurs at temperatures as low as 0 "C, results in the formation of A-(perfluoro-ferf-butyl)pyrazoles [207] (equation 46)... 

Sokolov and Aksinenko described a series of transformations of 2-aminoazoles and azines with A-ethoxycarbonyl-hexafluoroacetone imine <2003IZV2053>. In this research, these authors found that 2-aminothiazoline 234 can be transformed to the ring-closed compound 235 in good yield (71%). 

Terminal alkynes readily react with coordinatively unsaturated transition metal complexes to yield vinylidene complexes. If the vinylidene complex is sufficiently electrophilic, nucleophiles such as amides, alcohols or water can add to the a-carbon atom to yield heteroatom-substituted carbene complexes (Figure 2.10) [129 -135]. If the nucleophile is bound to the alkyne, intramolecular addition to the intermediate vinylidene will lead to the formation of heterocyclic carbene complexes [136-141]. Vinylidene complexes can further undergo [2 -i- 2] cycloadditions with imines, forming azetidin-2-ylidene complexes [142,143]. Cycloaddition to azines leads to the formation of pyrazolidin-3-ylidene complexes [143] (Table 2.7). 

Alkyl-3-formylcarbazoles form-arylhydrazones " and azines or hydrazones with hydrazine. 9-Ethyl-3-formylcarbazole gives Schiflf bases with arylamines. Variously substituted 3-formylcarbazoles condense with aminoacetal, " and the resulting imines are easily reduced catalytically or with sodium borohydride. Anils from... 

Table 11 summarizes the main results on the tautomerism of mono-hydroxy-, -mercapto-, -amino- and -methyl-azines and their benzo derivatives, in water. At first sight the equilibrium between 2-hydroxypyridine (71) and pyridin-2-one (72) is one between a benzenoid and a non-benzenoid molecule respectively (71a 72a). However, the pyridinone evidently has a continuous cyclic p- orbital system, containing six it- electrons, the usual aromatic count, if the carbonyl group contributes none. This assumption implies the formula (72b), from which by redistribution of electrons we arrive at (72c), which has the same benzenoid system as (71a). Further canonical forms (71b, 71c) can be drawn of (71) which correspond to the non-benzenoid forms of (72). The elusive property of aromaticity is therefore possessed by both tautomers, although not necessarily by both equally. When the carbonyl oxygen of (72) is replaced by less electronegative atoms, as in the imine tautomers of amino heterocycles, or the methylene tautomers of methyl derivatives, the tendency towards polarization in forms corresponding to (72b) and (72c) is considerably less, and the amino and methyl tautomers are therefore favoured in most instances. 

Ethylenimines or aziridines [lb] can be considered cyclic imines and are only briefly covered in Section 5. The preparation of heterocyclic imine systems, semicarbazones, hydrazones, azines, and oximes, is omitted from this chapter. The synthesis of carbodiimides is presented in Chapter 9. 

The acid-catalyzed cyclization of the azine 114 gave 1,2,3,4-tetrahydro-indazolo [3,2-b]8,9,10,l l-tetrahydroquinazol-7-imine (119), which was also obtained by cyclization of 2-cyanocyclohexanone with 3-amino-4,5,6,7-tetrahydroindazole (120) [63CI(M)709]. 

The azomethine imine 145 from isobutylene and hexafluoroacetone azine, with DMAD, leads to a stable 1 1 adduct (146) in 90% yield.132,133... 

Addition and cyclization reactions of imines, catalysed by IS r0 ns led acids, have been reviewed, including examples in water solvent and enantioselective cases.65 Another review examines stereoselective nucleophilic additions to the C=N bond of aromatic azines (60 references).66 (g)... 

Few 7r-bonded imine complexes have been prepared and investigated structurally. The only complexes of nonbridging 7r-bonded C=N investigated structurally are a substituted ketenimine complex (XLIV), an iminium complex (XLV), and a complex of the azine [(CF3)2C=N—)2 (XLVI) (see Table I). 

The azine complex (XLVI), formed by the reaction of bis(trifluoro-methyl) diazomethane with Pt(0) is a rather simple imine complex. The feature of note in this complex is angle y that represents one of the greatest observed deviations from planarity (7 = 127°). 

Azine approach. Examples of this heterocyclic ring system have been prepared from 3,4-dihydroisoquinoline azomethine imines (706) and sulfenes by 1,3-dipolar cycloaddition reactions. The products are l,5,6,10b-tetrahydro-3H-[l,2,3]thiadiazolo[4,3-a]isoquinoline 2,2-dioxide derivatives (707) (75JOC2260). 

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