Keto-imines

Tomic K, Jorg T, Marian CM (2005) Quantum chemical investigation of the electronic spectra of the keto, enol, and keto-imine tautomers of cytosine. J Phys Chem A 109 8410-8418... 

The benzoylphenylketene generated from 321 displayed a pronounced tendency to form chemospecific [2+4] Diels-Alder adducts with the C=N group of keto-imines. When compounds 328, derived from />-aminoacetophe-none and aromatic aldehydes, were reacted with a-diazo-/3-diketone 321, 2,3-dihydro-4//-l,3-oxazin-4-ones 329 were obtained via the addition of benzoylphenylketene to the C=N bond, and no formation of the corresponding C=0 adducts, 477-l,3-dioxin-4-ones, was observed (Equation 31) <2001J(P1)2266>. 

From a more traditional standpoint, 1,2-diaminobenzenes were condensed with a variety of 1,2-dielectrophiles ranging from a-keto esters (184 + 185- 186 <99H1213>) and 1,2-diketones (187 + 188 189 <99JA10438>) to a-keto imines (190 -i- 191 192... 

Acid Dissociation Constants and Formation Constants. Attempts to determine acid dissociation constants of bisacetylacetoneethylenediimine and bis-acetylacetone-m-phenylenediamine in 50 volume % dioxane-water were unsuccessful. The procedure used was successful when applied to bis (/ -diketones) (II). Likewise, attempts to determine formation constants of the tetradentate / -keto-imines were unsuccessful, apparently because of hydrolysis. 

Tropolone complexes (20) also undergo electrophilic substitution, but the numerous positions for reaction give rise to mixtures of products. The p-keto imine complexes (21) and (22)32 have been brominated successfully using )V-bromosuccinimide. 

Reductive carbonylation and alkylation of imines.3 This cobalt carbonyl catalyzes a reaction of imines with organoboranes and carbon monoxide that results in amides. / -Keto amides are obtained from a-keto imines by this reaction. 

Alternatively, reduction of the keto-imine (20) with sodium borohydride gave a mixture of two carbinols corresponding to N-demethylated (16) and (17). Irradiation of this mixture produced norushinsunine together with a little noroliveroline. Photolysis of the alcohol (21) gave rise to the oxoaporphine liriodenine (22).21 Synthetic routes to those aporphines that incorporate a hydroxyl group at C-7 that is trans to the proton at C-6a are already known.22 23 A novel synthesis of aporphines via 3-phenylphenethylamines has been developed, and is described in Scheme 1. The aporphine (23) and related species were then synthesized by a modified route.24... 

Alkylation of a-nitro keto imines. The key step in a conversion of cyclic a-nitro ketones to cyclic 3-substituted 1-nitroalkenes (4) involves alkylation of the dianion of an a-nitro imine (2) or hydrazone. The dianions are easily generated,... 

The oxazaborolidine-catalyzed reduction of 1,2-diketones (Equation (258)),1116-1120 1,2-keto-imines (Equation (259)),1121-1123 and 1,2-diimines (Equation (260))1124 provided optically active 1,2-diols, amino alcohols, and 1,2-diamines with both high enantiomeric and diastereomeric excess. The method can be also effective for (3- and y-analogs. 

Within the field of chiral ion pair catalysis only aldimines and keto-imines had been activated so far. However, we have recently been successful in the activation of both the electrophile, as well as the nucleophile in a new double Brpnsted acid catalyzed reaction. 

Later, Arcadi showed that /J-keto-imines react with alkynes intramolecularly to give pyrroles. The intermolecular animation with aniliaes was later developed by Hayashi and Tanaka using a cationic Au(I) catalyst to form imines (equation 27). More recently, Arcadi etal. developed an intramolecular version for the cyclization of o-alkynylanilines to form indoles (equation 28) and Li reported a double intra- and intermolecular hydroamination to obtain A-vinylindoles. " O-Substituted hydroxylamines can also undergo this type of transformation to dihydroisoxazole derivatives. " " Tandem sequences that involve a first alkyne-hydroamination step with anilines have been recently developed " " and are similar to the previonsly discnssed additions with phenols that access isoflavone skeletons. 

Benzophenone with tertiary amines has been used to polymerize bis 2-[2-(methacryloyloxy)ethoxy]ethyl phthtilate and triethylene glycol dimethacrylate in bulk, while mixtures of ZnO and l,8-diamino-3,6-diazaoctane have been used to emulsion-polymerize styrene. An internal keto-imine compound,... 

This synthesis is an example of chelate exchange, the advantages of which are noted later. Attempts to prepare bis(3-phenylimino-l-phenyl-l-butanonato)copper-(II) by direct combination of the /3-keto imine (/3-imino ketone) and ammoniacal copper(II) nitrate have not been successful. However, the compound can be obtained from reaction of the jS-keto imine and bis(4-imino-2-pentanonato)-copper(II) [bis(4-amino-3-penten-2-onato)copper(II)] prepared by the method of Holtzclaw, Collman, and Alire. ... 

Metal derivatives of S-keto imines ( 8-imino ketones), synthesis 13... 

METAL DERIVATIVES OF g-KETO IMINES (5-IMINO KETONES)... 

The methods of preparation and purification of metal derivatives of 1,3-diketones have been described in a previous volume. Because of the interest in the structure " and reactions of metal derivatives of /3-keto imines, RC0CH2C(=NR )R", it is desirable to consider the methods of preparation of these compounds. Inasmuch as /3-keto imines are closely related to 1,3-diketones and to salicylaldimines, o-HOC6H4CH==NR, the methods of preparation show similarities. Although this review is concerned principally with /3-keto imines, some comparisons with 1,3-diketones and salicylaldimines are made. 

Direct Reaction of -Keto Imines with Metal Salts. 

In Aqueous Solution. The direct reaction between a d-keto imine and a salt in water is limited by the slight solubility of most d keto imines in water and is essentially... 

Direct reaction is commonly effected in a mixed-solvent system, frequently by mixing an ethanolic solution of the jS-keto imine with an aqueous solution of the metal salt. An ammoniacal metal salt solution can be used to prevent hydrolysis and to shift the chelation equilibrium (see synthesis 60). This practice can be very effective, but it has the disadvantage of adding extraneous ions furthermore, the high concentration of ammonia may result in an undesired amine exchange. ... 

In Nonaqueous Solution. The use of a nonaqueous solvent in which both the metal salt and the /3-keto imine are soluble eliminates many of the problems of contamination due to hydrolysis, the presence of extraneous ions, and unfavorable equilibria. Halides such as ECU, AICI3, SiCU, GeCU, ZrCU, ThCU, NbCU, and TaCU, which are soluble in an inactive organic solvent, have been used in the reaction with 1,3-diketones but apparently not with /3-keto imines. However, the reaction of metal acetates with /3-keto imines has been effected successfully in dioxane, ethanol, - or methanol. ... 

Reaction of a g-Keto Imine with a Metal Hydroxide. 

This procedure consists of refluxing an acetone solution of the /3-keto imine with a freshly prepared metal hydroxide. The product precipitates from solution upon cooling or is obtained by dilution of the acetone solution with water. The method has been used to prepare the copper(II), nickel(II), and cobalt(II) derivatives of a variety of /3-keto imines, - but attempts to prepare zinc and cadmium derivatives were not successful. The advantages of this procedure have been described previously. On occasion, the chelate compound may precipitate during the reaction... 

Direct Combination of a 1,3-Diketone, an Amine, and a Metal Ion. Direct combination is a potentially useful reaction, and it has been used to prepare metal-salicylaldimine compounds. The procedure consists of mixing (and refluxing if necessary) a stoichiometric mixture of salicylaldehyde with an amine, a metal ion, and a base in dilute aqueous methanol. This procedure has not been applied commonly to the preparation of metal derivatives of jS-keto imines, although the preparation of 4,4 -(ethylene-dinitrilo)di-2-pentanonatocopper(II) from 2,4-pentanedi-one (acetylacetone), ethylenediamine, and copper has been described. Attempts to effect condensation of 1,1,1,5,5,5-hexafluoro-2,4-pentanedione (hexafluoroacetylacetone) and ethylenediamine by direct combination of the reactants in the presence of copper(II) acetate were imsuccessful. ... 

Amine Exchange Reaction of a g-Keto Imine with an Amine in the Presence of a Metal Ion... 

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