Ketones enamines

The preparation of enamine ketones by addition of a,jS-unsaturated ketones to enamines is described in Chapter 4. 

A process for the preparation of functionalized pyridines from diacetylene and the ethyl ester of /3-aminocrotonic acid and acetylacetonimine (72ZOR1328 75DIS) has been described. Owing to the lower nucleophilicity of nitrogen in the initial enamine esters and enamine ketone, the reaction with diacetylene occurs in the presence of sodium metal (80°C, dioxane, 3 h, yield of up to 20%). 

An interesting synthetic approach to cyclic enamine ketones is provided by waste-free and quantitative solid-state reaction of the anilines 236 with cyclic 1,3-diketones such as 332 or enolized 334 (Scheme 52). The enamine ketones 333c-h are quantitatively obtained in the solid state by milling at room temperature. The melt reaction (80 °C) for 333a is not quantitative, but 333b arises with 100% yield from the melt reaction [10]. All of the solid-state reactions give 100% yield, as usual. 

Anodic oxidation of enamine ketones or esters in CH30H-NaC104 at a graphite anode gives substituted pyrroles in 15-45% yield.101 Formation of the symmetrically substituted pyrroles 47 indicated radical dimerization of radical-cations formed as primary products from 46. This process leads to dications from which the pyrroles can be formed by cyclization and elimination of an amine [Eq. (44)]. 

Reactions of enamines with monoimines of o-quinones afford polycylic compounds 228 with an oxazine ring (86MI2).Trifluoroacetylation of enamines with trifluoroacetic acid takes place in the /3-position of the enamine. Ketones (229) thus formed in an acidic medium afford fused 1,3-oxazines (230) (82JOC3339). Treatment of amines with silyl isothiocyanate gives not only pyrimidine derivatives but also l,3-oxazine-4-thiones (231) (81CCC2696). 

Keywords 1,3-cyclohexanedione, anilines, melt-reaction, solid-solid reaction, enamine ketone... 

Akopova synthesized enamine ketone derivative 107 of dibenzo[18]crown-6 (Scheme 55) which exhibits columnar mesomorphism [8]. An interesting feature of compound 107 is the hydrogen-bond mediated stabilization within the side group. 

Rieche et al.bl report (without giving experimental details) that the enamine ketone (53) is converted by hydrogen peroxide into the cyclic peroxide (54). The principle of this reaction is the same as that of the reaction of mesityl oxide with hydrogen peroxide. 

Bromination of enamine ketone 792 leads to the formation of 793 (Scheme 197). The Br in 793 can be replaced with hydrazine to give 2-(l-hydrazino-l,2-oxopropylidene)imidazoline 794. Cyclization between the nitrogen termini in 810 with aldehyde or acid chlorides affords 795, imidazo[2,T [l,2,4]triazine 796 and imidazo[2,Tr/ [l,2,4]triaze-pines 797 and 798, respectively <1997SC2433>. 

The anodic dimerization of enamine ketones or esters in MeCN-NaC104 at a graphite anode is followed by an elimination of 1 mol of amine, which results in the formation of pyrroles [31]. 

Enamination. Ketone condensation with secondary amines using BSA [or bis(trimethylsilyl)urea] as dehydrating agent is quite advantageous. lodomethane is also present. 

Hydrogen Bonding Ring Containing Polymers Poly(enamine—Ketones)... 

Monomeric and polymeric enamine-ketones were synthesized by the condensation reaction of 1,3-diketones with amines. These compounds exhibit liquid crystalline properties when heated to appropriate temperatures. The transition temperatures of these compounds are much lower than those of the aromatic hydrocarbon analogs. 

High solubilities in organic solvents of these compounds together with the low transition temperatures suggest possible processability for the poly(enamine-ketones) as high strength materials. 

The proton nmr of a monomeric enamine-ketone prepared from benzoylacetone and m-xylylenediamine,1, shows a internal hydrogen bonding signal at 11.5-13.5. Its nmr signals are listed in Table I. The nmr signals are in agreement with an enamine-ketone structure. 

Melting Behavior of Some Oliglomeric Polyphenyls and Enamine-Ketones... 

Several polymers with various combinations of enamine-ketone and phenyl rings as the rigid case connected with alkylene and m-xylylene groups were prepared by condensation reaction of diamines with bis-(0-diketones). High yields of poly(enamine-ketones) I-VIII with moderate molecular weight were obtained,... 

We are now studying both the lyotropic and thermotropic liquid crystalline properties of poly(enamine-ketones). Also in progress is the synthesis of poly(enamine-ketones) derived from diaminoarenes, polymers containing all ring systems. We hope to obtain rod-like polymers with both lyotropic and thermotropic liquid crystalline properties that permit their processing into useful end products. 

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