P-Enaminoketones

Regioselective synthesis of substituted 3-cyano-2(lT/)-pyridinethiones and -selenones from unsymmetrical p-enaminoketones 90MI5. 

VpF and /ff couplings have been determined by Przyborowski et al from an analysis of the low-temperature spectrum of T-isopropyloamino-T-phenyl-l-methylene-3,3,4,4-tetrafluorocyclopentan-2,5-dione, a member of a newly synthesised series of fluorinated P-enaminoketones. Two-bond F-F... 

TABLE 11 Thermal Behavior of the Lanthanide Complexes P-Enaminoketone L13H of the A/-Alkyl... 

Enantiotropic mesophase, 4—5 P-enaminoketonate complexes lanthanide crmiplexes, 64-65, 66t structure, 64/... 

Schiff s base ligands, alkyl chains of, 71f smectogenic lanthanide, 72/ P-enaminoketonate complexes lanthanide complexes, 64-65, 66f... 

The Hantzsch pyrrole synthesis is a reaction used to synthesize pyrroles from a p-enaminoketone or ester generated by the reaction between ammonia or an ammonia surrogate with a p-diketone or p-ketoester and an a-haloketone. The initial three coniponent reaction reported by Hantzsch involved the reaction between ethyl acetoacetate 8 and chloroacetone 9 in the presence of aqueous ammonia to give the corresponding pyrrole 10 in approximately 50% yield. ... 

Rapid method to prepare 3,4-disubstituted 2-trifluoromethylqumolines 94 by a palladium catalyzed tandem Sonogashira-alkyne carbocyclization of p-trifluoro-methyl p-enaminoketones 93 with arynes has been suggested (Scheme 38) [59]. 

Intramolecular coupling also takes place in the anodic oxidation of N-benzyl- and N-P-phenethyl-enaminoketones. The oxidation was carried out in 0.3 M NaC104/ CH3OH at 10 °C using an undivided cell and graphite electrodes 15). 

The pyridine 2-thione 302 is readily produced by the reaction of the enaminoketone 300 (from acetylacetone and morpholine) with the thioamide 301 (Ar = p-FC6H4) in ethanol at room temperature (equation 124)151. 

A soln. of the startg. isoxazole in methanol or ethanol hydrogenated with Raney-Ni at ca. 50 p.s.i.g. until 1 equivalent of Hg has been absorbed enaminoketone (Y 88%) refluxed 0.5 hr. in toluene with sulfur as oxidant, PgSg and sand with efficient stirring > 3-(2,6-didilorophenyl)-5-methylisothiazole (Y 51%). - By this method isothiazoles previously difficult to obtain can be readily prepared. F. e., also with diloranil as oxidant, s. D. N. McGregor et al.. Tetrahedron 25, 389 (1969). 

An interesting approach to the canthin-4-one alkaloid family has recently been reported by Tremmer and Bracher and involves a 1,3-dipolar cycloaddition of the readily available 1-ethynyl-p-carboline 301 with various nitrile oxides (Scheme 54) (2015T4640). The initially formed isoxazoles 302 were then cleaved reductively, and this was followed by heating the resulting enaminoketones 303 in DMF at 150 °C to give 6-substituted canthin-4-ones 304 in high yields. 

Cal D, Zagorski P (2011) Synthesis of phosphorylated enaminoketones and their application in the preparation of trifluoromethyl-functionatized 2-phosphonopyrroles. Phosphorus Sulfur Silicon 186 2295-2302... 

In contrast, when the reaction was carried out at 150 °C, the enaminoketone 265 cyclized to form the benzoxathianesulfonyl chloride 267 (Equation 84). Benzoylacetone (268) reacts with excess chlorosulfonic acid (10 equivalents) at room temperature (three hours), followed by treatment with dimethylamine to give the bisdimethylamide (269, 33%) (Scheme 5). In this sequence, direct sulfonation occurs on the methylene carbon atom of the enolic form and subsequent reaction is via the chlorohydrin intermediate and involves expulsion of ketene as has previously been observed in the chlorosulfonation of benzylide-neacetone (see p 82). In the reaction, sulfonation of the phenyl ring occurs in the position meta to the electron-withdrawing carbonyl moiety as would be anticipated. 

In contrast, when the reaction was performed at RT, chlorosulfonation of the aryl enaminoketones (10 R = R = H) occurred at the 4-position para to the hydroxyl group), but cyclization to the benzodioxathiin ring was not observed (see Chapter 4, p 88). 

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