Fluorine-containing 2,4-dioxo acids in the synthesis of heterocyclic compounds

Synthesis and reactions of halogen-containing chromones

“…18 Data on 2-halochromones are quite scarce and data on 3-polyhaloalkylchromones are totally missing. The introduction of a halogen atom into the 3-position of the chromone system changes crucially the reactivity of the pyrone ring with respect to nucleophiles and stipulates the broad synthetic potential of 2-unsubstituted 3-halochromones.…”

“…Analysis of the published data demonstrates that of the diverse halogen-containing chromones, 3-halo-and 2-polyhaloalkylchromones, as well as chromones with the perfluorinated benzene ring have now been studied most comprehensively. 18 Data on 2-halochromones are quite scarce and data on 3-polyhaloalkylchromones are totally missing. The introduction of a halogen atom into the 3-position of the chromone system changes crucially the reactivity of the pyrone ring with respect to nucleophiles and stipulates the broad synthetic potential of 2-unsubstituted 3-halochromones.…”

“…As regards the ability of the halogen atom to act as a leaving group, 2-and 3-halochromones markedly surpass chromones halogenated at the benzene ring (except for 5,6,7,8-tetrafluorochromones in which the fluorine atom located in the para-position relative to the carbonyl group is susceptible to nucleophilic substitution 18 ). The halogen atom situated in the b-position with respect to the carbonyl group is the most active; therefore, 2-halochromones surpass 3-halochromones and are similar to acid halides in reactivity.…”

“…To complete the picture, the review covers the most important publications of the 1960s ± 1970s not included in the monograph 2 and also the sparse data available on halo-containing thiochromones and furochromones. The methods of synthesis and chemical properties of chromones with the perfluorinated benzene ring have been covered in a number of reviews; 2,18,19 therefore, we do not consider them here. The reactions of heteroanalogues of…”

Synthesis of methyl 3-acyl-6-amino-5-cyano-4-phenyl-4H-pyran-2-carboxylates and their rearrangement into 2-hydroxy-4-[hydroxy(R)methylidene]-3-oxo-5-phenylcyclopent-1-ene-1-carbonitriles

“…Methyl 2,4-dioxobutanoates are used in the synthesis of biologically active compounds [10,11]. However, their reaction with benzylidenemalononitrile was not studied.…”