Regiospecific synthesis of polyfluorinated heterocycles

A series of 10 heterocycles was obtained from the reaction of 1,1,1-trifluoro-4,4-diethoxy-3-buten-2-one and 1,1,1,2,2-pentafluoro-4,4-diethoxy-3-penten-2-one with different dinucleofiles (hydrazine, methyl hydrazine, hydroxylamine and sodium cyanide). The pyrazoles, 4,5-dihydroisoxazoles and pyrrolidinones polyfluoroalkyl substituted were obtained in moderate to good yields under mild conditions.     

Efficient microwave-assisted synthesis of 1-aryl-4-dimethylamino methyleno-pyrrolidine-2,3,5-triones

A microwave-assisted synthesis of a series of 1-aryl-4-dimethylaminomethylene pyrrolidine-2,3,5-triones from the cyclocondensation reaction of ethyl 5,5,5-trichloro-3-dimethylamino methylene-2,4-dioxopentanoate with aniline, 3- or 4-substituted anilines [where the substituents = 3-Me, 3-OMe, 3-OH, 4-Me, 4-F, 4-Cl, 4-Br, 4-NO₂, and 4-COMe] is reported. This process is an efficient alternative to the conventional thermal heating and furnishes the products in a short reaction time (ca. 13 min), under mild conditions and in moderate to good yields (50–76%).     

Resourceful synthesis of pyrazolo[1,5-a]pyrimidines under ultrasound irradiation

Pyrazolo[1,5-a]pyrimidines were synthesized via the ultrasonic sonochemical method using the cyclocondensation reaction of 4-alkoxy-1,1,1-trifluoro-3-alken-2-ones [CF₃C(O)CH = C(R)(OMe) – where R = Me, Bu, i-Bu, Ph, 4-Me–C₆H₄, 4-F–C₆H₄, 4-Cl–C₆H₄, 4-Br–C₆H₄, naphth-2-yl and biphen-4-yl] – with 3-amino-5-methyl-1H-pyrazole in the presence of EtOH for 5 min. This methodology has several advantages, for example, it is a simple procedure, it has an easy work-up, mild conditions, short reaction times (5 min) and produces satisfactory yields (61–98%).     

13C NMR Chemical Shifts of Heterocycles: Empirical Substituent Effects in 5-Halomethylisoxazoles

Evaluation by empirically derived equations for the Substituent effect (α, β, γ, δ) on the ¹³C NMR chemical shifts for C-3, C-4. C-5 and halomethyl-substituent carbon (C-6) in isoxazoles 1-5 [where C-3 substituent (R¹) = H, alkyl or phenyl, C-4 Substituent (R²) = H, alkyl, and C-5 substituent (R³) = di-or trihalomethyl, methyl and H], taking as reference the compound la, is reported. From the calculated values for the α, β, γ, δ effects for each substituent it was possible to estimate the chemical shift of each carbon of the compounds 1–5. The ¹³ C chemical shifts of the C-3, C-4, C-5, C-6 of these compounds, can be estimated with good precision: 94% of the calculated chemical shifts are found to be within ±1.0ppm, and 100% are found to be within ±1.5ppm.     

Invariant linear operators and Fourier analysis

After an elementary introduction to integral representation of functions, the close relationship existent between Fourier analysis and physical systems characterized by invariant linear operators is analysed.     

Reactions of β-methoxyvinyl trifluoromethyl ketones with 2-pyridinecarboxamidrazone: A convenient route to trifluoromethylated 4,5-dihydro-1H-1-picolinoylpyrazole hydrochlorides

A new series of six 3-aryl-5-hydroxy-5-trifluoromethyl-4,5-dihydro-1H-1-picolinoylpyrazole hydrochlorides were synthesised in one-step in high yields by the reaction of β-methoxyvinyl trifluoromethyl ketones with 2-pyridinecarboxamidrazone in the presence of hydrochloric acid. The hydrochloride salts were easily converted to the respective new series of free trifluoromethylated 4,5-dihydro-1H-1-picolinoylpyrazoles using triethylamine in anhydrous diethyl ether. X-ray structure and NMR data from the pyrazole hydrochlorides are reported.     

Convergent procedure for the synthesis of trifluoromethyl-containing N-(pyridinyl-triazolyl)pyrimidin-2-amines

This study describes a simple and efficient procedure to synthesize a novel series of fourteen 4-substituted N-(5-pyridinyl-1H-1,2,4-triazol-3-yl)-6-(trifluoromethyl)pyrimidin-2-amines, where the 4-substituents are H, CH₃, C₆H₅, 4-FC₆H₄, 4-CH₃C₆H₄, 4-CH₃OC₆H₄ and 2-Furyl; from the cyclocondensation reaction of N-[5-(pyridinyl)-1H-1,2,4-triazol-3-yl]guanidines with 4-alkoxy-4-alkyl(aryl/heteroaryl)-1,1,1-trifluoroalk-3-en-2-ones. The reactions were carried out in ethanol under reflux for 18 h and led to 40-68% yields. N-(Pyridyl-triazolyl)guanidine precursors were further obtained from reactions of cyanoguanidine with nicotinic or isonicotinic acid hydrazides and the halogenated enones from trifluoroacetylation of enolethers or acetals.     

Organoallylaluminum reagents promote easy access to trihalomethyl triazolyl homoallylic alcohols analogous to rufinamide

The results of allylation reactions employing allylaluminum reagents are described for 5-substituted (2,6-difluorobenzyl)-4-trifluoro(chloro)acetyl-1H-1,2,3-triazoles (1), in which the 5-substituents are H, Me, and Ph. The allylating reagents were generated in situ by the catalytic insertion of aluminum into allyl and crotyl bromides (2), in order to furnish a new series of twelve trihalomethyl triazolyl homoallylic alcohols (3) at yields of up to 94%. The excellent reactivity of these organoallyl reagents is highlighted as an economical alternative to the indium-mediated reactions to produce homoallylic alcohols, which are important building blocks in organic synthesis.     

Ultrasound promoted synthesis of 5-hydroxy-5-trihalomethyl-4,5-dihydroisoxazoles and beta-enamino trihalomethyl ketones in water

A convenient method for the preparation of 5-hydroxy-5-trihalo-4,5-dihydroisoxazoles and beta-enamino trihalomethyl ketones, from the reaction of 1,1,1-trihalo-4-alkoxy-3-alken-2-ones with hydroxylamine and anilines, respectively, using water as solvent and under ultrasound irradiation is reported.