Sergio Brondani

Synthesis of 1,1,1-trihalo-4-methoxy-4-[2-heteroaryl]-3-buten-2-ones, the corresponding butan-1,3-dione and azole derivatives

The synthesis of 1,1,1-trihalo-4-methoxy-4-[2-thienyl]-3-buten-2-ones, 1,1,1-trihalo-4-methoxy-4-[2-furyl]-3-buten-2-ones and the respective trihalomethyl 1,3-butanone derivatives by trihaloacylation of dimethoxy acetals derived from 2-acetylthiophene and 2-acetylfuran are reported. This is a convenient method to obtain fluorinated and chlorinated 1,3-dielectrophiles from 2-acetylthiophene and 2-acetylfuran. The fluorinated 1,3-dielectrophiles were used to synthesize five new 2-thienyl- and 2-furylazoles. The structure of all products were assigned by 1HH- and 13C NMR and mass spectrometry.

Synthesis of hydroxypyrazoles and 1-methyl-3-isoxazolones via haloform reactions

Abstract The synthesis of a new series of hydroxypyrazoles ( 2a – f ) and 2-methyl-3-isoxazolones ( 3a – d ) from the cyclocondensation reaction of trichloromethyl-substituted 1,3-dielectrophiles ( 1a – f ) with dry hydrazine and N -methylhydroxylamine is reported. The regiospecific cyclocondensation took place with the elimination of the trichloromethyl group in a haloform type reaction when acetonitrile under basic medium was used. The structure of compounds 2 and 3 were determined mainly by 1 H and 13 C NMR spectroscopy.

5-Trifluoromethyl-1,2-dimethyl-1H-pyrazolium chlorides: synthesis and 1H, 13C, 19F and 35Cl NMR chemical shifts

Abstract The one-pot synthesis of nine novel 5-trifluoromethyl-1,2-dimethyl-1H-pyrazolium chlorides 2 from the cyclocondensation of 4-alkoxy-1,1,1-trifluoro-3-alken-2-ones 1 [CF3C(O)CH=C(R1)OR, where R1=H, Me, n-Pr, n-Hex, Ph, 4-Me-C6H4, 4-F-C6H4, 4-Cl-C6H4, 4-NO2-C6H4, and R=Me, Et] with 1-2-dimethyl hydrazine, in quantitative yields, is reported. The 1 H , 13 C , 19 F and 35 Cl NMR chemical shifts of compounds 2 also are described.

Microwave-assisted synthesis of novel 5-trichloromethyl-4,5-dihydro-1H-1-pyrazole methyl esters under solvent free conditions

Twelve novel 5-trichloromethyl-4,5-dihydro-1H-1-pyrazole ethyl esters have been synthesized in good yields (70-98%) by using environmentally benign microwave induced techniques. The compounds were synthesized from the cyclocondensation of 1,1,1-trichloro-4-alkoxy-3-alken-2-ones [CCl3C(O)C(R2)=C(R1 )OR, where R, R2 = H, alkyl; R1 = H, alkyl and aryl] with hydrazine methyl carboxylate. The advantages obtained by the using of microwave irradiation under solvent-free conditions, rather than a conventional method, were demonstrated.

One‐Pot Synthesis of Pyrazole‐5(3)‐carboxyamides

Abstract A convenient one‐pot synthesis of eight pyrazole‐5(3)‐carboxyamides from the reaction of the 5(3)‐trichloromethylpyrazoles with amines, in good yield, is reported. These reactions show that the trichloromethyl group is a convenient precursor to carboxyamide groups.

Synthesis of 6-(2-furyl) and 6-(2-thienyl)-4-trifluoromethylpyrimidinones and pyrimidines from 4-(2-heteroaryl)-4-methoxy-1,1,1-trifluoro-3-buten-2-ones

Neste trabalho e apresentada a sintese, em rendimentos razoaveis (50-67%), de novos sistemas biheterociclicos, duas 6-(2-heteroaril)-4-trifluormetil-2-(1H)-pirimidinonas (2a,b) e uma serie de dez 6-(2-heteroaril)-4-trifluormetilpirimidinas (3a,b - 7a,b) a partir da ciclocondensacao de 1,1,1-trifluor-4-(2-heteroaril)-4-metoxi-3-buten-2-onas com ureia e amidinas. As estruturas de todos os compostos foram atribuidas pelos dados de analise elementar, espectrometria de massas e dados de RMN 1 H e 13 C. Os dados de RMN 1 H e 13 C sao mostrados de maneira sistematica. Tambem apresentamos os dados de difracao de raios-X de um monocristal da 2-amino-6-(tien-2-il)-4-trifluormetilpirimidina (5b). The synthesis of biheterocyclic systems 6-(2-furyl)-pyrimidines and 6-(2-thienyl)pyrimidines in reasonable yields (50-67%), two 6-(2-heteroaryl)-4-trifluoromethyl-2-(1H)pyrimidinones (2a,b) and a series of ten 6-(2-heteroaryl)-4-trifluoromethylpyrimidines (3a,b 7a,b) from the cyclocondensation of 1,1,1-trifluoro-4-(2-heteroaryl)-4-methoxy-3-buten-2-ones with urea and amidines is reported. Structures of all compounds have been elucidated by elemental analysis, mass spectrometry and 1 H, 13 C NMR measurements. The 1 H and 13 C NMR data are systematically reported. The X-ray diffraction data for monocrystal from 2-amino-4trifluoromethyl-6-(thien-2-yl)-pyrimidine (5b) are reported.

The effect of pressurized carbon dioxide on the cyclocondensation reaction between 4-alkoxy-1,1,1-trifluoro-3-alken-2-ones and hydrazines

The synthesis of 1-unsubstituted and 1-phenyl-5-trifluoromethylpyrazoles from the reaction of 4alkoxy-1,1,1-trifluoro-3-alken-2-ones [CF3C(O)CH=C(R )OR, where R = Me, Et and R = H, Me, Ph] with hydrazines [NH2NHR , where R = H, Ph] in pressurized carbon dioxide is reported for the first time. Reaction conditions such as pressure, temperature and time were evaluated. The methodology developed herein was suitable to synthesize products in moderate to excellent yields (60 % 96 %) and short reaction times (15 45 min).

Haloacetylated enol ethers: 18

A convenient method for the synthesis of eight alkyl 6-[4,5-dihydroisoxazol-3-yl(-pyrazol-3(5)-yl)]hexanoates from the cyclocondensation of methyl 10,10,10-trifluoro[chloro]-9-oxo-7-methoxydec-7-enoates and hydroxylamine hydrochloride or hydrazine hydrochloride, respectively, in ethanol as solvent is reported. The reaction of methyl 10,10,10-trichloro-9-oxo-7-methoxydec-7-enoates with hydrazines furnished the pyrazole derivatives with the simultaneous transformation of trichloromethyl to carboxyl group.