Adriano Rosa

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.

HALOACETYLATED ENOL ETHERS: 16[5] REGIOSPECIFIC SYNTHESIS OF 5-TRICHLOROMETHYL-PYRAZOLES

ABSTRACT The regiospecific synthesis and isolation of three series of 5-trichloromethyl-pyrazoles 2f–j, 3a–j and 4a–j from the cyclocondensation of 1,1,1-trichloro-4-alkoxy-3-alken-2-ones (1a–f) or trichloroacetyl containing β-diketones (1g–j) with dry hydrazine and phenyl-hydrazine is reported. It was established by 1H- and 13C-NMR spectroscopy that the 5-hydroxy-5-trichloromethyl-4,5-dihydro-1H-pyrazole intermediates 2a–j were formed quantitatively.

HALOACETYLATED ENOL ETHERS. XVII.1* A CONVENIENT SYNTHESIS OF 5-TRICHLOROMETHYL-1,2-DIMETHYL- 1H-PYRAZOLIUM CHLORIDES

ABSTRACT The one-pot synthesis of nine 5-trichloromethyl-1,2-dimethyl-1H-pyrazolium chlorides 2 from the cyclocondensation of 4-alkoxy-1,1,1-trichloro-3-alken-2-ones [CCl3C(O)C(R2)= C(R1)OR, where R1 = H, Me, Et, n-Pr, (CH2)5CO2Et, CH2Br, Ph, 4-Br-C6H4; R2 = H, Me; and R = Me, Et] with 1,2-dimethylhydrazine is reported. For Part 16, see Ref. [12].

SYNTHESIS OF 3-METHYLISOXAZOLE- 5-CARBOXAMIDES AND 5-[(1H-PYRAZOL-1-YL)CARBONYL]- 3-METHYLISOXAZOLES

ABSTRACT The one-pot synthesis of six 3-methylisoxazole-5-carboxamides 2 [where the N-substituents are R1 = H, Me and R2 = Ph, CH2Ph, n-Bu, C(CH3)2Et, 3-methylisoxazol-5-yl] and twelve 5-[(1H-pyrazol-1-yl)carbonyl]-3-methyl isoxazoles 3 and 4 [where the pyrazole substituents are R3 (C5/C3) = CO2Et, CF3 and R5 (C3/C5) = H, Me, Et, Ph] from the 3-methyl isoxazole-5-carboxylic acid, thionyl chloride and the corresponding amine or pyrazole is reported. In the synthesis of 5-[(1H-pyrazol-1-yl)carbonyl]-3-methylisoxazoles we obtained a mixture of 1,3- and 1,5-isomers 3 and 4 in variable ratios, i.e., the substituent R3 (CO2Et and CF3) are present in position 3 or 5 on the pyrazole ring.

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.