Nilo E. K. Zimmermann

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].

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.

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.

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.

MOLECULAR STRUCTURE OF HETEROCYCLES: 17O NMR CHEMICAL SHIFTS: TORSION ANGLE RELATIONSHIPS IN 3-ALKYL SUBSTITUTED 4,5-DIHYDROISOXAZOLES AND ISOXAZOLES†

A quantitative relationship between the 17O substituent chemical shifts (SCS) of γ-alkyl substituents and the torsion angles calculated by the AM1 method is reported. A series of 3-alkyl substituted 5-trichloromethyl-5-hydroxy-4,5-dihydroisoxazoles and 5-trichloromethyl isoxazoles [where 3-alkyl substituents are Me, Et, n-Pr, iso-Bu, BrCH2, iso-Pr, Br2CH and tert-Bu] as model compounds were used. †For Parts 1–6, see References 14-15a, 15b-16, [19a], [19b].

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.