Giovani P. Bastos

Regiospecific acylation of acetals. A convenient method to obtain β-methoxyvinyl trichloromethyl ketones

Abstract The regiochemistry of the acylation of enol ethers, generated in situ, from acetals of unsymmetrical ketones is reported. These results demonstrate a convenient one-pot method to obtain a series of β-methoxyvinyl trichloromethyl ketones [CCl 3 COCHC(OMe)R, where R=Et, n -Bu, i -Pr, (CH 2 ) 2 C(OMe)CHC(O)CCl 3 and (CH 2 ) 5 CO 2 CH 3 )] in high yields.

A convenient one-pot synthesis of 5-carboxyisoxazoles: trichloromethyl group as a carboxyl group precursor

Abstract The one-pot synthesis of ten 5-carboxyisoxazoles from the cyclocondensation of β-alkoxyvinyl trichloromethyl ketones [CCl 3 C(O)C(R 2 )C(R 1 )OR, where R 1 , R 2 =H, Me and R=Me, Et] and 2-trichloroacetyl cyclohexanone with hydroxylamine is reported. This work shows that the trichloromethyl group attached to β-alkoxyvinyl trichloromethyl ketones (a heterocyclic CCC building block) is an excellent carboxyl group precursor.

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.

Molecular Structure of Heterocycles: 6. Solvent Effects on the 17O Nmr Chemical Shifts of 5-Trichloromethylisoxazoles

A multilinear-regression analysis using the Kamlet-Abboud-Taft (KAT) solvatochromic parameters in order to elucidate and quantify the solvent effects on the 17O chemical shifts of three 5-trichloromethylisoxazoles [(1a) non-, (1b) 3-methyl- and (1c) 4-methyl-substituted] is reported. The chemical shifts of ring oxygen atom, O1, of compounds 1a-c show dependencies (in ppm) on the solvent polarity-polarizability of -4.8p*, -3.2p*, -8.9p*, on the solvent hydrogen-bond-donor (HBD) acidities 0.9a, -0.2a, -2.7a and the solvent hydrogen-bond-acceptor (HBA) basicities -0.4b, 1.9b, 0.9b, respectively. The data of net charges of O1 and dipole moment, obtained from MO calculations (AM1), are compared with the solvent effect parameters obtained for compounds 1a-c.

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.