The static and dynamic structures of the amide derivatives of racemic and (R)-(+)-2-methoxy-2-phenyl-3,3,3-trifluoropropanoic acid (MPTA) with diisopropyl amine (1), meso-2,6-dimethylpiperidine (2), (R)-(−)- and (S)-(+)-2-methylpiperidine (3 and 4, respectively) were investigated by proton nmr spectroscopy. The piperidine rings adopt a single dominant conformation in which the substituent methyl groups occupy axial positions. One of the isopropyl groups of 1 is oriented in the same way as the corresponding side of the piperidine ring of 2–4 but the other (syn to carbonyl oxygen) is turned so that the methyl groups are toward the carbonyl oxygen and the oxygen lies in the plane bisecting the C—C—C angle. Rotation about the amide C(O)—N bond of 1 is accompanied by concurrent rotation about each of the N—iPr single bonds. The free energies of activation of the hindered rotation about the C(O)—N bond in 1–4, 81 kJ/mol, 77 kJ/mol, 77 kJ/mol, and 79 kJ/mol, respectively, are higher than found in most other hindered amides, suggesting that buttressing due to the steric crowding around the amide functionality is felt throughout the rotational pathway.

Darzens type condensation of chloromethyl p-tolyl sulfone with benzaldehyde, acetaldehyde, acetone, benzophenone, and cyclohexanone, with potassium tert-butoxide as base, gave good to excellent yields of the corresponding α,β-epoxy sulfones (1). The condensation of α-chloroethyl p-tolyl sulfone and bromomethyl p-tolyl sulfone with benzaldehyde also gave excellent yields. With the aldehydes only the trans-epoxides were formed, which is shown by nuclear magnetic resonance spectroscopy. The mechanism and stereochemistry are discussed.

Optically pure (S)-cyclopent-2-en-1-ol, [Formula: see text] (c 1.1, CHCl3), and (S)-3-methoxycyclopentene, [Formula: see text] (c 3.86, n-hexane), were prepared from ethyl (1R,2S)-2-hydroxycyclopentanecarboxylate, which is readily available by yeast reduction of ethyl 2-oxocyclopentanecarboxylate. The optical purity of the alcohol was determined from its Mosher ester, and that of the ether by gas chromatography using a Ni-4-Pin column. Keywords: (S)-cyclopent-2-en-1-ol, (S)-3-methoxycyclopentene.

The three fluorine atoms of N,N-dialkyl amide and chloride derivatives of 2-methoxy-2-phenyl-3,3,3-trifluoropropanoic acid are magnetically nonequivalent below –60 °C and exhibit a clear ABC coupling pattern from which chemical shifts and geminal coupling constants are readily derived. The chemical shifts span a range of about 10 ppm and the geminal coupling constants average about 110 Hz. A five bond coupling of about 5 Hz is observed between the hydrogens of the methoxy group and one of the nonequivalent fluorine atoms of the trifluoromethyl group. Barriers to the hindered rotation about the single bond to the trifluoromethyl group are in the range 36–46 kJ/mol.

Chem. 65, 2461 (1987).Boron oxide has been found to act as an efficient reagent in the preparation of a number of formate esters by the direct esterification of formic acid with the alcohol. The reaction is most appropriate for primary and secondary alcohols, including unsaturated alcohols. The formate ester so produced is free of contamination by unreacted alcohol.

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