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Cyclocondensation between fatty acid hydrazides and 1,1,1-trifluoro-4-alkoxy-3-alken-2-ones: Introducing a trifluoromethylated head onto fatty acid moieties

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posted on 2017-08-11, 13:50 authored by Wystan K. O. Teixeira, Helena A. Gonçalves, Débora L. de Mello, Sidnei Moura, Darlene C. Flores, Alex F. C. Flores

This paper reports the regioselective synthesis of new trifluoromethylated lipid derivatives, namely, 1-(5-hydroxy-5-trifluoromethyl-3-alkyl-4,5-dihydro-1H-pyrazol-1-yl)alkan-1-ones, through cyclocondensation reactions between a series of fatty hydrazides (palmitoyl, stearoyl, and oleoyl hydrazides) obtained from fatty acids from renewable resources (1,1,1-trifluoro-4-alkoxy-3-alken-2-ones [F3CC(O)CH˭C(R1)OR, where R1 = H and R˭Et; R1 = –(CH2)6CH3, –(CH2)6CH3, –(CH2)8CH3, –(CH2)9CH3, –(CH2)10CH3, –(CH2)12CH3, –(CH2)2Ph], and R˭Me). Experimental observations showed that the lipophilic characteristic of 5-hydroxy-5-trifluoromethyl-4,5-dihydro-1H-pyrazoles (5–7) prevent the acid catalyzed dehydration to aromatization of 1H-pyrazole ring, although in some cyclocondensations a proportion of the aromatic derivative 1-(5-trifluoromethyl-3-alkyl-1H-pyrazol-1-yl)alkan-1-one was obtained. All products were characterized using multinuclear (1H, 13C, 19F) NMR spectroscopy.

Funding

This work was supported by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior [Grant Number PROAP/PPGQTA/FURG].

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