Synthesis of trifluoromethylated dihydrofurans by addition of
1,3-dicarbonyl compounds to alkenes promoted by manganese(III) acetate
Emre Biçer*a and Mehmet Yılmazb
TUBITAK Marmara Research Center, Energy Institute,41470 Gebze, Kocaeli, Turkey
Department of Chemistry, Faculty of Arts and Sciences, Kocaeli University, 41380 Umuttepe, Kocaeli, Turkey
E-mail: bicer_emre@yahoo.com
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Abstract
Radical addition reaction of trifluoromethyl-1,3-dicarbonyl compounds (1a-e) with various alkenes (2a-f) was investigated in the presence of manganese(III) acetate. As a result of these reactions trifluoromethyl ketone substituted dihydrofuran and bicyclic enol ether derivatives were obtained. A formation of dihydrofuran’s mechanism was proposed for all compounds. Radical addition reactions with 1,1-disubstituted alkenes were obtained in good yields, however with cyclic alkenes were shown poor yields.
Keywords: Manganese(III) acetate, dihydrofuran, oxidative addition, trifluoromethyl compounds
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Introduction
The use of organofluorine compounds has been attracted significant attention due to the unique influence of a fluorine substituent on the chemical, physical and physiological properties of these compounds. Thus, organofluorine chemistry impacts many areas of everyday life and technology.1 These compounds show a large number of industrial uses in lubricants, fire extinguisher agents, surfactants, pharmaceuticals and agrochemicals.2 Since the fluorine atom is highly reactive and difficult to control, the synthesis of organic fluorine compounds is an ongoing area of research in synthetic organic chemistry.3
Traditional methods for the synthesis of organofluorine compounds are direct fluorination 4 and fluoroalkylation.5 Manganese(III) mediated oxidative radical addition has become a valuable method for the formation of C-C bonds in the last three decades. Since manganese(III) acetate is effective for the formation of C-C bonds within the intramolecular addition to form lactones,6 dihydrofurans,7 furans,8 and lactams.9 Another way of obtaining organofluorine compounds is
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