Research Information System
ChemistrySelect, vol.11, no.12, 2026 (SCI-Expanded, Scopus)
Trans- and cis-dihydrofurans were obtained from the radical addition-cyclization of 3-phenyl-oxopropanenitrile (4a) and 1,3-dicarbonyls (4b-d) to various unsymmetrical alkenes (5a-f) mediated by manganese(III) acetate. In the reaction of unsaturated esters with 3-phenyl-oxopropanenitrile (4a) and 1,3-dicarbonyl compounds (4b-c), trans-dihydrofurans were obtained in higher yield than cis-dihydrofurans. Similarly, cis- and trans-dihydrofurans were obtained from the reaction of 1-(2-thienyl)propene (5e) with dimedone (4c), 1-(thiophen-2-yl)butane-1,3-dione (4d), 4,4-difluoro-1-(thiophen-2-yl)butane-1,3-dione (4e), and 4,4,4-trifluoro-1-(thiophen-2-yl)butane-1,3-dione (4f). In addition, different cyclization products were obtained from the reaction of dimedone (4c) with (E)-3-styrylthiophene (5f) as mixtures of trans and cis-dihydrofuran. These compounds were differentiated by 1H NMR, 13C NMR, HMBC, and HSQC techniques. Coupling constants of dihydrofurans that were obtained from the cyclization of 4a-c with alkenes (5a-e), were determined as J = 9.6–11.2 Hz for cis (7a-h) and J = 5.6–7.2 Hz for trans diastereomers (6a-h). However, when C-3 carbon bears difluoroacetyl and trifluoroacetyl groups, it was observed that vicinal couplings of cis-diastereomers remained the same (Jcis = 7.6 Hz for both) while vicinal couplings of trans-diastereomers decreased significantly (Jtrans = 2.8 Hz for 6j and Jtrans = 2.0 Hz for 6k).