Stereochemistry and dipole moments of ?,?-Unsaturated heterocyclic ketones

One-Pot Synthesis of Polysubstituted Indolizines by an Addition/Cycloaromatization Sequence

“…Compounds 2a , 1-phenylbut-2-en-1-one ( 2c ), 3-(2-chlorophenyl)-1-(4-fluorophenyl)prop-2-en-1-one ( 2e ), and 3-(4-methoxyphenyl)-1-(4-fluorophenyl)prop-2-en-1-one ( 2j ) were obtained from commercial suppliers. All other α,β-unsaturated aldehyde/ketones ( 2b , 2d , 2f – 2i , and 2k ) ,,− and α-aminonitriles − were prepared according to literature procedures.…”

Nitration of Some 3-(2-Furyl)-2-propenones with Dinitrogen Tetraoxide

“…The coupling constant for the olefinic protons in the 1 H NMR spectra is equal to ~16 Hz, indicating trans-configuration of the double bond. The greater intensity of the ν C=C band as compared to ν C=O (ν C=O /ν C=C = 0.3-0.5) in the IR spectra of ketones Ia, Ib, IIa, and IIb suggests that the conjugated carbonyl group and ethylene moiety are arranged s-cis [5]. The intensity ratio of the C=O and C=C absorption bands in the IR spectra of aldehydes Il and IIl is equal to 2.5, which is typical of transoid orientation of the corresponding groups [6].…”

“…According to [5], ketone Ia exists mainly as syntrans-s-cis conformer, while aldehyde Il is characterized by syn-trans-s-trans conformation. We have determined the configuration of compounds Ia, Ib, Il, IIa, IIb, and IIl.…”

“…The coordinate system was set in such a way that the x axis passed through positions 2 and 5 of the furan ring, and the y axis, through position 3. The required parameters of 2-substituted furan ring and dipole moments of particular groups and bonds in molecules Ia, Ib, Il, IIa, IIb, and IIl were taken from [5]. The dipole moment of the nitro group in position 4 of the furan ring was assumed to be 4.01 D (i.e., as in nitrobenzene [7]), and the moment of chlorine in aromatic ring was taken equal to 1.59 D [7].…”

“…orthoand meta-Aromatic protons in IIb-IIe give doublets with coupling constants of 8.0-8. 5 Hz, and aromatic protons in IIa and IIIf appear as multiplets. Signals from the methyl group protons were also present in the spectra of ketones IId, IIe, IIIg, and IIIh.…”