Configuration of functional trifluoromethylated dienoates, aryldienoates and trienoates

Abstract

The configuration of certain trifluoromethylated functional dienoates, aryldienoates and trienoates is presented by the measurement of their 13 C NMR and 19 F NMR chemical shifts, and their 3 J(C-F), 4 J(H-F) and through-space 5 J(H-F) coupling constants.

Novel Synthesis, Reactivity, and Stereochemistry of Substituted 3-Trifluoromethyl- and 3-Perfluoroalkyl-3-phenoxyprop-2-enal

“…The stereochemistry of 5 was unaffected when the solvent was changed from benzene to chloroform or acetonitrile. Our results are in accord with reported works for similar systems. , …”

“…To establish the Z / E configurations of the double bond of 3a − s , we compared the 5 J HF coupling constant (0.5−1.5 Hz for the E isomer and 0 Hz for the Z isomer) between the aldehydic proton and the vinylic CF 2 or CF 3 group and the 3 J CF coupling constant between the carbon 2 and the fluorine atom of the perfluoroalkyl group. , These couplings were not observed in all cases and are therefore not general.…”

“…Introduction of a trifluoromethyl or perfluoroalkyl group may be accompanied by changes in spatial and electronic structure and may consequently affect the spectral parameters. ,, Often during the synthesis of trifluoromethyl- or perfluoroalkyl-containing vinyl compounds, both configurational isomers Z and E are produced simultaneously. In the case of olefinic compounds bearing a vinylic trifluoromethyl group, determination of the Z or E configuration is based on the comparison between the coupling constant of fluorine atoms and a vicinal vinylic proton ( 4 J HF ( Z ) > 4 J HF ( E )) or the coupling observed between fluorine atoms and the olefinic carbon ( 3 J CF ( Z ) > 3 J CF ( E )). − …”

Indirect Nonbonded Nuclear Spin–Spin Coupling: A Guide for the Recognition and Understanding of “Through-Space” NMR J Constants in Small Organic, Organometallic, and Coordination Compounds

“…The study of through-space J FH SSCCs is closely associated with controversial discussions , concerning the elusive conception of hydrogen bonding. , For instance, it has been debated whether or not some F/H interactions from (C– F / H –O) coupling are due to the existence of F···O–H hydrogen bonds or alternatively due to overlap of electronic clouds from fluorine and an O–H bond (this question is pertinent also for C– F / H –C couplings) . Regardless of the mechanisms involved, the use of J FH values for ascertaining the proximity in space of (F,H) nucleiand thus the specific conformation in solution of the molecules involvedhas been experimentally proven for a range of structures (Scheme ).These include cyclophanes ( 31a , 9h J FH ≈ 6 Hz), o -fluorophenyldiphenylmethanol ( 31b , 5h J FH = 9.2 Hz), 8-fluoro-4-methyl-1-naphthol ( 31c , 5h J FH = 28.4 Hz), trifluoromethylated dienoates, aryldienoates, and trienoates ( 31d – f 5TS J FH ≈ 2 Hz), and fluoromethyl-uracil derivatives ( 31g , 7TS J FH ≈ 2 Hz) . In such compounds, the solvent dependency may be fairly strong with higher J FH values found in the less polar solvents (chlorocarbons, dielectric constant 2 < ε < 9) and correspondingly much weaker values in the more highly polar solvent (DMSO, ε ≈ 47).…”

Highly Regio- and Stereoselective Hydrogermylation of Fluorinated Alkyl Propiolate

“…The Eand Z-configurations of the two regioisomers 2 and 2 were assigned based on the values of the coupling constant [ 3 J(C(2)-F)]; for which 3 J[C(2)-F] of the (Z)-isomer is higher than that of the (E)-isomer ( Figure 2). 16,20 Figure 2 Eand Z-configuration assignments of the two regioisomers  and  To investigate the scope and limitations of the AlCl 3catalyzed hydrogermylation reaction, we next tested the hydrogermylation reaction of alkyne 1a using a less hindered organogermane compound such as Bu 3 GeH. Remarkably, complete -regioselectivity of the hydrogermylation of alkyne 1a was observed.…”