Proton nuclear magnetic resonance spectra of cyclic monoenes: hydrocarbons, ketones, heterocycles, and benzo derivatives

Improvement of the Antifungal Activity Against Botrytis Cinerea of Syringic Acid, a Phenolic Acid From Grape Pomace

“…However, it presented different chemical shifts, due to a different chemical environment produced by the quinone ring. The spectrum of the other precursor molecule (syringic acid) showed only one aromatic signal (δ 7.35 s), but in the synthesized product, this signal disappeared and two new signals appeared (δ 6.158 d (J=2.0 Hz) and 6.423 d (J=2.0 Hz)) this coupling constant suggests a 4-bond coupling 30 . These signals belong to the two protons of the quinone-imine ring.…”

New Dienophiles: 1‐Acetylvinyl Arenecarboxylates. Reactivity toward cyclopentadiene and exocyclic dienes

“…This loss of stereoselectivity with respect to that observed in the cycloadditions of methyl vinyl ketone to the same dienes (1, 2 and cyclopentadiene) confirms the hypothesis that attractive van der W a d s [26] and dipole-dipole interactions [27] between the dienophile substituents and the dienes are responsible for the Alder rule The 'exo' allylic protons H-C (1 p. 4p) are assumed to be more deshielded than the 'endo' hydrogens H-C(la,4a) due to the anisotropy of the 5,12-epoxide. Typical coupling constants between H,C (1,3,4) confirm a half-chair conformation of the cyclohexene systems [29] and allow the distinction between pseudo-axial and pseudo-equatorial H-atoms (cJ: Table 4). Interestingly, a long-range 5J (H, H) coupling constant of ca.…”

Reaction of unsaturated compounds with ethyl benzenesulfenate and trimethylsilyl isothiocyanate

“…In compound 25b, the proton HCSPh is found as a doublet of doublets of doublets and has two large spin spin cou pling constants with the protons HCNCS and H(5´) ( 3 J 4,3 = 6.9 Hz and 3 J 4,5´ = 9.6 Hz), as well as one small spin spin coupling constant with the proton H(5) ( 3 J 4,5 = = 2.9 Hz), which indicates the diequatorial arrangement of the substituents. 25 Therefore, compound 25b is the trans 3 isothiocyanato 4 phenylthiocyclohex 1 ene.…”