¹H‐NMR‐Spektroskopische Untersuchungen an methylsubstituierten Cyclohexen‐(4)‐dicarbonsäure‐(1,2)‐anhydriden

Abstract

Abstract-Chemical shifts and coupling constants of methyl substituted 4-cyclohexene-I ,2-dicarboxyJic anhydrides were determined. The NMR data demonstrate the boat conformation of the cis-anhydrides. The orientation of the cis-anhydride ring relative to the cyclohexene boat depends on the constitution and configuration of the compounds, and can be deduced from coupling constants and 6-values of the HI-and H,-protons. Methyl groups in the neighbourhood of these protons shift the resonance frequencies dependent upon molecular conformation.Zusammenfassung-Es wurden die chemischen Verschiebungen und Kopplungskonstanten von methylsubstituierten Cyclohexen-(4)-dicarbonsaure-(l,2)-anhydriden bestimmt. Die NMR-Daten beweisen die Bootkonformation der cis-Anhydride. Die Orientierung des cis-Anhydridringes relativ zum Cyclohexenboot wird durch die Konstitution und Konfiguration der Verbindungen bestimmt und kann von den Kopplungskonstanten und den 6-Werten der HI-und H,-Protonen abgeleitet werden. Methylgruppen in Nachbarschaft zu diesen Protonen verschieben die Resonanzfrequenzen in Abhangigkeit von der konformativen Anordnung.

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

“…A detailed discussion of the conformations of 21 methylsubstituted cyclohexene-4,5-dicarboxylic acid anhydrides of type 102 was given. 317 For the trans compounds, only the rigid halfchair with diequatorial CO groups is possible. For the cis compounds, however, the large values found for 3J(H4, H5) of 9.4 to 10 Hz indicated that the respective CH bonds are eclipsed, and a boat geometry (102a) was proposed for the six-membered ring.…”

Crystal Structure of 3,4,5,6‐Tetrahydrophthalic Anhydride at 150 K

“…± Within the context of studies on the conformations of bicyclic anhydrides, the structure of cis-1,2,3,6-tetrahydrophthalic anhydride C 8 H 8 O 3 has been determined by X-ray diffraction [1]; its crystal structure consists of two symmetryindependent molecules per asymmetric unit. Their conformations are folded, both possessing a boat form for the cyclohexene ring, in agreement with experimental NMR solution data [2] [3]. Crystal packing of the two independent molecules in the unit cell has also been investigated [4], establishing non-bonded interactions of the dipoleÀdi-pole type between local electrical dipoles of the carbonyl groups CO ¥¥¥ CO. Concomitantly, several techniques of semi-empirical and ab initio molecular-orbital calculations have been applied for the determination of the molecular geometry of this compound and its isomers, 3,4,5,6-, 1,2,5,7-, and 1,4,5,6-tetrahydrophthalic anhydrides [5].…”

Preparation of (L)(N,N‘-ethylenebis(salicylideneaminato))- (1,3-butadien-2-yl)cobalt(III) Complexes and Their Utilization in Facile and Regioselective Diels−Alder Reactions

“…The solvent was removed under reduced pressure. The anhydride was extracted into hexane and worked up as in the previous example to give cis- 1,2,3,6-tetrahydrophthalic anhydride ( 21 ) (0.026 g, 0.171 mmol, 84%) (identical to an authentic sample (Aldrich) by 1 H NMR comparison). Co II (salen) ( 6 ) (0.062 g, 0.191 mmol, 95%) was obtained by first treating the initially hexane-insoluble material with aqueous NaOH followed by the procedure outlined above.…”