𝔖 Bobbio Scriptorium
✦   LIBER   ✦

Assignment of stereochemistry to cyclohexenylidenecyanoacetates by 1H NMR spectroscopy

✍ Scribed by Vassilios Bardakos; Constantine Sandris

Publisher
John Wiley and Sons
Year
1981
Tongue
English
Weight
382 KB
Volume
15
Category
Article
ISSN
0749-1581

No coin nor oath required. For personal study only.

✦ Synopsis

Abstract

The stereochemistry of various pairs of isomeric 2‐cyclohexen‐1‐ylidenecyanoacetates was assigned using ^1^H NMR spectroscopy. The isomers with the γ‐methylene or the γ‐vinyl protons cis to the carbalkoxy group were found to have the signals of these protons at approximately 0.3 ppm and 1 ppm, respectively, downfield relative to their geometrical isomers or the corresponding 2‐cyclohexen‐1‐ylidenemalononitriles. The observation regarding the γ‐vinyl proton proved useful for the assignment of configuration to cyclohex‐enylidenecyanoacetates derived form cholest‐4‐en‐3‐one. The large and constant downfield shift (c. 1 ppm) of the γ‐vinyl proton when cis to the ester group results from the rigid cyclohexenylidenecyanoacetate system, in which the vinylic proton can approach more closely to the magnetically anisotropic ester carbonyl group.

📜 SIMILAR VOLUMES

Structural assignment of monothiocarbono
Structural assignment of monothiocarbonohydrazones by 1H NMR spectroscopy
✍ G. Rajendran; Sampat R. Jain 📂 Article 📅 1984 🏛 John Wiley and Sons 🌐 English ⚖ 416 KB

Analysis of the 'H NMR spectra of several monothiocsrbonohydraones, some of them synthesized for the first time, shows that they exist as two structural isomers. Whereas, in general, the derivatives of aromatic aldehydes conform to a linear structure, the aliphatic carbonyl derivatives conform to he

Structural assignment of isomeric chain
Structural assignment of isomeric chain demethylated retinals by 1H NMR spectroscopy
✍ A. D. Broek; J. M. L. Courtin; J. R. Mellema; J. Lugtenburg; K. Nicolay; K. Dijk 📂 Article 📅 1982 🏛 John Wiley and Sons 🌐 English ⚖ 234 KB

## Abstract Geometric isomers of all‐__trans__‐9‐demethyl‐, −13‐demethyl‐ and −9,13‐bisdemethylretinal were prepared. The 360 MHz ^1^H NMR spectra of 13 geometric isomers of these three demethylated retinal systems have been measured. The chemical shift and coupling constant values in each case all

1H NMR long-range coupling in the assign
1H NMR long-range coupling in the assignment of stereochemistry to 4-imidazolidinones
✍ T. Połoński 📂 Article 📅 1984 🏛 John Wiley and Sons 🌐 English ⚖ 323 KB

Long-range couplings were observed between protons attached to c-2 and c-5 of the 4-imidazolidinone ring. Smce 45(25) has a measurable value only for a trans arrangement of H-2 and H-5, this coupling can be utilized as an easy method of identification of 4-imidazolidinone stereoisomers.

Assignment of the stereochemistry of spi
Assignment of the stereochemistry of spiroxamine by two-dimensional NMR spectroscopy and stereoselective chemical synthesis
✍ W. A. Etzel; W. Gau; W. Krämer; U. Stelzer; J. Weissmüller 📂 Article 📅 1998 🏛 John Wiley and Sons 🌐 English ⚖ 278 KB 👁 2 views

Spiroxamine is a new powdery mildew fungicide in cereals consisting of four biologically active isomers (two diastereomers, four enantiomers). The four isomers were separated by preparative high-performance liquid chromatography (HPLC) on a chiral stationary phase. At this stage it was not possible