Studies on the stereochemical assignment of 3-acylidene 2-oxindoles

Abstract

The designation of E/Z-geometrical isomers in 3-acylidene 2-oxindoles by NMR spectroscopy can lead to erroneous assignment of alkene stereochemistry because of the narrow chemical shift range observed over a large series of analogues. In contrast, UV-Vis spectroscopy offers a convenient and more reliable method for alkene stereochemical assignment. A combination of X-ray crystallography and theoretical studies shows that the observed differences in UV-Vis spectroscopic behaviour relate to the twisted conformation of the Z-isomers that provides reduced conjugation and weaker hypsochromic (blue-shifted) absorbances relative to those of the E-isomers.

Saccharomonosporine A inspiration; synthesis of potent analogues as potential PIM kinase inhibitors

“…In addition, the IR data exhibited absorption bands at 3395 (NH) and 1712, 1662 (2C]O). According to previous reports, 33,34 H-4 (d H 8.31 ppm) and H-8 (d H 7.45 ppm) chemical shis suggest the E conguration at C-3/C-8 double bond. Furthermore, both E and Z conformers' energies were minimized and the distance between H-4, H-10, H-13 and H-14 were determined that were found to be less than 5 A in E form and more in Z form, from this points the presence of 1 H-1 H NOESY correlations (crosspeaks) between H-4 and H-10, H-13 and H-14 together with their absence between H-4 and H-8 (Fig.…”

Highly Efficient Reversible Hydrogenation of Carbon Dioxide to Formates Using a Ruthenium PNP‐Pincer Catalyst

“…It was observed that the arylative Meyer–Schuster rearrangement of heterocycle‐containing tertiary alkynols was equally efficient (Scheme ). For instance, the relevant13 3‐acylidene‐2‐oxindole derivative 7a could be smoothly afforded in reasonable yield and with total Z diastereoselectivity starting from 3‐ethynyl‐3‐hydroxyindolin‐2‐one 6a (Scheme ) 14. Curiously, adducts 7b and 7c , initially obtained as their corresponding hemiacetals by 1,2‐addition reaction of methanol to the α,β‐unsaturated ketone moiety, evolves through protonation, dehydration, and final hydration to oxindole‐tethered tetrasubstituted olefins 8b and 8c .…”

2-Iodoisatogens: Versatile Intermediates for the Synthesis of Nitrogen Heterocycles

“…Notably, this latter class of compounds has been shown to undergo bio-reduction in red blood cells thereby exhibiting potent antiplasmodial activity. 10 Finally, in relation to our recent interest in the synthesis and spectroscopic properties of 3-acylidene 2-oxindoles, 11 our observation that displacement of the iodide could be quite facile (Scheme 4, Eq (3)) suggested that 2-iodoisatogens could in fact offer a facile strategy for the synthesis of the isomeric 2-acylidene 3-oxindoles. These compounds are relatively rare and have been far less studied with respect to their biological activity or cycloaddition chemistry as compared to the 2oxindole isomers.…”