Heterosubstituted 4-Vinylimidazoles – Preparation and Diels-Alder Reactions

Lovely, Carl J.; Ray, Abhisek; Mukherjee, Sabuj; Das, Jayanta; Bhandari, Manoj K.; Herath, Apsara K.; Yousufuddin, Muhammed

doi:10.3987/com-18-s(f)27

Cited by 1 publication

(1 citation statement)

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“…Presumably, therefore, rearomatization must occur via a proton transfer pathway, although in certain cases a radical pathway has been postulated [45]. Although we have no direct evidence for the mechanism [33,34,46], our assumption is that it most likely occurs through C4 protonation followed by deprotonation of C8b. In this manifold, it is not clear what the proton source is or what the proton acceptor is for the second step.…”

Section: Dft Investigationmentioning

confidence: 77%

Room Temperature Diels–Alder Reactions of 4-Vinylimidazoles

Fulton,

Hartzell,

Dias

et al. 2024

Molecules

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In the course of studying Diels–Alder reactions of 4-vinylimidazoles with N-phenylmaleimide, it was discovered that they engage in cycloaddition at room temperature to give high yields of the initial cycloadduct as a single stereoisomer. In certain cases, the product precipitated out of the reaction mixture and could be isolated by simple filtration, thereby avoiding issues with aromatization observed during chromatographic purification. Given these results, intramolecular variants using doubly activated dienophiles were also investigated at room temperature. Amides underwent cycloaddition at room temperature in modest yields, but the initial adducts were not isolable with Nimid-benzyl-protected systems. Attempts to extend these results to the corresponding esters and hydroxamate were less successful with these substrates only undergoing cycloaddition at elevated temperatures in lower yields. Density functional theory calculations were performed to evaluate the putative transition states for both the inter- and intramolecular variants to rationalize experimental observations.

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