Related Experiment Video
Updated: Sep 5, 2025
Facile Preparation of 2Z,4E-Dienamides by the Olefination of Electron-deficient Alkenes with Allyl Acetate
Published on: June 21, 2017
Decarboxylative Cyclization of Proline with o-Alkynylbenzaldehyde through an Unexploited 8π-Electrocyclization: A DFT
Hormoz Khosravi1, Saber Mirzaei2, Saeed Balalaie1
1Peptide Chemistry Research Center, K. N. Toosi University of Technology, P.O. Box 15875-4416, Tehran 1541849611, Iran.
Abstract:
We employed density functional theory (DFT) methods to investigate the most plausible mechanism of cyclization/ring expansion of proline with o-alkynylbenzaldehyde. This one-pot reaction starts with the in situ formation of azomethine ylide, which can undergo three different reaction pathways to form the final product. Two mechanisms are based on nucleophilic addition and 4π-electrocyclization of the azomethine ylide, and our results indicate that the rate-determining step (RDS) of these two cyclizations are 40.1 and 40.2 kcal/mol, respectively. The third novel pathway relies upon 8π-electrocyclization as the key step of this reaction; interestingly, the RDS of this cyclization is ∼20.6 kcal/mol, which shows this route to be most feasible. Thus, we introduce a novel mechanism for the electrocyclization reaction of conjugated azomethine ylides that can help chemists to design and access a new series of compounds.
More Related Videos
Related Concept Videos
01:10α-Alkylation of Ketones via Enolate Ions
03:00Preparation of Epoxides
Epoxides result from alkene oxidation, which can be achieved by a) air, b) peroxy acids, c) hypochlorous acids, and d) halohydrin cyclization.
Epoxidation with Peroxy Acids
Epoxidation of alkenes via oxidation with peroxy acids involves the conversion of a carbon–carbon double bond to an epoxide using the oxidizing agent meta-chloroperoxybenzoic acid, commonly known as MCPBA. Since the O–O bond of peroxy acids is very weak, the addition of electrophilic oxygen of...
01:17Electrophilic Aromatic Substitution: Friedel–Crafts Alkylation of Benzene
01:11Electrophilic Aromatic Substitution: Friedel–Crafts Acylation of Benzene
01:17Thermal Electrocyclic Reactions: Stereochemistry
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
01:01Ketones with Nonenolizable Aromatic Aldehydes: Claisen–Schmidt Condensation
As the self-condensation of ketones is generally not favored in basic conditions, the self-condensed products do not form in the reaction between ketones and benzaldehyde. The general reaction of Claisen–Schmidt...