Related Experiment Video
Updated: May 27, 2025

Accessing Valuable Ligand Supports for Transition Metals: A Modified, Intermediate Scale Preparation of 1,2,3,4,5-Pentamethylcyclopentadiene
Published on: March 20, 2017
The Mechanism of the Cycloaddition of Substituted Ketenes to Cyclopentadiene Based on the Bent Bond/Antiperiplanar
Mathis Lefebvre1, Paul A Johnson1, Pierre Deslongchamps1
1Département de Chimie, Université Laval, Québec, Quebec G1 V 0A6, Canada.
Abstract:
The [2 + 2] cycloaddition of substituted ketenes with cyclopentadiene producing bicyclo[3.2.0]hept-2-en-6-ones is rationalized by the Bent Bond/Antiperiplanar Hypothesis (BBAH) orbital model. With monosubstituted ketenes, the endo isomer is formed preferentially. The endo and exo isomers are both produced with the cyclobutanone ring in the co-folded in conformation. Computational results support the analysis of the BBAH based mechanism in agreement with experimental results.
More Related Videos
09:35Preparation of a Corannulene-functionalized Hexahelicene by CopperI-catalyzed Alkyne-azide Cycloaddition of Nonplanar Polyaromatic Units
Published on: September 18, 2016
10:17Efficient Construction of Drug-like Bispirocyclic Scaffolds Via Organocatalytic Cycloadditions of α-Imino γ-Lactones and Alkylidene Pyrazolones
Published on: February 7, 2019
Related Concept Videos
Cycloaddition Reactions: MO Requirements for Thermal Activation
[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction
Cycloaddition Reactions: Overview
Cycloaddition Reactions: MO Requirements for Photochemical Activation
Thermal 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.
Conformations of Cycloalkanes