Related Experiment Video
Updated: Jun 24, 2026

Efficient Construction of Drug-like Bispirocyclic Scaffolds Via Organocatalytic Cycloadditions of α-Imino γ-Lactones and Alkylidene Pyrazolones
Published on: February 7, 2019
Catalytic intramolecular formal [3 + 2] cycloaddition for the synthesis of benzobicyclo[4.3.0] compounds
Xun Han1, Long-Wu Ye, Xiu-Li Sun
1State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Lu, Shanghai 200032, China.
Abstract:
In the presence of 20 mol % of tributylphosphine, tert-butyl carbonate substrate 3a undergoes smoothly an intramolecular formal [3 + 2] cycloaddition reaction at room temperature to give benzobicyclo[4.3.0] compounds in 99% yield with a 19/81 ratio of 2a and 2a'. The mechanism of the isomerization of the product 2a into 2a' has been investigated in detail. On the basis of this mechanism, two strategies, using 20 mol % of triphenylphosphine or 10 mol % of tributylphosphine in the presence of 20 mol % of Ti(O(i)Pr)(4), have been established for the selective construction of benzobicyclo[4.3.0] compounds. Under neutral conditions, the reactions of compounds 3a-g afford benzobicyclo[4.3.0] compounds 2a-g with high selectivities in good to excellent yields. In addition, alpha-methyl alpha,beta-unsaturated ester 3h also works well to give the corresponding product 2h with one quaternary carbon center in 99% yield under neutral and room temperature conditions.
More Related Videos
09:35Preparation of a Corannulene-functionalized Hexahelicene by Copper(I)-catalyzed Alkyne-azide Cycloaddition of Nonplanar Polyaromatic Units
Published on: September 18, 2016
07:50Efficient Synthesis of All-Carbon Quaternary Centers via the Conjugate Addition of Functionalized Monoorganozinc Bromides
Published on: May 26, 2019
Related Concept Videos
Cycloaddition Reactions: Overview
Cycloaddition Reactions: MO Requirements for Thermal Activation
Reduction of Benzene to Cyclohexane: Catalytic Hydrogenation
[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction
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.