MgI2-Mediated Solvent-Controlled Divergent Ring-Opening Cyclization/Addition of Spirocyclopropyl Indanediones
Ting Yang1, Ze-Gang Ma2, Wen-Hui Zhang1
1College of Pharmacy, Guizhou University of Traditional Chinese Medicine, Guiyang 550025, P. R. China.
None:
MgI2-mediated formal (3 + 2) cycloaddition (ring-opening cyclization) and ring-opening iodination-Michael addition of spirocyclopropyl indanediones and nitroalkenes have been developed respectively in tetrahydrofuran and toluene, which constitutes an efficient protocol for the solvent-controlled divergent synthesis of spirocyclopentyl indandiones (up to 95% yield, >20:1 dr) and 2,2-disubstituted indanediones (up to 68% yield). Based on control experiments and a high-resolution mass spectrometry experiment, a plausible reaction mechanism has been proposed.
Related Concept Videos
[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction
Cycloaddition Reactions: Overview
Diels–Alder Reaction Forming Bridged Bicyclic Products: Stereochemistry
Cycloaddition Reactions: MO Requirements for Thermal Activation
Diels–Alder Reaction Forming Cyclic Products: Stereochemistry
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.

![Solid-phase Synthesis of [4.4] Spirocyclic Oximes](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F58508.jpg&w=3840&q=50)
