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Nitrile oxide cycloadditions in supercritical carbon dioxide.
Connie K Y Lee1, Andrew B Holmes, Bushra Al-Duri
1Melville Laboratory for Polymer Synthesis, Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, UK CB2 1EW. abh1@cam.ac.uk
Chemical Communications (Cambridge, England)
|November 16, 2004
Summary
The regioselectivity of dipolar cycloadditions using mesitonitrile oxide in supercritical carbon dioxide can be controlled by adjusting density. Magnesium bromide mediation enhances stereoselectivity in reactions with pent-1-en-3-ol.
Area of Science:
- Organic Chemistry
- Green Chemistry
- Physical Chemistry
Background:
- Dipolar cycloadditions are crucial reactions in organic synthesis.
- Supercritical carbon dioxide (scCO2) offers a tunable and environmentally friendly reaction medium.
- Controlling regioselectivity and stereoselectivity is key for efficient synthesis.
Purpose of the Study:
- To investigate the regioselectivity of mesitonitrile oxide cycloadditions in scCO2.
- To explore the influence of scCO2 density on reaction outcomes.
- To evaluate the stereoselectivity of magnesium bromide-mediated cycloadditions.
Main Methods:
- Performing dipolar cycloadditions of mesitonitrile oxide with various dipolarophiles in scCO2.
- Systematically varying the density of scCO2 to observe effects on regioselectivity.
- Utilizing magnesium bromide as a mediator for specific cycloadditions.
Main Results:
- Regioselectivity of the cycloadditions was tunable via changes in scCO2 density.
- Magnesium bromide-mediated cycloaddition with pent-1-en-3-ol showed enhanced stereoselectivity compared to conventional solvents.
- scCO2 provides a viable medium for controlling cycloaddition outcomes.
Conclusions:
- Supercritical carbon dioxide is an effective medium for tuning the regioselectivity of dipolar cycloadditions.
- Density modulation in scCO2 offers a novel approach to control reaction pathways.
- Enhanced stereoselectivity achieved through mediation in scCO2 highlights its potential in complex synthesis.