N-Oxides as Control Element for the Direction of a Sigmatropic Rearrangement: Application as a Switch for...

Area of Science:

• Organic Chemistry
• Chemical Synthesis

Background:

• Sigmatropic rearrangements are fundamental organic reactions.
• Controlling the stereochemical outcome of rearrangements is crucial for synthesis.
• N-oxides and alkoxylamines are versatile functional groups in organic chemistry.

Purpose of the Study:

• To investigate the influence of solvent on the (2,3)-sigmatropic rearrangement between N-oxides and alkoxylamines.
• To explore the potential of this rearrangement in controlling reaction pathways.
• To introduce and characterize the 'Reverse Meisenheimer Rearrangement'.

Main Methods:

• Systematic variation of solvents (protic vs. aprotic) to study rearrangement direction.
• Analysis of reaction products using spectroscopic techniques.
• Investigation of the effect of temperature and substrate substituents on reaction rates.
• Attachment of N-oxide fragments to fluorescent molecules to demonstrate functional control.

Main Results:

• Protic solvents favor the N-oxide intermediate, while aprotic solvents favor the alkoxylamine.
• Reaction rate is influenced by temperature and alkene substituents.
• N-oxide functionalization enabled on/off switching of fluorescence in attached molecules.
• The conversion of alkoxylamines to N-oxides was achieved and termed the 'Reverse Meisenheimer Rearrangement'.

Conclusions:

• Solvent polarity is a key factor in directing the (2,3)-sigmatropic rearrangement of N-oxides and alkoxylamines.
• This solvent-controlled rearrangement offers a novel strategy for synthetic chemistry.
• The 'Reverse Meisenheimer Rearrangement' expands the synthetic utility of these functional groups.