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Metal-free Synthesis of Ynones from Acyl Chlorides and Potassium Alkynyltrifluoroborate Salts
Published on: February 24, 2015
An unexpected equilibrium process associated with a standard approach to ynone synthesis
Mary M Jackson1, Carolyn Leverett, Jennifer F Toczko
1GlaxoSmithKline, Chemical Development, Five Moore Drive, P.O. Box 13398, Research Triangle Park, North Carolina, 27709, USA.
The Journal of Organic Chemistry
|July 6, 2002
Summary
Weinreb amides react completely with alkynyllithium reagents, unlike morpholine amides which show incomplete reactions due to equilibrium. Using excess alkynyllithium with morpholine amides enables useful ynone synthesis.
Area of Science:
- Organic Chemistry
- Synthetic Chemistry
Background:
- Weinreb amides are commonly used in organic synthesis for controlled acylation.
- Morpholine amides are an alternative amide class with different reactivity profiles.
Purpose of the Study:
- To directly compare the reactivity of Weinreb amides and morpholine amides with alkynyllithium reagents.
- To investigate the formation of ynones from these amide classes.
Main Methods:
- Direct reaction of Weinreb amides and morpholine amides with stoichiometric alkynyllithium reagents.
- Reaction of morpholine amides with excess alkynyllithium reagents at 0 degrees C.
Main Results:
- Weinreb amides undergo complete reaction with stoichiometric alkynyllithium reagents to form ynones.
- Morpholine amides exhibit incomplete reactions with stoichiometric alkynyllithium reagents due to an unexpected equilibrium.
- Using excess alkynyllithium reagents with morpholine amides provides a synthetically useful method for ynone synthesis at 0 degrees C.
Conclusions:
- The reactivity difference between Weinreb and morpholine amides stems from an equilibrium process in morpholine amide reactions.
- Excess alkynyllithium is crucial for achieving efficient ynone synthesis with morpholine amides.
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