Continuous Flow Generation of Acylketene Intermediates via Nitrogen Extrusion

Area of Science:

• Organic Chemistry
• Chemical Engineering
• Process Chemistry

Background:

• Acylketenes are versatile synthetic intermediates, but their generation and use often require specialized conditions.
• Traditional batch methods for acylketene generation can be challenging to scale and control.
• Flow chemistry offers potential advantages for handling reactive intermediates and improving process control.

Purpose of the Study:

• To develop a continuous flow process for the generation and in-situ utilization of acylketene precursors.
• To optimize reaction parameters, specifically concentration and pressure, for a stable flow protocol.
• To demonstrate the gram-scale synthesis of intercepted acylketene scaffolds.

Main Methods:

• Nitrogen extrusion from suitable precursors to generate reactive acylketene intermediates in a flow reactor.
• Balancing reactant concentration and reactor pressure to ensure process stability and safety.
• Utilizing thermal gravimetric analysis (TGA) to determine optimal reactor coil temperatures for various precursors.
• In-situ reaction of generated acylketenes with volatile amine nucleophiles.

Main Results:

• A robust flow chemistry process for acylketene precursor generation via nitrogen extrusion was established.
• The process successfully balanced concentration and pressure for continuous operation.
• Gram-scale quantities of intercepted acylketene scaffolds were synthesized using volatile amine nucleophiles.
• Simultaneous generation and reaction of two distinct reactive intermediates derived from nitrogen extrusion were achieved.

Conclusions:

• The developed flow chemistry protocol provides a scalable and efficient method for accessing acylketene scaffolds.
• This approach overcomes limitations of traditional batch syntheses for these reactive intermediates.
• The study highlights the utility of flow chemistry for controlled generation and reaction of transient species.