Intermediate Control: Unlocking Hitherto Unknown Reactivity and Selectivity in N-Conjugated Allenes and Alkynes

Area of Science:

• Organic Chemistry
• Synthetic Methodology
• Catalysis

Background:

• Controlling selectivity in organic synthesis is a persistent challenge.
• Selective C-C π-bond functionalization offers novel synthetic routes.
• N-conjugated allenes and alkynes are promising substrates for developing new reactions.

Purpose of the Study:

• To review recent developments in intermediate-controlled functionalization of activated π-systems.
• To highlight new reactivity, selectivity, and atom-economical strategies.
• To provide mechanistic insights into related transformations.

Main Methods:

• Utilizing allenamide-derived intermediates for cross-coupling and hydrofunctionalization.
• Employing electrophile-promoted reactions like haloalkynylation and hydroamination.
• Investigating ynamide reactivity via activator modulation.
• Exploring metal-free couplings of 1,3-enynes with indole substrates.

Main Results:

• Achieved unprecedented selectivity in Pd-catalyzed allenamide-alkyne cross-coupling via neighboring group chelation.
• Developed electrophile-promoted hydrofunctionalizations including haloalkynylation and hydroamination.
• Demonstrated chemoselective annulation of ynamides and divergent C-H annulation of vinylogous ynamides.
• Showcased N-electron polarization in 1,3-enynes for metal-free couplings.

Conclusions:

• Intermediate-controlled functionalization provides effective methods for selective synthesis.
• New strategies expand the scope of accessible organic molecules.
• Further research in activator design and mechanistic studies is warranted.