Divergent ring-opening coupling between cyclopropanols and alkynes under cobalt catalysis

Area of Science:

• Organometallic Chemistry
• Catalysis
• Organic Synthesis

Background:

• Cyclopropanols are strained cyclic alcohols with unique reactivity.
• Unactivated internal alkynes are challenging coupling partners in organic synthesis.
• Developing selective catalytic methods for functionalizing these substrates is of significant interest.

Purpose of the Study:

• To develop a novel catalytic system for the ring-opening coupling of cyclopropanols and unactivated internal alkynes.
• To achieve control over chemoselectivity, yielding either beta-alkenyl ketones or multisubstituted cyclopentenol derivatives.
• To elucidate the reaction mechanism and identify key intermediates and controlling factors.

Main Methods:

• Utilized cobalt-diphosphine catalysts for the coupling reactions.
• Investigated the effect of various reaction conditions, with a focus on solvent choice.
• Employed Density Functional Theory (DFT) calculations to support proposed reaction pathways.

Main Results:

• Achieved efficient ring-opening coupling reactions between cyclopropanols and internal alkynes.
• Demonstrated good to excellent yields and regioselectivities for both product types.
• Identified solvent as a critical factor in controlling chemoselectivity between beta-alkenylation and [3+2] annulation.

Conclusions:

• Cobalt-diphosphine catalysts provide a versatile platform for cyclopropanol functionalization.
• The reaction proceeds via a cobalt homoenolate intermediate, with selectivity dictated by reaction conditions.
• The proposed mechanism involving ring-opening, alkyne insertion, and subsequent transformations is supported by computational studies.