Abstract
Metal carbene is an active synthetic intermediate, which has shown versatile applications in synthetic chemistry. Although a variety of catalytic methods have been disclosed for the generation of carbene species from different precursors, there is an increasing demand for the development of efficient and practical approaches for the in-situ formation of metal carbene intermediates with structural diversity and unrevealed reactivity. Herein we report a gold-catalyzed cascade protocol for the assembly of polycarbocyclic frameworks in high yields under mild reaction conditions. Mechanistic studies indicate that the unique β-aryl gold-carbene species, generated via gold-promoted 6-endo-dig diazo-yne cyclization, is the key intermediate in this reaction, followed by a [4 + 2]-cycloaddition with external alkenes. In comparison to the well-documented metal carbene cycloadditions, this carbene intermediate serves as a 4-C synthon in a cycloaddition reaction. A variety of elusive π-conjugated polycyclic hydrocarbons (CPHs) with multiple substituents are readily accessible from the initially generated products by a mild oxidation procedure.
Highlights
Metal carbene is an active synthetic intermediate, which has shown versatile applications in synthetic chemistry
We describe our recent results in this direction, a cycloaddition reaction of the cross-conjugated β-aryl gold-carbene II serving as a 4-C synthon, which generated in situ through a selective 6-endo-dig diazo-yne carbocyclization[44,45,46,47]
Given the fact that the formation of 3′ with these catalysts should go through a carbene/alkyne metathesis process (CAM)[49,50,51,52,53,54,55,56,57,58], the gold-complexes, which have shown unique ability to selectively activate alkyne species with the pendant diazo group served as a latent functionality[41,42,43,59], were evaluated
Summary
Metal carbene is an active synthetic intermediate, which has shown versatile applications in synthetic chemistry. We describe our recent results in this direction, a cycloaddition reaction of the cross-conjugated β-aryl gold-carbene II serving as a 4-C synthon, which generated in situ through a selective 6-endo-dig diazo-yne carbocyclization[44,45,46,47] This reaction features an asynchronous process[48]: the gold-carbene intermediate reacts with an olefin to form the carbocation species III, which could be successfully intercepted by the tethering aryl group rather than the cyclopropanation, leading to a general access for the assembly of polycarbocyclic frameworks in high to excellent yields (Fig. 1c). These products could be readily transformed into π-conjugated polycyclic hydrocarbons (CPHs) under mild oxidation procedure
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
