We report a Ni-catalyzed regioselective alkylarylation of vinylarenes with alkyl halides and arylzinc reagents to generate 1,1-diarylalkanes. The reaction proceeds well with primary, secondary and tertiary alkyl halides, and electronically diverse arylzinc reagents. Mechanistic investigations by radical probes, competition studies and quantitative kinetics reveal that the current reaction proceeds via a Ni(0)/Ni(I)/Ni(II) catalytic cycle by a rate-limiting direct halogen atom abstraction via single electron transfer to alkyl halides by a Ni(0)-catalyst.

The 1,3-dipolar cycloaddition between azides and alkynes provides new means to probe and control biological processes. A major challenge is to achieve high reaction rates with stable reagents. The optimization of alkynyl reagents has relied on two strategies: increasing strain and tuning electronics. We report on the integration of these strategies. A computational analysis suggested that a CH → N aryl substitution in dibenzocyclooctyne (DIBO) could be beneficial. In transition states, the nitrogen of 2-azabenzo-benzocyclooctyne (ABC) engages in an n→π* interaction with the C=O of α-azidoacetamides and forms a hydrogen bond with the N–H of α-diazoacetamides. These dipole-specific interactions act cooperatively with electronic activation of the strained π-bond to increase reactivity. We found that ABC does indeed react more quickly with α-azidoacetamides and α-diazoacetamides than its constitutional isomer, dibenzoazacyclooctyne (DIBAC). ABC and DIBAC have comparable chemical stability in a biomimetic solution. Both ABC and DIBO are accessible in three steps by the alkylidene carbene-mediated ring expansion of commercial cycloheptanones. Our findings enhance the accessibility and utility of 1,3-dipolar cycloadditions and encourage further innovation.

We report a Ni‐catalyzed regioselective α‐carbonylalkylarylation of vinylarenes with α‐halocarbonyl compounds and arylzinc reagents. The reaction works with primary, secondary, and tertiary α‐halocarbonyl molecules, and electronically varied arylzinc reagents. The reaction generates γ,γ‐diarylcarbonyl derivatives with α‐secondary, tertiary, and quaternary carbon centers. The products can be readily converted to aryltetralones, including a precursor to Zoloft, an antidepressant drug.

Cycloalkynes and their utilization in cycloaddition reactions enable modular strategies spanning the molecular sciences. Strain�imparted by deviation from linearity�enables sufficient alkyne reactivity without the need for a catalyst (e.g., copper); however, the design and synthesis of stable reagents with suitable reactivity remains an ongoing challenge. We report the incorporation of an endocyclic sulfate within a dibenzocyclononyne scaffold to generate a cyclononyne displaying remarkable reactivity and stability. Through computational analyses, we revealed that the endocyclic sulfate group shares nearly half the total strain energy, providing an activation strategy that reduces alkyne bending. Rehybridization of alkyne carbons in the formation of the heterocyclic product relieves strain both at the reactive site and in the transannular sulfate group. This mode of remote activation enables rapid reactivity while minimizing distortion�and strain�at the reactive site (the alkyne). The result: a design strategy for a new class of cycloalkynes with increased stability and reactivity.

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