Synthesis and Reactivity of a Zinc Diazoalkyl Complex: [3+2] Cycloaddition Reaction with Carbon Monoxide.

This work reports the synthesis, characterization, and reactivity of the first example of a well-defined zinc α-diazoalkyl complex. Treatment of zinc(I)-zinc(I) bonded compound L2Zn2 [L = CH3C(2,6-iPr2C6H3N)CHC(CH3)(NCH2CH2PPh2)] or zinc(II) hydride LZnH with trimethylsilyldiazomethane affords zinc diazoalkyl complex LZnC(N2)SiMe3. This complex liberates N2 in the presence of a nickel catalyst to form an α-zincated phosphorus ylide by reacting with the pendant phosphine. It selectively undergoes formal [3+2] cycloaddition with CO2 or CO to form the corresponding product with a five-membered heterocyclic core. Notably, the use of CO in such a [3+2] cycloaddition reaction is unprecedented, reflecting a novel CO reaction mode.