Synthesis of 2‑Nickela(II)oxetanes from Nickel(0) and Epoxides: Structure, Reactivity, and a New Mechanism of Formation

2-Nickelaoxetanes have been frequently
invoked as reactive intermediates
in catalytic reactions of epoxides using nickel, but have never been
isolated or experimentally observed in these transformations. Herein,
we report the preparation of a series of well-defined nickelaoxetanes
formed via the oxidative addition of nickel(0) with epoxides featuring
ketones. The stereochemistry of the products is retained, which has
not yet been reported for nickelaoxetanes. Theoretical calculations
support a bimetallic ring-opening/closing pathway over a concerted
oxidative addition. Initial reactivity studies of a nickelaoxetane
demonstrated protonolysis, oxidatively induced reductive elimination,
deoxygenation, and elimination reactions when treated with the appropriate
reagents.