Photocatalyzed Dual Strain Release of [1.1.1]Propellane with Diazo Compounds

In
recent years, many methods for the synthesis of bicyclo[1.1.1]pentane
(BCP) scaffolds have been successfully established owing to their
remarkable potent bioactive properties. These BCP scaffolds are typically
derived from the single strain release of [1.1.1]propellane. However,
approaches for dual strain release of [1.1.1]propellane remain elusive,
despite the potential to create innovative opportunities for useful
propellane derivatization. In this report, we present herein an efficient
method for photocatalyzed dual strain release of [1.1.1]propellane
with diazo compounds. Many diazo compounds, including those derived
from natural products, such as (+)-borneol, estrone, vitamin E, L-menthol,
metronidazole, and geraniol, can be applied to these transformations.
Importantly, this method allows the cleavage and formation of multiple
C–C bonds in a photocatalyzed tandem intersystem crossing (ISC)/radical
ring-opening/radical–radical recombination process, and the
products can be easily transformed into synthetically challenging
spiro compounds, such as spiro [2.3] and spiro [3.4] compounds.