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.