Visible-Light-Induced Radical-Cascade Brominative/Spirocyclization of Biaryl Ynones and CBr4: Synthesis of Spiro[5.5]trienones without External Additives

Abstract A visible-light-induced brominative spirocyclization of biaryl ynones with CBr4 for the synthesis of spiro[5.5]trienones is reported here. This protocol also features broad functional group tolerance and operational simplicity and achieves moderate to excellent yields as well as sustainable photocatalyst- and additive-free reaction conditions at room temperature under air. This strategy thus provides a green and practical synthetic avenue to access spiro[5.5]trienone scaffolds, and the resulting products exhibit diverse synthetic versatility for subsequent structural modifications.