Benzocyclobutanone Synthesis Exploiting Acylsilanes as Photofunctional Directing Groups

A novel mode of reactivity for siloxycarbenes was discovered involving the light induced intramolecular carboannulation of acylsilanes bearing tethered vinyl ketones. To exploit this unique reactivity, we herein describe the discovery that acylsilanes can be employed as photofunctional directing groups in chemical synthesis. First, a protocol for the acylsilane directed ruthenium catalysed C-H olefination of benzoylsilanes using vinyl ketones was developed (where the use of TFE proved critical for accelerating C-H functionalisation). Subsequent photochemical irradiation of the olefin-tethered benzoylsilanes promoted carboannulation via transient siloxycarbene intermediates to afford unique benzocyclobutanone derivatives primed for further synthetic elaboration.