Acylsilanes in rhodium(III)-catalyzed directed aromatic C-H alkenylations and siloxycarbene reactions with C-C double bonds

Acylsilanes are known to undergo a 1,2-silicon-to-oxygen migration under thermal or photochemical conditions to form siloxycarbenes. However, there are few reports regarding the application of siloxycarbenes in organic synthesis and surprisingly, their reaction with C-C double or triple bonds remains virtually unexplored. To facilitate such a study, previously inaccessible aromatic acylsilanes containing an ortho-tethered C-C double bond were identified as suitable substrates. To access these key intermediates, we developed a new synthetic method utilizing a rhodium-catalyzed oxidative Heck-type olefination involving the application of an acylsilane moiety as a directing group. When exposed to visible-light irradiation, the ortho-olefinated acylsilanes underwent a smooth intramolecular cyclization process to afford valuable indanone derivatives in quantitative yields. This result paves the way for the development of new transformations involving siloxycarbene intermediates. Circle of light: A rhodium(III)-catalyzed olefination process allows access to ortho-olefinated aroylsilanes through C-H functionalization in high yields. A light-induced cyclization leads to silyl ethers of indanones in excellent yields as determined by NMR spectroscopy. Mechanistically, the latter transformation proceeds via siloxycarbene intermediates.