Stereocontrolled Construction of 1‑Vinylindanes via Intramolecular Cyclization of <i>o</i>‑Cinnamyl Chalcones

In this paper, a concise route for the synthesis of 1-vinylindanes is described, including (i) NaBH4-mediated reduction of o-cinnamyl chalcones and (ii) sequential BF3·OEt2-mediated intramolecular annulation of the resulting alkenols. The plausible mechanism is proposed and discussed herein. This protocol provides highly effective stereocontrolled cinnamyl-enone cross-coupling to construct three contiguous trans-trans stereocenters and one (E)-configured alkenyl or styryl group.