Sequential oxonium–olefin–alkyne cyclization for the stereoselective synthesis of (octahydro-1H-pyrano[3,4-c]pyridin-5-yl)methanone derivatives

A broad range of aldehydes undergo a smooth cascade cyclization with (E)-5-(3-phenylprop-2-ynylamino)pent-3-en-1-ol in the presence of BF3·OEt2 at room temperature to furnish a novel series of (octahydro-1H-pyrano[3,4-c]pyridin-5-yl)methanone derivatives in good yields and diastereoselectivities. This cascade process provides a simple and proficient alternative for the stereoselective construction of fused pyranopiperidine derivatives.