The enantioselective synthesis of axially chiral biaryls by a copper-catalyzed Diels−Alder/retro-Diels−Alder reaction of 2-pyrones with alkynes is reported herein. Using electron-deficient 2-pyrones and electron-rich 1-naphthyl acetylenes as the reaction partners, a broad range of axially chiral biaryl esters are obtained in excellent yields (up to 97% yield) and enantioselectivities (up to >99% ee). DFT calculations reveal the reaction mechanism and provide insights into the origins of the stereoselectivities. The practicality and robustness of this reaction are showcased by gram-scale synthesis. The synthetic utilizations are demonstrated by the amenable transformations of the products.
We report herein an asymmetric inverse-electron-demand Diels–Alder (IEDDA) reaction of electron-deficient 2-pyrones with various phenyl vinyl selenides catalyzed by a chiral bis(oxazoline)/Cu(OTf)2 complex. Using a side arm-modified chiral bis(oxazoline)ligand, a variety of [2,2,2]-bicyclic lactones with phenyl selenide substituents were obtained with good to excellent yields (up to 99% yield) and enantioselectivities (up to 98% ee) under mild conditions. Based on this strategy, enantioselective synthesis of Corey lactone was accomplished in a highly concise manner.
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