Axially chiral molecules are among the most valuable substrates in organic synthesis. They are typically used as chiral ligands or catalysts in asymmetric reactions. Recent progress for the construction of these chiral molecules is mainly focused on the transition-metal-catalyzed transformations. Here, we report the enantioselective NHC-catalyzed (NHC: N-heterocyclic carbenes) atroposelective annulation of cyclic 1,3-diones with ynals. In the presence of NHC precatalyst, base, Lewis acid and oxidant, a catalytic C–C bond formation occurs, providing axially chiral α-pyrone−aryls in moderate to good yields and with high enantioselectivities. Control experiments indicated that alkynyl acyl azoliums, acting as active intermediates, are employed to atroposelectively assemble chiral biaryls and such a methodology may be creatively applied to other useful NHC-catalyzed asymmetric transformations.
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: Generous financial supports for this work were provided by: the National Natural Science Foundation of China (21672121), the “Thousand Plan” Youth program of China, the Tsinghua University, the Bayer Investigator fellow, the fellowship of Tsinghua-Peking centre for life sciences (CLS), and the China Postdoctoral Science Foundation (2015M570072) to J.W., and KAUST to K.-W.H.