Investigation of the Origins of Regiochemical Control in [4+2] Cycloadditions of 2-Pyrones and Alkynylboronates

[摘要]：The [4+2] cycloaddition of 2-pyrones with substituted alkynylboronates has been studied. In general, the highest yielding cycloadditions were obtained in reactions that employed a trimethylsilyl-substituted alkynylboronate. The highest regioselectivities were obtained using the corresponding phenyl-substituted alkyne, which provided a single regioisomer irrespective of the 2-pyrone used. Mechanistic studies suggest that the high regioselectivity observed is due to stabilization of a zwitterionic transition state.

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