An alkynylboronate cycloaddition strategy to functionalised benzyne derivatives
作者:James D. Kirkham、Patrick M. Delaney、George J. Ellames、Eleanor C. Row、Joseph P. A. Harrity
DOI:10.1039/c0cc01345e
日期:——
A new approach to benzyne precursors has been developed that involves the [4+2] cycloaddition of trimethylsilyl alkynylboronates with 2-pyrones, followed by oxidation and trifluoromethylsulfonylation of the boronate moiety.
Abstract 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
An Experimental and Computational Investigation of the Diels−Alder Cycloadditions of Halogen-Substituted 2(<i>H</i>)-Pyran-2-ones
作者:Kamyar Afarinkia、Michael J. Bearpark、Alexis Ndibwami
DOI:10.1021/jo048213k
日期:2005.2.1
Diels−Alder reactions of 3- and 5-halo-subsituted 2(H)-pyran-2-ones with both electron-rich and electron-deficient dienophiles afford stable and readily isolable bridged bicyclic lactone cycloadducts. These cycloadditions proceed with excellent regioselectivity and very good stereoselectivity. In contrast, Diels−Alder reactions of 4-halo-subsituted 2(H)-pyran-2-ones afford cycloadducts which are very