Generation of 3-borylbenzynes, their regioselective Diels-Alder reactions, and theoretical analysis

3-Borylbenzynes were generated in situ from 6-boryl-2-iodophenyl trifluoromethanesulfonates using i-PrMgCl·LiCl and applied to Diels-Alder reactions with substituted furans and pyrroles. The reactions allowed good functional group compatibility and produced the cycloadducts in high yields with high distal selectivities. Effective conversion of the boryl group of the products was achieved. A series of these reactions provides a new method for producing multifunctionalized benzo-fused aromatic compounds. Additionally, the regioselectivities of these Diels-Alder reactions were theoretically analyzed by DFT calculations to find that the reactions were mainly controlled by the electrostatic effect and aryne distortion caused by the boryl group.

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