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α‑Lithiobenzyloxy as a Directed Metalation Group in ortho-Lithiation Reactions

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journal contribution
posted on 2020-08-03, 14:39 authored by Carlos Sedano, Rocío Velasco, Claudia Feberero, Samuel Suárez-Pantiga, Roberto Sanz
The α-lithiobenzyloxy group, easily generated from aryl benzyl ethers by selective α-lithiation with t-BuLi at low temperature, behaves as a directed metalation group (DMG) providing a direct access to o-lithiophenyl α-lithiobenzyl ethers. This ortho-directing effect is reinforced in substrates bearing an additional methoxy group at the meta position. The generated dianions can be reacted with a selection of electrophiles including carboxylic esters and dihalosilanes or germanes, which afford interesting benzofuran, sila­(germa)­dihydrobenzofuran, and silachroman derivatives from simple aryl benzyl ethers.

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