Tuning the Basicity of Synergic Bimetallic Reagents: Switching the Regioselectivity of the Direct Dimetalation of Toluene from 2,5- to 3,5 Positions

摘要

Organolithium reagents have long enjoyed iconic status amongst synthetic chemists, in part because of their unrivaled ability to affect directed metalation (lithiation, lithium-hydrogen exchange) reactions on arenes; heteroarenes, and related compounds. If the objective is to generate non-lithium metal-carbon bonds with subordinate metals having lower reactivity than lithium, then usually these bonds must be made indirectly by first forming a lithium-carbon bond and subsequently carrying out a metathesis reaction with a subordinate metal salt Recently, however, there is increasing realization that direct (subordinate) metalation with low-polarity metals magnesium, zinc, aluminum, or manga-nese(II) is now achievable with imaginatively composed bases.