Lithium‐Bromide Exchange versus Nucleophilic Addition of Schiff’s base: unprecedented tandem cyclisation pathways

Samantha Orr, Emily Chantelle Border, Philip C. Andrews, Victoria Blair

Research output: Contribution to journalArticleResearchpeer-review

Abstract

By exploring lithium‐bromide exchange reactivity of aromatic Schiff’s bases with tert‐butyllithium (tBuLi) we have revealed unprecedented competitive intermolecular and intramolecular cascade annulation pathways leading to valuable compounds such as iso‐indolinones and N‐substituted anthracene derivatives. A series of reaction parameters were probed including solvent, stoichiometry, sterics and organolithium reagent choice in order to understand the influences limiting such ring closing pathways. In the case of having two viable reactivity options for the organolithium on the imine; namely nucleophilic addition or lithium‐bromide exchange, a surprising competitive nature was observed where nucleophilic addition dominated, even under cryogenic conditions. Considering the most commonly used solvents for lithium‐bromide exchange, tetrahydrofuran (THF) and diethyl ether (Et2O), contrasting reactivity outcomes were revealed with nucleophilic addition promoted in THF, while Et2O yielded almost double the conversion of cyclic products than in THF.
Original languageEnglish
Pages (from-to)11876-11882
Number of pages7
JournalChemistry - A European Journal
Volume25
Issue number51
DOIs
Publication statusPublished - 2019

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