ortho-Lithiations Reassessed: the Advantages of Deficiency Catalysis in Hydrocarbon Media

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• 作者：D. W. Slocum ; Thomas K. Reinscheld ; Christopher B. White ; Michael D. Timmons ; Philip A. Shelton ; Matthew G. Slocum ; Rebecca D. Sandlin ; Erica G. Holland ; Damir Kusmic ; John A. Jennings ; Kristen C. Tekin ; Quang Nguyen ; Steven J. Bush ; Julia M. Keller ; Paul E. Whitley
• 刊名：Organometallics
• 出版年：2013
• 出版时间：March 25, 2013
• 年：2013
• 卷：32
• 期：6
• 页码：1674-1686
• 全文大小：469K
• 年卷期：v.32,no.6(March 25, 2013)
• ISSN：1520-6041

文摘

Hydrocarbon media based metalation procedures involving 鈥渄eficiency catalysis鈥?are described for the ortho-lithiation of anisole (A), p-chloroanisole (p-ClA), o-, m-, p-methylanisoles (o-, m-, p-MA), the three dimethoxybenzenes (DMB鈥檚), dimethylaniline (DMA), dimethybenzylamine (DMBA), m-methoxydimethylaniline (m-MeODMA), and tetramethyl-p-phenylenediamine (p-TMPDA). These procedures involve certain mechanistic considerations, which must be fine-tuned to maximize the extent of metalation (EoM). Our working hypothesis is that a controlled deoligomerization of the n-BuLi hexamer found in hydrocarbon media will afford a 鈥渟weet spot鈥?of deoligomerization such that a maximally efficient metalation medium can be formed. In many cases, a substoichiometric ratio of equivalent TMEDA to n-BuLi is 0.1鈥?.2:1.0, but certain substrates suffer multiple sites of metalation under these conditions, so different promoted hydrocarbon media systems incorporating measured equivalents of an ether have been formulated. This paper represents the summary of our successful efforts to render ortho-lithiations safer, greener, and more atom-economical by use of hydrocarbon solvent media. EoM鈥檚 of 11 of the 12 substrates under these atom-economical conditions range from 87 to 97%.