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Synthetically Important Alkali‐Metal Utility Amides: Lithium, Sodium, and Potassium Hexamethyldisilazides, Diisopropylamides, and Tetramethylpiperidides
Author(s) -
Mulvey Robert E.,
Robertson Stuart D.
Publication year - 2013
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201301837
Subject(s) - chemistry , alkali metal , lithium (medication) , tetrahydrofuran , lithium amide , potassium , amide , tetramethylethylenediamine , lithium diisopropylamide , steric effects , sodium , inorganic chemistry , metal , organic chemistry , medicinal chemistry , deprotonation , catalysis , ion , medicine , enantioselective synthesis , solvent , endocrinology
Most synthetic chemists will have at some point utilized a sterically demanding secondary amide (R 2 N − ). The three most important examples, lithium 1,1,1,3,3,3‐hexamethyldisilazide (LiHMDS), lithium diisopropylamide (LiDA), and lithium 2,2,6,6‐tetramethylpiperidide (LiTMP)—the “utility amides”—have long been indispensible particularly for lithiation (Li‐H exchange) reactions. Like organolithium compounds, they exhibit aggregation phenomena and strong Lewis acidity, and thus appear in distinct forms depending on the solvents employed. The structural chemistry of these compounds as well as their sodium and potassium congeners are described in the absence or in the presence of the most synthetically significant donor solvents tetrahydrofuran (THF) and N , N , N’ , N’ ‐tetramethylethylenediamine (TMEDA) or closely related solvents. Examples of hetero‐alkali‐metal amides, an increasingly important composition because of the recent escalation of interest in mixed‐metal synergic effects, are also included.