Synthetically Important Alkali-Metal Utility Amides: Lithium, Sodium, and Potassium Hexamethyldisilazides, Diisopropylamides, and Tetramethylpiperidides

Most synthetic chemists will have at some point utilized a sterically demanding secondary amide (R2N−). 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 l...

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Published in:Angewandte Chemie International Edition Vol. 52; no. 44; pp. 11470 - 11487
Main Authors: Mulvey, Robert E., Robertson, Stuart D.
Format: Journal Article
Language:English
Published: Weinheim WILEY-VCH Verlag 25.10.2013
WILEY‐VCH Verlag
Wiley Subscription Services, Inc
Edition:International ed. in English
Subjects:
Acidity
Alkali metals
Amides
Chemists
Congeners
heterometallic compounds
Lithium
molecular structure
Potassium
secondary amide
Sodium
solution state
Solvents
Utilities
molecular structure
heterometallic compounds
secondary amide
solution state
alkali metals
ISSN:1433-7851, 1521-3773, 1521-3773
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Summary:Most synthetic chemists will have at some point utilized a sterically demanding secondary amide (R2N−). 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. Essential utilities: The Li, Na, and K salts of 1,1,1,3,3,3‐hexamethyldisilazide (HMDS, red), diisopropylamide (DA, green), and 2,2,6,6‐tetramethylpiperidide (TMP, blue) constitute one of the most synthetically important classes of compounds. In this Review, these bulky secondary amides are considered collectively, and their effectiveness as reagents discussed on the basis of their solution behavior and solid‐state structures.
Bibliography:EU
istex:65182146227A9D4FA5E0AE320135C70F3E327FDC
Royal Society/Wolfson Foundation
Royal Society of Edinburgh
ArticleID:ANIE201301837
ark:/67375/WNG-B1ZM3LKP-H
Nuffield Foundation
EPSRC
University of Strathclyde
AstraZeneca
ObjectType-Article-1
SourceType-Scholarly Journals-1
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ISSN:1433-7851
1521-3773
1521-3773
DOI:10.1002/anie.201301837