Propynyllithium

Propynyllithium is an organolithium compound with the chemical formula LiC
2CH
3. It is a white solid that is soluble in 1,2-dimethoxyethane, and tetrahydrofuran. To preclude its degradation by oxygen and water, propynyllithium and its solutions are handled under inert gas (argon or nitrogen).[1] Although commonly depicted as a monomer, propynyllithium adopts a more complicated cluster structure as seen for many other organolithium compounds.

Propynyllithium
Names
IUPAC name
1-Lithium-1-propyne
Other names
1-Propyn-1-yllithium
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.022.604
EC Number
  • 224-862-4
  • InChI=1S/C3H3.Li/c1-3-2;/h1H3;/q-1;+1
    Key: ATKCLEUSJFRRKA-UHFFFAOYSA-N
  • [Li+].CC#[C-]
Properties
C3H3Li
Molar mass 46.00 g·mol−1
Appearance Whitish powder
Decomposition
Hazards
GHS labelling:
GHS02: Flammable GHS05: Corrosive
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Synthesis

Various preparations of propynyllithium are known, but the most expeditious route starts with 1-bromopropene:[2][3]

CH3CH=CHBr + 2 BuLi → CH3C≡CLi + 2 BuH + LiBr

Historic routes

It can be prepared by passing propyne gas through a solution of n-butyllithium[4] or by direct metallization of propyne with lithium in liquid ammonia or other solvent. Propyne, however, is an expensive gas, and, therefore, it is sometimes replaced by less expensive gas mixtures used for welding and containing a small percentage of propyne.

Applications

Propynyllithium is used in the organic synthesis as a reactant.[2][4] It is a nucleophile that adds to aldehydes to give secondary alcohols, with ketones to give tertiary alcohols, and with acid chlorides to give ketones containing the propynyl group. These reactions are used in the synthesis of complex natural and synthetic substances such as the drug mifepristone.[5]

References
  1. Greeves, Nicholas (15 April 2001). "Propynyllithium". Encyclopedia of Reagents for Organic Synthesis. onlinelibrary.wiley.com. doi:10.1002/047084289X.rp277. ISBN 978-0471936237.
  2. Samuel G. Bartko; James Deng; Rick L. Danheiser (2016). "Synthesis of 1-Iodopropyne". Org. Synth. 93: 245. doi:10.15227/orgsyn.093.0245.
  3. Toussaint, Dominique; Suffert, Jean (1999). "Generation of 1-Propynyllithium From (Z/E)-1-Bromo-1-propene: 6-Phenylhex-2-yn-5-en-4-ol". J. Org. Chem. 60: 3550–3553.
  4. US 3185553, "Acetylenic lead compounds and gasoline compositions thereof"
  5. Hazra, B.G.; Pore, V.S. (2001). "Mifepristone (RU-486), the recently developed antiprogesterone drug and its analogues". Journal of the Indian Institute of Science. 81: 287–298.
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