Monoglyme is mainly used as inert special solvent for grignard-, reduction- and alkylation-reactions. It is very useful as inert solvent for organo metallic reactions in general, e.g reactions involving alkali metals such as lithium, sodium and potassium, Pd catalyzed couplings (Suzuki reaction - see below), Stille couplings of trialkyl tin derivatives, lithiations, Heck-and Ullmann reaction.
Monoglyme is a good solvent for Grignard reaction and offers an excellent alternative to diethyl ether and THF. However, we recommend butyl diglyme as a solvent for Grignards, as butyl diglyme is not miscible with water.
Monoglyme has a high solubility for Na/K alloy. Potassium is slightly soluble.
1.2-Dimethoxy ethane (Monoglyme) is an excellent functional solvent for the palladium (Pd) catalyzed carbon-carbon cross coupling of boronic acids with organic electrophiles like bromides, iodides and even chlorides (Suzuki coupling). A combination of Pd(PPh3)4 or PdCl2(PPh3)2 and aqueous sodium carbonate Na2CO3 in dimethoxy ethane works very well in most cases. Other useful bases include Et3N (triethyl amine) and CsCO3 (cesium carbonate). The coupling reaction proceeds more rapidly and with high yields under such homogeneous conditions. Even reactions of sterically hindered substrates like mesitylboronic acid are remarkably accelerated by using strong bases like aqueous barium hydroxide or aqueous sodium hydroxide in dimethoxy ethane as a solvent (homogeneous reaction). |
This article (N. Kataoka et al, J. Org. Chem, 2002, 67,(16) 5553-5566) lists many examples and standard procedures for Pd catalyzed coupling reactions, such as couplings of aryl halides with amines using "DME" (Monoglyme) as a solvent and K2CO3 or Cs2CO3 as base. This solvent / base combination gives excellent yields for base sensitive substrates like esters, etc.
Monoethylene glycol dimethyl ether forms chelate complexes with cations and acts as a bidentate ligand. This leaves anions active, so that for reactions like anionic polymerizations, nucleophilic substitutions and metal hydride reactions dimethoxyethane can significantly enhance reaction rates.
Monoglyme is a good solvent for different kinds of oligo- and polysaccharides and is frequently used in sugar / carbohydrate chemistry.
Dimethoxyethane is also used as solvent for electrolytes of lithium batteries and as process solvent for the recycling of Li-batteries.
Monoglyme is used in a process for the surface treatment of aluminium in order to make aluminium resistant against chemicals.
Its outstanding stability even at high pH values makes it an excellent solvent for reactions with strong bases.
The low boiling point (85°C) of Monoglyme and its high stability allow for easy separation from reaction mixtures and recovery. |
Further applications involving Monoglyme as a solvent (external websites open in a new window):
- Selective solvent for Favorskii reactions
- Solvent for Stille couplings ("DME" = dimethoxy ethane = mono glyme)
- Chromium electroplating
- Cyanoacrylate based adhesives solvent
- Solvent for alkali metal dispersions used for etching of teflon (polytetrafluoro ethylene)
- Process solvent for manufacture of anti-hiv drugs
- Activator of borohydrides
- Solvent for birch reductions
- Solvent for lithiations (eg. with methyllithium to prepare lithium enolates from enol acetates)
- Solvent for the generation of lithium dialkylcuprates.
- Solvent for reductive carbonyl coupling reactions with titanium (III) chloride TiCl3 and lithium (zinc) or with TiCl4 to alkenes - McMurry reaction. (e.g., ring formation reaction yielding an indole system or synthesis of adamantylidene adamantane
- Solvent for lithiation of carboxylic acids with lithium hydryde (LiH) to prepare methyl ketones from carboxylic acid
- Monoglyme significantly enhances the polymerisation rate in ring opening polymerizations of caprolactone
- Selective solvent for nucleophilic aromatic substitutions of nitro-chloro-benzenes.
- Solvent for Simmons-Smith reaction (addition of carbene to double bond, formation of cyclopropanes) e.g., preparation of 3-phenylcyclopropyl methanol
- Reduction of tin-halides to tin-hydrides with sodium borohydride, e.g preparation of a water soluble tin hydride
- Sugar chemistry: protection of OH-groups with 2,2-dimethoxypropane (acetone dimethylketal) and stannous chloride SnCl2, e.g., preparation of glyceraldehyde acetonide from mannitol.
- Dehydrations of substituted formamides with phosphorus oxychloride (POCL3) to produce isocyanides, e.g., preparation of tolylsulfonylmethyl isocyanide
- Acid catalyzed condensation of furan with ketones accelerated by lithium perchlorate in monoglymee, e.g., condensation of furan with acetone
- Carboxylation of aromatic compounds: preparation of ferrocenecarboxylic acid involving potassium-tert-butoxide tert-BuOK
- Directed Aldol condensations (NaH reduction followed by lithiation in Monoglyme) |