Diglyme

Diethylene glycol dimethyl ether

C6H14O3

MW: 134.1

CAS: 111-96-6

Like Monoglyme, Diglyme is used as inert special solvent for grignard-, reduction- and alkylation-reactions, organo metallic reactions in general, reactions involving alkali metals such as lithium, sodium and potassium. Diglyme has a high solubility for Na/K alloy. Potassium is sparingly soluble. Diglyme is used as safe solvent for lithium aluminium hydride (LiAlH4).

Diglyme accelerates NaBH4 reductions and allows for high temperature reactions.

Diglyme 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.

Diethylene glycol dimethyl ether acts as chelate ligand for cations. This leaves anions active, so that for reactions like anionic polymerizations, nucleophilic substitutions and metal hydride reactions Diglyme can significantly enhance reaction rates.

Its outstanding stability even at high pH values makes it an excellent solvent for reactions with strong bases.

The boiling point of 162°C and the outstandig stability of Diglyme allows for easy separation from reaction mixtures and almost quantitative recovery.

Further applications:

- Selective reduction of acid chlorides to aldehydes with lithium aluminium tri-tert-butoxyhydride LiAlH(O-t-Bu)₃. [Cf. H. C. Brown and B. C. Subba Rao, J. Am. Chem. Soc., 80, 5377 (1958)]

- Selective solvent for the methanolysis of 1,3,5-trichlorobenzene with sodium methoxide to 1-chloro-3,5-dimethoxybenzene

- General method for the preparation of substituted perfluoroolefins in diglyme (conversion of ketone >C=O to difluoroethene >C=CF₂)

- Cosolvent for copper catalyzed halogen exchange reaction (Halex reaction) Ar-Br -> Ar-I

- Process solvent for manufacture of anti-hiv drugs

- Activator of borohydrides - solvent for sodium borohydride and borane reductions (e.g., preparation of perhydro-9b-boraphenalene, preparation of 3-pinanamine from a-pinene)

- Solvent for sodium azide (NaN₃) (e.g., preparation of trimethylsilyl azide from chlorotrimethylsilane)

- Safe solvent for the preparation of highly active magnesium for Grignard reactions from magnesium chloride and potassium

- Solvent for raney nickel e.g., preparation of biaryls from arenes involving organotellurium compounds avoiding halogenated precursors

- Preparation of ketene acetals: reaction of vinylidene chloride with alcoholates

- Solvent for reductions or isomerisations with lithium tetrahydrido aluminate (III) LiAlH₄

- Solvent for regioselective lithiations (e.g., of thiophene and thiophene derivatives)

- Solvent for birch reductions

- Separation of binary water / acetone mixtures by extractive ternary distillation using diglyme as entrainer. Acetone with 99.9% purity is obtained.

- Solvent for diborane reactions (anti-Markovnikov hydroboration-oxidation to make alcohols from olefins)

- Solvent for the preparation of Ferrocene

- Diglyme is used as solvent for battery electrolytes.

- Inert solvent for the reaction of ethine (acetylene) with sodium hydroxide, NaOH (deprotonation). Subsequent reaction with a ketone yields hydroxy-ethines (ethinyl carbinols). "Ethinylation".

- Solvent for elimination of hydrofluoric acid from perfluorinated compounds (dehydrofluorination) with potassium hydroxide, KOH. Better yields than standard solvents like EtOH.

- Preparation of CF₃SiCl₃ from CF₃Br, HSiCl₃ and NR₃

- Solvent for Teflon (poly tetrafluoro ethylene) etchants

Synonyms: Bis(2-methoxyethyl)ether, dimethyl diglycol, dimethoxy diethyleneglycol, diethylene glycol dimethyl ether, DEGDME, DMDG, 2,5,8-trioxanonane. CAS# 111-96-6