Chemical Properties
Sodium [bis(2-methoxyethoxy)]dihydridoaluminate (SDMA), NaAlH2(OCH2CH2OCH3)2, is a colorless, viscous liquid at room temperature that solidifies to a glass below 0 C; there is no sharp melting point. It is stable up to 170 C and decomposes above 214 C. At higher temperature decomposition is sudden and spontaneous. The presence of the two methoxyethoxy groups confers solubility not only in ethers but also in aromatic hydrocarbons. It is completely miscible with toluene at concentrations below 6 % and above 42 %. Viscous solutions of SDMA can be handled in contact with air, although atmospheric moisture causes hydrolysis.
Uses
Sodium bis(2-methoxyethoxy)aluminum hydride acts as a reducing agent in organic synthesis. It is used to prepare azoxyarenes, azoarenes and hydroazoarenes from nitroarenes. It plays an important role for the conversion of aldehydes, ketones, carboxylic acids, esters, acyl halides and anhydrides to primary alcohols. It is also employed in hydroaluminate alkenes and alkynes. It is utilized in the reduction of lactones and epoxides into diols. Further, it serves as a methylation reagent for aryl-activated compounds. In addition to this, it is involved in the reduction of amides, nitriles and amines to the corresponding amines.
Uses
Red-Al
? sodium bis(2-methoxyethoxy)aluminum hydride can be used as:
- A tosyl deprotecting agent.
- A catalyst for crosslinking of polyvinylsilanes (PVS) by Si-Si dehydrocoupling reaction in the presence of group 4 metallocene complexes.
- A reducing reagent for the synthesis of optically active N-protected amino alcohols and peptide alcohols.
Preparation
One method of preparation is
the controlled alcoholysis of NaAlH4 with 2-
methoxyethanol:
NaAlH4+2 CH3OCH2CH2OH→NaAlH2(OCH2CH2OCH3)2
+H2
On an industrial scale, however, it is produced
by direct synthesis from sodium, aluminum, and
2-methoxyethanol at 140 – 155 C in an atmosphere of hydrogen at at least 7 MPa:
Na+Al+2 CH3OCH2CH2OH→NaAlH2(OCH2CH2OCH3)2
The quantity of hydrogen required is generated in situ by the reaction of sodium and aluminum
with the alcohol. SDMA(Sodium bis(2-methoxyethoxy)aluminiumhydride) is marketed as a 70 %
solution in toluene (r = 1.036 g/cm3
) under the
name Vitride (Hexcel).
General Description
Red-Al
? sodium bis(2-methoxyethoxy)aluminum hydride [NaAlH
2(OCH
2CH
2OCH
3)
2] is used as a versatile reducing agent in organic synthesis. It is used to reduce:
- Aldehydes, ketones, esters, and anhydrides to primary alcohols.
- Ketoximes and aldoximes to primary amines.
- Cyclic compounds such as lactones and epoxides to diols.
It is also used as a catalyst in the ring-opening polymerization reactions.
