Sodium bis(trimethylsilyl)amide

Description

Sodium bis(trimethylsilyl)amide (NaHMDS) is a strong base. It is commercially available as a solid and as a solution in a variety of solvents (ex. THF, toluene, and MTBE). Similar reagents include lithium bis(trimethylsilyl)amide (LiHMDS) and potassium bis(trimethylsilyl)amide (KHMDS).

Chemical properties

Slightly yellow to light beige crystalline powder

Physical properties

mp 171–175 °C; bp 170 °C/2 mmHg.

The Uses of Sodium bis(trimethylsilyl)amide

Sodium bis(trimethylsilyl)amide is a synthetically useful reagent in that it combines both high basicity and nucleophilicity, each of which may be exploited for useful organic transformations such as selective formation of enolates, preparation of Wittig reagents, formation of acyl anion equivalents, and the generation of carbenoid species. As a nucleophile, it has been used as a nitrogen source for the preparation of primary amines.It is useful as a sterically hindered base and as a nucleophile.

The Uses of Sodium bis(trimethylsilyl)amide

To a solution of the indole (A) (0.300 g, 0.92 mmol) in THF (30 mL) was added NaHMDS (1 M in THF, 0.93 mL, 0.93 mmol) at -78 C. The mixture was stirred at -78 C for 20 min, then at RT for 1 h. The alkyl chloride (B) (171 mg, 1.86 mmol) was added, and the reaction mixture was stirred at RT for another 18 h. The mixture was quenched with ice-H2O and extracted with EtOAc (3 x 30 mL). The combined organics were dried (Na2SO4) and concentrated to provide the product which was used in the next step without further purification. [0.300 g, 84%]

The Uses of Sodium bis(trimethylsilyl)amide

It is a strong base; deprotonates ketones and esters to generate enolate derivative.

The Uses of Sodium bis(trimethylsilyl)amide

Significantly accelerated the polymerization of pheneylacetylene in conjunction with rhodium (I) catalysis

General Description

Sodium bis(trimethylsilyl)amide solution (NaHMDS) is widely used as a strong base in organic synthesis for deprotonation reactions and base-catalyzed reactions. It is also involved in the generation of enolates, Wittig reagents and carbenes.

Purification Methods

It can be sublimed at 170o/2mm (bath temperature 220-250o) onto a cold finger, and can be recrystallised from *C6H6 (its solubility is: 10g in 100mL at 60o). It is slightly soluble in Et2O and is decomposed by H2O. [Wannagat & Niederprüm Chem Ber 94 1540 1961.]It is available commercially under N2 in Sure/Seal bottles in tetrahydrofuran (various concentrations) and at ~0.6M in toluene. [Beilstein 4 IV 4014.]