1,2-BIS[(DIMETHYLAMINO)DIMETHYLSILYL]ETHANE

Physical properties

bp 100–103°C/13 mmHg; d 0.824 g cm?3.

Uses

1,4-Bis(dimethylamino)-1,1,4,4-tetramethyldisilethylene is used as a reagent for the protection of primary amines with lower pKa values, such as substituted anilines, as their tetramethyldisilylazacyclopentane or Stabase adduct; precursor of tetramethyldisilylthiacyclopentane, a sulfur transfer reagent.
The title reagent is used for the preparation of Stabase derivatives of primary amines, and is particularly useful for the protection of primary aromatic amines with pKa values of 10–11. The protection of substituted anilines is achieved by heating equimolar amounts of the title compound and the anilines in the presence of zinc iodide (0.5 mol %) under a slow stream of nitrogen at 140°C for 5 h. In many cases the products can be purified by vacuum distillation. Cleavage of the Stabase adducts to the corresponding primary amines can be performed in ether in the presence of 2 equiv of methanol and a small amount of p-toluenesulfonic acid monohydrate (0.2 mol %). The tetramethyldisilylazacyclopentane or Stabase adduct (3) is a particularly attractive protecting group due to its ease of preparation, base stability, and facile removal (eq 1).

Preparation

the reagent is prepared as a colorless liquid in 90% yield by treating commercially available bis(chlorodimethylsilyl) ethane with 5 equiv of dimethylamine in ether at 0°C for 5 h.