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).
