[996-50-9] · C7H19NSi · Trimethylsilyldiethylamine · (MW 145.36)
Physical Data: bp 127-129 °C; d 0.767 g cm-3; n
Solubility: sol pentane, hexane, acetonitrile, ether, THF, acetone.
Form Supplied in: liquid; commercially available.
Analysis of Reagent Purity: NMR, GC.
Handling, Storage, and Precautions: stable indefinitely when maintained in a dry environment; destroyed by water.
The major use of this reagent has been in the protection of functional groups (particularly hydroxyl) as the trimethylsilyl derivatives. This is illustrated in work on brefeldin A (eq 1)7 and in the synthesis of prostaglandin E2 methyl ester (eq 2), where selective protection of two hydroxyl groups occurred.2 In addition, axial alcohols are converted into trimethylsilyl ethers much faster than equatorial alcohols.8 Another multifunctional molecule which has been protected is the alcohol produced by cleaving the enone shown in eq 3.9
Unsaturated g-butyrolactones are converted into 2-silyloxyfurans,10 while the corresponding N-methyllactams give trimethylsilyloxypyrroles.11 Amines can be converted into trimethylsilyl derivatives, as in the case of putrescine which forms the N,N´-bis(trimethylsilyl) compound in 95% yield.12 Carboxylic acids can be silylated, as in the case of amino acid hydrochloride salts in DMF.13 The hydroxyl group of acid-sensitive compounds, such as that in eq 4, can be protected so that conversion to the phosphoryl chloride moiety gives trimethylsilyl chloride instead of HCl as a byproduct, thus enabling the other groups to survive.14
The diethylamino group can be transferred to electrophilic compounds. Oxalyl Chloride is converted into the monoamide with 1 equiv of TMSNEt2 at -23 °C and the bisamide with excess silylamine at room temperature;2 Benzeneselenenyl Chloride gives the selenenamide.15 Unsaturated lactones give b-diethylamino lactones with TMSNEt2 and a trace of diethylamine.10 Conjugated enones give b-amino enol silyl ethers (eq 5),16 while 1-triphenylsilylpropynone gives simple conjugate addition of diethylamine.17
Harold W. Pinnick
Bucknell University, Lewisburg, PA, USA