Trimethylsilyl iodide explained

Trimethylsilyl iodide (iodotrimethylsilane or TMSI) is an organosilicon compound with the chemical formula (CH₃)₃SiI. It is a colorless, volatile liquid at room temperature.

Preparation

Trimethylsilyl iodide may be prepared by the oxidative cleavage of hexamethyldisilane by iodine^[1] or by the cleavage of hexamethyldisiloxane with aluminium triiodide.

TMS-TMS + I₂ → 2 TMSI (TMS = (CH₃)₃Si)

3 TMS-O-TMS + 2 AlI₃ → 6 TMSI + Al₂O₃

Applications

Trimethylsilyl iodide is used to introduce the trimethylsilyl group onto alcohols (ROH):

R-OH + TMSI → R-OTMS + HI

This type of reaction may be useful for gas chromatography analysis; the resultant silyl ether is more volatile than the underivatized original materials.^[2] However, for the preparation of bulk trimethylsilylated material, trimethylsilyl chloride may be preferred due to its lower cost.

TMSI reacts with alkyl ethers (ROR′), forming silyl ethers (ROSiMe₃) and iodoalkanes (RI) that can be hydrolyzed to alcohols (ROH).^[3]

Trimethylsilyl iodide is also used for the removing of the Boc protecting group,^{[4] [5]} especially where other deprotection methods are too harsh for the substrate.^[6]

References

1. 10.1016/0040-4020(82)87002-6 . Iodotrimethylsilane—a versatile synthetic reagent. 1982 . Olah . G . Narang . S. C. . Tetrahedron . 38 . 15 . 2225.
2. Web site: GC/MS Analysis for Morphine and Other Opiates in Urine.
3. Michael E. Jung . Mark A. Lyster . Quantitative dealkylation of alkyl ethers via treatment with trimethylsilyl iodide. A new method for ether hydrolysis . . 42 . 23 . 1977 . 3761–3764 . 10.1021/jo00443a033.
4. Michael E. Jung . Mark A. Lyster . Conversion of alkyl carbamates into amines via treatment with trimethylsilyl iodide . . 7 . 1978 . 315–316 . 10.1039/C39780000315.
5. Richard S. Lott . Virander S. Chauhan . Charles H. Stammer . Trimethylsilyl iodide as a peptide deblocking agent . . 11 . 1979 . 495–496 . 10.1039/C39790000495.
6. Zhijian Liu . Nobuyoshi Yasuda . Michael Simeone . Robert A. Reamer . N-Boc Deprotection and Isolation Method for Water-Soluble Zwitterionic Compounds . . 2014 . 79 . 23 . 11792–11796 . 10.1021/jo502319z. 25376704 .