Silylation

From Wikipedia, the free encyclopedia
  (Redirected from Desilylation)
Jump to: navigation, search

Silylation is the introduction of a (usually) substituted silyl group (R3Si) to a molecule. The process is the basis of organosilicon chemistry.

Silylation of organic compounds[edit]

Alcohols, carboxylic acids, amines, thiols, and phosphates can be silylated. The process involves the replacement of a proton with a trialkylsilyl group, typically trimethylsilyl (-SiMe3). Generally the substrate is deprotonated with a suitable strong base followed by treatment with a silyl chloride (e.g. trimethylsilyl chloride). Often strong bases such butyl lithium or a Grignard reagent are used, as illustrated by the synthesis of a trimethylsilyl ethers as protecting groups from an alcohol:

ROH + BuLi → ROLi + BuH
ROLi + Me3SiCl → ROSiMe3 + LiCl

Silyl derivatives are generally less polar and more thermally stable than their precursor organic compound. The introduction of a silyl group(s) gives derivatives of enhanced volatility, making the derivatives suitable for analysis by gas chromatography and electron-impact mass spectrometry (EI-MS). For EI-MS, the silyl derivatives give more favorable diagnostic fragmentation patterns of use in structure investigations, or characteristic ions of use in trace analyses employing selected ion monitoring and related techniques.[1]

Desilylation[edit]

Desilylation is the reverse of silylation: the silyl group is exchanged for a proton. Various fluoride salts (e.g. sodium, potassium, tetra-n-butylammonium fluorides) are popular for this purpose.[2][3]

ROSiMe3 + F- + H2O → ROH + FSiMe3 + OH-

Silylation of metals[edit]

CpFe(CO)2Si(CH3)3, a trimethylsilyl complex.

Coordination complexes with silyl ligands are well known. An early example is CpFe(CO)2Si(CH3)3. Metal silyl complexes are important intermediates in hydrosilation, a process used to make organosilicon compounds.[4]

See also[edit]

References[edit]

  1. ^ http://www.sigmaaldrich.com/analytical-chromatography/analytical-reagents/derivatization-reagents/silylation.html
  2. ^ Mercedes Amat, Sabine Hadida, Swargam Sathyanarayana, and Joan Bosch "Regioselective Synthesis of 3-Substituted Indoles: 3-Ethylindole" Organic Syntheses 1997, volume 74, page 248. doi:10.15227/orgsyn.074.0248
  3. ^ Nina Gommermann and Paul Knochel "N,N-Dibenzyl-n-[1-cyclohexyl-3-(trimethylsilyl)-2-propynyl]-amine from Cyclohexanecarbaldehyde, Trimethylsilylacetylene and Dibenzylamine" Organic Syntheses 2007, vol. 84, page 1. doi:10.15227/orgsyn.084.0001
  4. ^ Moris S. Eisen "Transition-metal silyl complexes" in The Chemistry of Organic Silicon Compounds. Volume 2 Edited by Zvi Rappoport and Yitzhak Apeloig, 1998, John Wiley & Sons.

External links[edit]