Diphenylsilane-Cesium Fluoride

Ph2SiH2-CsF
Ph2SiH2

[775-12-2]  · C12H12Si  · Diphenylsilane-Cesium Fluoride  · (MW 184.33) CsF

[13400-13-0]  · CsF  · Diphenylsilane-Cesium Fluoride  · (MW 151.91)

(reagent for the reduction of aldehydes,1,2 ketones,1,2 and esters;3 selective 1,2-reduction of enones2,4 and enals2,4)

Physical Data: Ph2SiH2: bp 95-97 °C; d 0.993 g cm-3. CsF: mp 683 °C.

Solubility: Ph2SiH2: sol THF. CsF: sol H2O; slightly sol THF, MeCN.

Form Supplied in: Ph2SiH2: clear liquid; widely available. CsF: white solid; widely available. Drying: anhydrous CsF is prepared by flame drying under vacuum, taking care not to fuse the salt.

Handling, Storage, and Precautions: Ph2SiH2 should be used in a fume hood.

Carbonyl Reduction.

The Ph2SiH2-CsF reagent can reduce neat aldehydes and ketones to alcohols at 25 °C in <30 min1,2 (eq 1), though Triethoxysilane activated with either Cesium Fluoride or Potassium Fluoride is generally a better reagent for these solvent-free reductions.4

Esters can be reduced to alcohols with Ph2SiH2-CsF at elevated temperatures in 65-90% yield; however, the more reactive silane (EtO)3SiH with CsF activation will do the reduction at 25 °C.3 Several enones and enals undergo selective 1,2-reduction with Ph2SiH2-CsF2,4 (eq 2), although cyclohexenone reduction is not as selective and there is a tendency for overreduction to cyclohexanol to occur.2

Related Reagents.

Phenylsilane-Cesium Fluoride; Triethoxysilane; Triethylsilane.


1. Boyer, J.; Corriu, R. J. P; Perz, R.; Reye, C. JOM 1978, 148, C1. (CA 1978, 89, 23 216b).
2. Boyer, J.; Corriu, R. J. P; Perz, R.; Reye, C. JOM 1979, 172, 143. (CA 1979, 91, 108 039n).
3. Boyer, J.; Corriu, R. J. P.; Perz, R.; Poirier, M.; Reye, C. S 1981, 558.
4. Corriu, R. J. P.; Perz, R.; Reye, C. T 1983, 39, 999.

Thomas J. Fleck

The Upjohn Company, Kalamazoo, MI, USA



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