Diphenylsilane-cesium fluoride

Oxazoline Formation. The PhSiHs-cesium fluoride reagent is a nonnucleophilic hydride donor without Lewis acid character with characteristics similar to the diphenylsilane-cesium fluoride, a-NaphSiHs-CsF, and (RO)3SiH-CsF reagents on which it is based. In aprotic solvents, it has been used to reduce 4-oxazolium salts to 4-oxazolines. The 4-oxazolines open at —40 ° C to azomethine ylides, which are trapped with dipo-larophiles to give 3-p3rrolines (2) (eq 1). For isolation purposes... 

Related Reagents. (2-Dimethylaminomethylphenyl)phenyl-silane diphenylsilane-cesium fluoride phenylsilane-cesium fluoride triethylsilane triphenylsilane. 

Diphenylsilane reacts with two equivalents of neat n-heptanal in the presence of anhydrous cesium fluoride within three minutes at room temperature to form di-n-hep toxy diphenylsilane quantitatively (Eq. 162).319 Potassium fluoride and potassium phthalate are considerably less effective promoters, even at temperatures up to 140°.319... 

Diphenylsilane catalyzed by various salts promotes the 1,2-reduction of cinnamaldehyde.318 Cesium fluoride catalysis is particularly effective.320 It is possible to stop these reactions at the silyl ether stage.73,320 The 1,2-reduction of citral is accomplished in high yield with diphenylsilane and Wilkinson s catalyst (Eq. 262) 435 Interestingly, the trialkylsilanes, ethyldimethylsilane and triethylsilane, give high yields of the 1,4-reduction product whereas diisopropylsilane gives a 1 1 mixture of 1,2- and 1,4-reduction (Eq. 263)435... 

The 1,4-reduction of a,/3-unsaturated aldehydes is best carried out with diphenylsilane in the presence of zinc chloride and tetrakis(triphenylphosphine) palladium436 or a combination of triethylsilane and tris(triphenylphosphine) chlororhodium 437 Other practical approaches use phenylsilane with nickel (0) and triphenylphosphine438 and diphenylsilane with cesium fluoride.83 It is possible to isolate the initial silyl enol ether intermediate from the 1,4-hydrosilylation of o, /3-unsaturated aldehydes (Eq. 264).73,411 The silyl enol ethers are produced as a mixture of E and Z isomers. 

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