Organosilane Reduction of Alkenes

Supplemental References for Table 1. Organosilane Reduction of Alkenes... 

A catalyst, usually acid, is required to promote chemoselective and regioselective reduction under mild conditions. A variety of organosilanes can be used, but triethylsilane ia the presence of trifiuoroacetic acid is the most frequendy reported. Use of this reagent enables reduction of alkenes to alkanes. Branched alkenes are reduced more readily than unbranched ones. Selective hydrogenation of branched dienes is also possible. 

The ionic hydrogenation of carbon-carbon multiple bonds has been demonstrated only for the reduction of carbon-carbon double bonds which on protonation result in the formation of tertiary, or aryl-substituted, carbocations. The ability to use this reduction reaction with functionally substituted alkenes will be limited to those systems that do not contain functional groups that would otherwise react with trifluo-roacetic acid or the organosilane. 

Ally halides (equation 37), vinyl halides (equation 38) and vinyl ethers are good substrates for the preparation of organosilanes having functional groups at the 3- or 7-position. Reduction of these substrates sometimes takes place to give the parent alkenes (equation 37), which are derived from 3-elimi-nation of the regioisomeric hydrosilylation intermediates. ... 

In contrast to the typical palladium(0)-catalyzed cross-coupling reaction of vinyl triflates with organosilanes, this is an example of the reduction of an enone to an alkene by transfer of a proton instead of an alkyl moiety/ ... 

The most common reduction system for the ionic hydrogenation of double bonds is trifluoroacetic acid with an organosilane. The alkene must be capable of undergoing protonation by trifluoroacetic acid which limits the application of this reaction to the reduction of tri-and tetrasubstituted alkenes, as well as aryl-substituted alkenes. 

---