Benzyl alcohol bimolecular

Normally, only a small stoichiometric excess (2-30 mol%) of silane is necessary to obtain good preparative yields of hydrocarbon products. However, because the capture of carbocation intermediates by silanes is a bimolecular occurrence, in cases where the intermediate may rearrange or undergo other unwanted side reactions such as cationic polymerization, it is sometimes necessary to use a large excess of silane in order to force the reduction to be competitive with alternative reaction pathways. An extreme case that illustrates this is the need for eight equivalents of triethylsilane in the reduction of benzyl alcohol to produce only a 40% yield of toluene the mass of the remainder of the starting alcohol is found to be consumed in the formation of oligomers by bimolecular Friedel-Crafts-type side reactions that compete with the capture of the carbocations by the silane.129... 

The reduction of acylcyanide using neat (f )-Alpine-Borane affords the corresponding (i )-P-amino alcohols [4cj. The reduction of acylcyanide and subsequent workup is not a straightforward process. The reaction of benzoylcyanide with neat Alpine-Borane (1.5 equiv) is complete within 2 h. The cyanohydrin-9-BBN adduct builds up to maximum, and then decreases with the appearance of a 9-BBN-benzyl alcohol adduct. Apparently, the 9-BBN-cyanohydrin adduct undergoes an elimination reaction to give benzaldehyde, which then undergoes reduction. The results indicate that the desired bimolecular reduction process can compete with the elimination reaction. 

An example of a bimolecular photoinitiator that generates free radicals by a hydrogen abstraction process is the combination of camphorquinone with a benzyl alcohol (equation [2.20]) [CRI 08], The carbon-centered free radical, 57, is capable of reducing a diaryliodonium salt in a similar manner to that shown previously in Diagram 2.5. 

To investigate functions of inorganic solids on bimolecular nucleophilic substitution reactions, zeolite and y-alumina were applied as promoters for accelerating the benzylation of alcohols, a familiar reaction for the protection of OH groups in alcohols (18) ... 

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