Phosphonium salts dealkylation

In the reactions characterized in the general sense above, phenyl and benzyl were the organic residues bound to phosphorus. It is not clear which of these groups is removed in the LAH dealkylation step. It should also be noted that as tetraquaternary phosphonium salts, these species do not qualify as crown analogs in the strictest sense because of the absence of lone pair electrons on phosphorus. Furthermore, the quaternary phosphorus can resist oxidation much better than secondary or tertiary phospho-... 

Another series of reactions (Nos 8-15) show different possibilities for the addition of conjugated double bonds on a P(III) atom. Although this type of reaction has been stated to be a concerted six-electron dissociative process, and therefore stereoselective, its scope is limited by the fact that it cannot be generalized to all P(III) compounds as some of them are fairly unreactive, or yield phosphonium salts or may even be dealkylated. 

Phosphonium salts can be dealkylated by treatment with alkoxides to yield alkanes. Although the hydrolytic cleavage of phosphonium salts in solution has been well investigated, the solid-phase variant of this reaction has not yet found broad application. One example, in which traceless linking was based on the alkoxide-induced dealkylation of a resin-bound phosphonium salt, is given in Table 3.48 (Entry 1). 

Dealkylation of phosphonium salts 83 is promoted by NaOH, and isomeric phosphabicyclononanes 84 are readily separated by a sequence of hydrophosphination/dehydrophosphination steps <1997CC1527> (Equation 8). Decomposition of phosphonium salt 85 with NaOH/ethylene glycol resulted in the elimination of toluene and bicyclic compound 86 <1996RJC567> (Equation 9). 

Aminophosphines, phosphinites and phosphonites from quasi-phosphonium salts with alkyl halides in normal 5 n reactions. The aminophosphonium salts and the salts derived from aryl phosphinites and diaryl phosphonites are stable, but the majority of the quasi-phosphonium salts which contain alkoxy groups are dealkylated during the reaction with the alkyl halide (the Arbuzov reaction, see below). Thio analogues of phosphinites and... 

Quaternary phosphonium salts are generally stable crystalline solids which have high solubility in polar solvents. They are relatively stable towards dealkylation but hydrolyze in the presence of hydroxide ion to the phosphine oxides ... 

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