Sn2 reactions with tetralkylammonium salts

The Sn2 reaction of triphenylphosphine with triethylbenzylammonium chloride (the tertiary amine is thus the leaving group) was studied under solvent-free microwave conditions. The reaction occurred only under the action of MW [83] irradiation (Eq. 53). 

This effect is readily attributable to the very loose structure of the ion pairs in the TS (additionally involving delocalization in the phenyl groups of the phosphine) and which are therefore far more polar than the initial ion pairs in the GS. 

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