Reducing agents polymeric quaternary ammonium

Polymeric Quaternary Ammonium Borohydride Reducing Agents... 

A way to limit these reactions consists of replacing Li+ by a bulkier cation (quaternary ammonium, phosphonium, etc.) or by adding in the reaction medium, a solvating agent that increases the apparent radius of the lithium ion the attack of carbonyl groups by ion pairs can thus be thwarted, the probability of termination reduced, and the control of polymerization improved in this way. 

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