TITRATION OF ALKYLLITHIUMS WITH A SIMPLE REAGENT TO A BLUE END-POINT

Reaction of readily available N-benzylbenzamide (1) with a slight exce ss of BuLi produces a deep blue dianion. Under suitable conditions (TH F, -40 degrees C), 1 may be used as a stoichiometric reagent to titrat e n-BuLi, s-BuLi, and t-BuLi with good precision. Less reactive alkyll ithiums (MeLi and MeLi . LiBr), aryllithiums, and LDA may be titrated at higher temperatures (-20 to 0 degrees C). Titres are comparable to those obtained using the Gilman double titration method, and there app ears to be no interference from alkoxides. (C) 1997 Elsevier Science S .A.