Interaction of alkoxides. XVIII. Utilitization of the complex base from alkyllithium and potassium alkoxides in the dimetallation of phenol, thiophenol, o-, m- and p-cresol

Article abstract of DOI:10.1016/0022-328X(90)85160-Z

Successful O- and ortho-ring metallation of phenol and side chain metallation in o-cresol has been achieved by use of a mixture of two molar equivalents of n-butyllithium, one molar equivalent of potassium t-butoxide and two molar equivalents of N,N,N',N'-tetramethylethylene diamine in hexane.Poor results were obtained with m-cresol, thiophenol and p-cresol. m-Cresol was effectively dimetallated with a mixture of two molar equivalents of ^tBuOK and two molar equivalents of ⁿBuLi*TMEDA.The effectiveness of another type of complex base based on 2-ethylhexyllithium (EhexLi) and potassium alkoxides has been also investigated, especially in respect of the influence of the concentration and the ctructure of the alkoxide used.With a complex base from EhexLi and 3 equivalents of potassium 3-methyl-3-pentoxide phenol was successfuly dimetallated even in the absence of TMEDA.Thus, the enhanced reactivity of a complex base containing a higher concentration of a more branched potassium alkoxide over that of previously used complex bases has been confirmed.