A solid-state, solution, and theoretical structural study of kinetic and thermodynamic lithiated derivatives of a simple diazomethane and their reactivities towards aryl Isothiocyanates

Reference:

Armstrong, D. R., Davies, R. P., Haigh, R., Hendy, M. A., Raithby, P. R., Snaith, R. and Wheatley, A. E. H., 2003. A solid-state, solution, and theoretical structural study of kinetic and thermodynamic lithiated derivatives of a simple diazomethane and their reactivities towards aryl Isothiocyanates. European Journal of Inorganic Chemistry

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Abstract

(Trimethylsilyl)diazomethane (1-H) reacts with nBuLi in THE at elevated temperature to afford (previously reported) 1-Li.(3)/2THF. However, reaction in hexane/TMEDA at low temperature affords instead the N-lithiate Me3SiCNNLi-TMEDA (9), which is a novel "open" pseudo-cubic tetramer in the solid state. Variable-temperature NMR spectroscopy suggests that N-metallated 9, apparently the kinetic product of the reaction, irreversibly rearranges at high temperature in solution to give the thermodynamically preferred C-lithiated isomer. These observations, supported by DFT calculations, influence our understanding of the reactivity of lithiated di-azomethanes towards aryl isothiocyanates, suggesting as they do that previously observed product selectivity in these reactions is critically dependent on temperature control exercised during the process. (C) Wiley-VCH Verlag GmbH Co.

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