Nuclear magnetic resonance (NMR) spectroscopy: A review and a look at its use as a probative tool in deamination chemistry

This year (2006) represents the 60th anniversary of nuclear magnetic resonance (NMR) spectroscopy (discovered independently by Nobel laureates Edward Purcell and Felix Bloch). It is therefore appropriate and indeed valuable to reflect on how this versatile methodology has developed, expanded, and evolved into a cornerstone of chemical research since 1946. No doubt multiple reviews discussing various aspects of NMR technology will emerge over the course of this year, but the field has grown so exponentially since its inception that it would be impossible for a single review to meaningfully encompass all features of the NMR methodology. This work, therefore, is not meant to provide a comprehensive review of NMR spectroscopy (such an undertaking would prove unwieldy and is inapt in the current context). Instead, it will provide an overview of NMR spectroscopy including the basic principles of NMR (the NMR phenomenon, instrumentation, and spectral interpretation) the historical development of the field, and a few unique applications of the methodology. Finally, illustrations of the utility and application of NMR spectroscopy as a probative tool in the intriguing field of deamination chemistry will be examined. Among the examples highlighted are the elucidation of the mechanism of N-nitrosoamide conversion to the trans-diazotate ester, denitrosation under near-neutral conditions, elucidation of the bond-forming step of Friedel-Crafts benzylation, and the identification of novel electronic (π*-acceptor agostic-type interaction) and steric (persisteric) effects.