Raab, V. and Kipke, J. and Gschwind, R. M. and Sundermeyer, J. (2002) 1,8-Bis(tetramethylguanidino)naphtalene (TMGN): a new superbasic and kinetically active „proton sponge. Chemistry - A European Journal 8 (7), pp. 1682-1693.
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1,8-Bis(tetramethylguanidino)naphthalene (TMGN, 1) is a new, readily accessible, and stable proton sponge with an experimental pKBH+ value of 25.1 in MeCN, which is nearly seven orders of magnitude higher in basicity than the classical proton sponge 1,8-bis(dimethylamino)-naphthalene (DMAN). Because of the sterically less crowded character of the proton-accepting sp2-nitrogen atoms, TMGN also has a higher kinetic basicity than DMAN, which is shown by time-resolved proton self-exchange reactions. TMGN is more resistant to hydrolysis and is a weaker nucleophile towards the alkylating agent EtI in comparison to the commercially available guanidine 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD). Crystal structures of the free base, of the mono- and bisprotonated base were determined. The dynamic behavior of all three species in solution was investigated by variable-temperature 1H NMR experiments. G values obtained by spectra simulation reveal a concerted mechanism of rotation about the C-N bonds of the protonated forms of TMGN.
|Institutions:||Chemistry and Pharmacy > Institut für Organische Chemie > Arbeitskreis Prof. Dr. Ruth Gschwind|
|Keywords:||basicity; NMR spectroscopy; peralkylated guanidines; protonation; proton sponges|
|Subjects:||500 Science > 540 Chemistry & allied sciences|
|Refereed:||Yes, this version has been refereed|
|Created at the University of Regensburg:||No|
|Deposited On:||11 Nov 2009 17:17|
|Last Modified:||11 Nov 2009 17:17|