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Selectfluor-Mediated Dialkoxylation of Tungsten η2-Pyridinium Complexes

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journal contribution
posted on 26.01.2009 by George W. Kosturko, Daniel P. Harrison, Michal Sabat, William H. Myers, W. Dean Harman
η2-coordinated pyridinium complexes of {TpW(NO)(PMe3)} undergo a stereoselective dialkoxylation reaction when treated with Selectfluor in an alcohol. The alkoxy groups add to the 5- and 6-positions in a syn fashion (proven by X-ray diffraction). When the N-acetylpyridinium complex is dialkoxylated, the resulting acyldihydropyridinium system readily undergoes nucleophilic addition with cyanide ion to stereoselectively generate a third stereocenter at C2 of the pyridine ring. Treatment with CAN decomplexes the tetrahydropyridine.