A new color of the synthetic chameleon methoxyallene: synthesis of trifluoromethyl-substituted pyridinol derivatives: an unusual reaction mechanism, a remarkable crystal packing, and first palladium-catalyzed coupling reactions

Chemistry : a European Journal
Oliver FlögelHans-Ulrich Reissig

Abstract

Addition of lithiated methoxyallene to pivalonitrile afforded after aqueous workup the expected iminoallene 1 in excellent yield. Treatment of this intermediate with silver nitrate accomplished the desired cyclization to the electron-rich pyrrole derivative 2 in moderate yield. Surprisingly, trifluoroacetic acid converted iminoallene 1 to a mixture of enamide 3 and trifluoromethyl-substituted pyridinol 4 (together with its tautomer 5). A plausible mechanism proposed for this intriguing transformation involves addition of trifluoroacetate to the central allene carbon atom of an allenyl iminium intermediate as crucial step. Enamide 3 is converted to pyridinol 4 by an intramolecular aldol-type process. A practical direct synthesis of trifluoromethyl-substituted pyridinols 4, 10, 11, and 12 starting from typical nitriles and methoxyallene was established. Pyridinol 10 shows an interesting crystal packing with three molecules in the elementary cell and a remarkable helical supramolecular arrangement. Trifluoromethyl-substituted pyridinol 4 was converted to the corresponding pyridyl nonaflate 13, which is an excellent precursor for palladium-catalyzed reactions leading to pyridine derivatives 14-16 in good to excellent yields. The ne...Continue Reading

Citations

Feb 28, 2015·Chemical Reviews·Liangbin HuangLukas J Gooßen
Dec 21, 2016·Chemistry : a European Journal·Hai-Bin Yang, Nicklas Selander
Feb 20, 2014·Chemical Society Reviews·Reinhold Zimmer, Hans-Ulrich Reissig
May 12, 2018·ChemSusChem·Sofie SeghersChristian V Stevens
Oct 24, 2007·Chemistry : a European Journal·Benito AlcaideMaría C Redondo
Apr 24, 2009·Chemistry : a European Journal·Tilman LechelHans-Ulrich Reissig
Jun 18, 2009·Chemistry : a European Journal·Jyotirmayee Dash, Hans-Ulrich Reissig
Jun 17, 2006·Chemical Communications : Chem Comm·Benito AlcaideMaría C Redondo
Oct 29, 2013·Chemical Communications : Chem Comm·Christopher B KellyNicholas E Leadbeater
Aug 26, 2016·Beilstein Journal of Organic Chemistry·Paul Hommes, Hans-Ulrich Reissig
May 28, 2011·Chemistry : a European Journal·Tilman LechelHans-Ulrich Reissig
Nov 8, 2013·Chemical Society Reviews·Marcus A Tius
Dec 1, 2007·Organic Letters·Jyotirmayee DashHans-Ulrich Reissig
Oct 17, 2008·Accounts of Chemical Research·Malte BrasholzReinhold Zimmer
Jul 12, 2008·Chemical Reviews·Jean-Marc WeibelPatrick Pale
Jan 12, 2013·Chemical Reviews·Anton V GulevichVladimir Gevorgyan
Jan 11, 2013·Organic Letters·Shivajirao L GholapHans-Ulrich Reissig

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