15191-27-2Relevant articles and documents
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Goessmann
, p. 20 (1906)
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Ligand-controlled regiodivergent nickel-catalyzed annulation of pyridones
Donets, Pavel A.,Cramer, Nicolai
, p. 633 - 637 (2015/03/04)
The 1,6-annulated 2-pyridone motif is found in many biologically active compounds and its close relation to the indolizidine and quinolizidine alkaloid core makes it an attractive building block. A nickel-catalyzed C-H functionalization of 2-pyridones and subsequent cyclization affords 1,6-annulated 2-pyridones by selective intramolecular olefin hydroarylation. The switch between the exo- and endocyclization modes is controlled by two complementary sets of ligands. Irrespective of the ring size, the regioselectivity during the cyclization is under full catalyst control. Simple cyclooctadiene promotes an exo-selective cyclization, whereas a bulky N-heterocyclic carbene ligand results in an endoselective mode. The method was further applied in the synthesis of the lupin alkaloid cytisine.
Total synthesis of (±)-cytisine
O'Neill, Brian T.,Yohannes, Daniel,Bundesmann, Mark W.,Arnold, Eric P.
, p. 4201 - 4204 (2007/10/03)
(equation presented) The nicotine partial agonist cytisine was prepared in five steps featuring an "in situ" Stille or Suzuki biaryl pyridine coupling. Differentiation of the pyridyl rings was accomplished via selective benzylation and then reduction of a pyridinium ring. The penultimate diazabicyclo[3.3.1]-nonane intermediate was obtained with high diastereoselectivity. A similar sequence has been employed for the synthesis of novel derivative 9-methoxycytisine.