title: Removal of the pyridine directing group from α-substituted N-(pyridin-2-yl)piperidines obtained via directed Ru-catalyzed sp3 C-H functionalization.
abstract: Two strategies, "hydrogenation-hydride reduction" and "quaternization-hydride reduction", are reported that make use of mild reaction conditions (room temperature) to efficiently remove the N-pyridin-2-yl directing group from a diverse set of C-2-substituted piperidines that were synthesized through directed Ru-catalyzed sp(3) C-H functionalization. The deprotected products are obtained in moderate to good overall yields irrespective of the strategy followed, indicating that both methods are generally equally effective. Only in the case of 2,6-disubstituted piperidines, could the "quaternization-hydride reduction" strategy not be used. The "hydrogenation-hydride reduction" protocol was successfully applied to trans- and cis-2-methyl-N-(pyridin-2-yl)-6-undecylpiperidine in a short synthetic route toward (±)-solenopsin A (trans diastereoisomer) and (±)-isosolenopsin A (cis diastereoisomer). The absolute configuration of the enantiomers of these fire ant alkaloids could be determined via VCD spectroscopy.
authors.affiliation: Organic Synthesis, Department of Chemistry, University of Antwerp , Groenenborgerlaan 171, 2020 Antwerp, Belgium.
authors.forename: Veerle
authors.initials: V
authors.lastname: Smout
authors.forename: Aldo
authors.initials: A
authors.lastname: Peschiulli
authors.forename: Stefan
authors.initials: S
authors.lastname: Verbeeck
authors.forename: Emily A
authors.initials: EA
authors.lastname: Mitchell
authors.forename: Wouter
authors.initials: W
authors.lastname: Herrebout
authors.forename: Patrick
authors.initials: P
authors.lastname: Bultinck
authors.forename: Christophe M L
authors.initials: CM
authors.lastname: Vande Velde
authors.forename: Didier
authors.initials: D
authors.lastname: Berthelot
authors.forename: Lieven
authors.initials: L
authors.lastname: Meerpoel
authors.forename: Bert U W
authors.initials: BU
authors.lastname: Maes
mesh_terms: D000470:Alkaloids / Q000737:chemistry*; D002384:Catalysis; D006865:Hydrogenation; D015394:Molecular Structure; D010880:Piperidines / Q000737:chemistry*; D011725:Pyridines / Q000737:chemistry*; D012428:Ruthenium / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D000470:Alkaloids; D010880:Piperidines; D011725:Pyridines; C002351:Solenopsin A; D012428:Ruthenium; C023666:pyridine