title: Intramolecular cyclization manifolds of 4-alkylpyridines bearing ambiphilic side chains: construction of spirodihydropyridines or benzylic cyclization via anhydrobase intermediates.
abstract: 4-Alkylpyridines possessing nucleophilic β-dicarbonyl side chains have been converted to spirodihydropyridines upon treatment with ethyl chloroformate and sub-stoichiometric amounts of Ti(O(i)Pr)(4). Alternatively, inclusion of mild base in the reaction medium was found to facilitate generation of anhydrobase intermediates. Subsequent aldol-like condensations with electrophilic side chain moieties followed by hydrolysis delivered benzylically cyclized pyridines in good yield. In situ hydrogenation of cyclized anhydrobase intermediates afforded 4-substituted piperidines.
authors.affiliation: Department of Chemistry, University of Iowa, Iowa City, Iowa 52242, USA.
authors.forename: Sharavathi G
authors.initials: SG
authors.lastname: Parameswarappa
authors.forename: F Christopher
authors.initials: FC
authors.lastname: Pigge
mesh_terms: D003500:Cyclization; D006865:Hydrogenation; D006868:Hydrolysis; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D011725:Pyridines / Q000737:chemistry*; D013141:Spiro Compounds / Q000737:chemistry*; D013237:Stereoisomerism; D014025:Titanium / Q000737:chemistry*
chemical_list: D009942:Organometallic Compounds; D011725:Pyridines; D013141:Spiro Compounds; D014025:Titanium