title: Synthesis of fused piperidinones through a radical-ionic cascade.
abstract: Azabicyclo[4.3.0]nonanes were assembled, from chiral allylsilanes possessing an oxime moiety, using a stereocontrolled formal [2 + 2 + 2] radical-ionic process. The cascade involves the addition of an alpha-iodoester to the less substituted end of the enoxime which is then followed by a 5-exo-trig cyclization onto the aldoxime function, producing an alkoxyaminyl radical species which finally lactamizes to afford the titled piperidinone. High levels of stereoinduction were observed, demonstrating the ability of a silicon group located at the allylic position to efficiently control the stereochemistry of the two newly created stereogenic centers. When the radical cascade was extended to ketoximes, the resulting sterically hindered alkoxyaminyl radical did not react further with the initiator Et3B to produce the expected nucleophilic amidoborane complex. In sharp contrast, this long-lived radical recombined with the initial alpha-stabilized ester radical to produce a cyclopentane incorporating two ester fragments.
authors: University Bordeaux 1, Institut des Sciences Moléculaires, UMR-CNRS 5255, 351, Cours de la Libération, F-33405 Talence Cedex, France.
authors: Edouard
authors: E
authors: Godineau
authors: Kurt
authors: K
authors: Schenk
authors: Yannick
authors: Y
authors: Landais
mesh_terms: D018360:Crystallography, X-Ray; D003500:Cyclization; D004952:Esters / Q000737:chemistry; D005609:Free Radicals / Q000138:chemical synthesis / Q000737:chemistry; D006574:Heterocyclic Compounds, 2-Ring / Q000138:chemical synthesis* / Q000737:chemistry; D006847:Hydrocarbons, Iodinated / Q000737:chemistry; D007477:Ions / Q000737:chemistry; D008958:Models, Molecular; D008968:Molecular Conformation; D010880:Piperidines / Q000138:chemical synthesis* / Q000737:chemistry; D012821:Silanes / Q000138:chemical synthesis* / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D004952:Esters; D005609:Free Radicals; D006574:Heterocyclic Compounds, 2-Ring; D006847:Hydrocarbons, Iodinated; D007477:Ions; D010880:Piperidines; D012821:Silanes