Stereocontrol in N-directed hydroboration: synthesis of amino alcohols related to the piperidine alkaloids.
Treatment of 2-(2'-alkenyl)-piperidine boranes with iodine or triflic acid induces internal hydroboration with high regiocontrol, even with a terminal alkene (R = H). Good stereocontrol is possible for the N-benzyl substrates. Comparisons with acyclic model structures show that the source of regiocontrol with the terminal alkene is due to a steric effect of the axial piperidine C(3,5) hydrogens that destabilize the competing bridged bicyclic transition state.
Wang
Guoqiang
G
Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA.
Vedejs
Edwin
E
D000470:Alkaloids / Q000138:chemical synthesis* / Q000737:chemistry; D000475:Alkenes / Q000737:chemistry*; D000605:Amino Alcohols / Q000138:chemical synthesis* / Q000737:chemistry; D001880:Boranes / Q000737:chemistry*; D002384:Catalysis; D006572:Heterocyclic Compounds, Bridged-Ring / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D010880:Piperidines / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism
D000470:Alkaloids; D000475:Alkenes; D000605:Amino Alcohols; D001880:Boranes; D006572:Heterocyclic Compounds, Bridged-Ring; D010880:Piperidines