2-Cyano-Δ3-piperideines. 13. Synthesis and Reactivity of N-Protected Dehydrosecodine Equivalents

Article abstract of DOI:10.1021/jo00187a019

A direct synthesis of 1-(phenylsulfonyl)secodine (6) is accomplished by lithiation of 1-(phenylsulfonyl)-3-<2-(5-ethyl-1,2,3,6-tetrahydropyridyl)ethyl>indole (4), reaction with methyl pyruvate, and dehydration.The 2-cyano-Δ³-piperideine derivatives of both the carbinol precursor 9 and of 1-(phenylsulfonyl)dehydrosecodine 12 have been characterized.Various reaction conditions under which 1-(phenylsulfonyl)dehydrosecodine (14) could be generated have been examined but no products of either the Aspidosperma or Iboga structural type have been characterized.Instead, disproportionation of the dihydropyridine intermediate appears to be the dominant reaction.Reductive desulfonylation of the carbinol intermediate provides 16-hydroxy-16,17-dihydrosecodine (isosecodinol) (19) but under the same conditions 1-(phenylsulfonyl)secodine (6) generates 16,17-dihydrosecodine (18).