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Publication 133  

  1. Stable and reactive conformations of N-enoyl-bornane-10.2-sultams in the absence of lewis acids : asymmetric 1.4-hydride additions
    Oppolzer, W.; Poli, G.; Starkemann, C.; Bernardinelli, G.
    Tetrahedron Lett. 1988, 29, 3559-3562

Ground-state conformations of non-chelated N-enoylsultams were determined by X-ray-(1, 3) and 1H-NMR-LIS evidence. Conjugate additions of lithium tri-s-butylborohydride to 1 and 3 followed by O-acylation of the non-isolated “enolates” furnished stereoselectively either (Z) or (E)- O-acyl-N,O-ketene acetals (1 → 2, 3, → 4) depending on the s-cis-/s-trans-conformation of the N-enoylsultams. X-ray diffraction analyses of sultam derivatives 1, 2, 3 and 4 show a pyramidal nitrogen atom. This information provides an insight into the π-face discriminations observed on addition reactions to non-coordinated enoylsultams (e.g. I → II, I → III).

DOI : 10.1016/0040-4039(88)85292-4