Reactions of Oxocarbenium Cations

An early study of the allylation reactions of oxocarbenium systems has been described by Danishefsky for synthesis efforts directed towards indanomycin. The reactions of ( )-and (Z)-2-butenylsilanes silanes are the focus for this report. However, the study also examined reactions of the (E,Z)-mixture of 2-butenyl-tri-n-butylstannanes with tri-o-acetyl-o-galactal 132 at -30 °C, in the presence of BF3 OEt2 

Lewis acids are commonly used to initiate solvolysis, as in the production of iV-acyliminium species 165, and diastereoselectivity is observed based on the minimization of steric factors in 166. In the N-Boc derivative 165, the vicinal methyl substituent of the half-chair conformer is placed axially to avoid in-plane strain, suggesting the development of 1,3-diaxial interactions in 166 leading to 167.51 

---