Silylation of bicyclic six-membered nitronates. Ring—chain tautomerism of intermediate N,N bis(oxy)iminium cations

Silylation of bicyclic six-membered nitronates was studied as a possible route to conjugated enoximes with a distant carbonyl group. Apart from the target enoximes, this reaction yielded nitro compounds. The ratio of these two types of products and the configurations of their stereogenic centers depend on the nature and configurations of the starting nitronates and the silylation conditions. The results obtained were interpreted in terms of ring—chain tautomerism of intermediate N,N-bis(oxy)iminium cations. Dedicated to Academician O. M. Nefedov on the occasion of his 75th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1983–1992, November, 2006.