Trimethylsilyl trifluoromethanesulfonate-promoted cycloaddition of nitrones with silyl enol ethers: synthesis and reactivity of 5-siloxyisoxazolidines

In the presence of trimethylsilyl trifluoromethanesulfonate (TMSOTf), the reaction of nitrones with silyl enol ethers affords 5-siloxyisoxazolidines under mild conditions, in good to excellent yields. 5-Siloxyisoxazolidines can undergo chemoselective reductions to Manoich bases or N-hydroxy-1,3-amino alcohols, and, in the presence of TMSOTf, react with silylated carbon nucleophiles at the acetalic C-5 carbon to give, for example, 5-allyl- and 5-cyano-isoxazolidines

Regioselective addition of 1-trimethylsilyloxy-1-methoxy-1,3-dienes to aldonitrones catalysed by trimethylsilyl triflate

1-Trimethylsilyloxy-1-methoxy-1,3-dienes (3a-d) regioselectively add to aldonitrones at -20°C in dichloromethane in the presence of 10-20 % of trimethylsilyl triflate to give γ-adducts in high yields; on the other hand, 1-trimethylsilyloxy-1-methoxy-1,3-hexadiene (3e) displayes a reversed regiochemical preference affording the α-adduct as the major product