New Types of Siloxy-substituted 1,3-Diene

Rawal et al. have reported that under mild reaction conditions l-amino-3-siloxy-1,3-butadiene 105 a adds smoothly to a variety of dienophiles, for example electron-deficient alkynes and alkenes [290], aldehydes, aldimines [291], and ketones 

2 Achiral Brensted and Lewis Acid-promoted Reactions 

In the nineteen-eighties stoichiometric amounts of conventional Lewis acids such as TiCl4, AICI3, SnCU, BFs-Olt,., Mgl r, and ZnCU were frequently used for HDA reactions of siloxy-substituted dienes with heterodienophiles [286, 287]. Danishefsky et al., however, found that a lanthanide shift reagent such as Eu(fod)3 can promote the cycloaddition catalytically [294]. Several Bronsted and Lewis acids have recently been shown to have high catalytic activity in the DA reaction of siloxy-substituted dienes in non-aqueous or aqueous media, and elaboration of Lewis acids has achieved unique chemo- and regioselectivity. 

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