7015-01-2Relevant articles and documents
Silicon-Directed Nazarov Reactions II. Preparation and Cyclization of β-Silyl-substituted Divinyl Ketones
Jones, Todd K.,Denmark, Scott E.
, p. 2377 - 2396 (2007/10/02)
Two general methods for the preparation of β-silyl-substituted divinyl ketones have been developed starting from either α,β-unsaturated aldehydes or simple ketones.Anhydrous FeCl3 induces the cyclization to cyclopentenones under mild conditions and in good yields with predictable and complete control over the position of the double bond in the five-membered ring.The observed effects of substituents on rate can be explained by a rate-determining cationic electrocyclization.Silyl substitution has been shown to retard the reaction.
3-Triethylsilyloxypentadienyllithium, a Versatile 1,3-Diene- or Vinyl ketone-Building Block
Oppolzer, Wolfgang,Snowden, Roger L.,Simmons, Dana P.
, p. 2002 - 2021 (2007/10/02)
Deprotonation of the 3-trialkylsilyloxy-1,4-diene 3a and subsequent electrophilic substitution of the non-isolated 3-trialkylsilyloxypentadienyllithium 4 gives the α- and γ-products 8 and/or 6 in good yields.Whereas alkylation of 4 proceeds with variable regioselectivity (Table 1) aldehydes and ketones attack preferentially the γ-position of 4 (Table 2).The desired γ-products 6 may be directly subjected to inter- and intramolecular -additions as demonstrated by the reactions 5a(=6d)-->7 and 6h-->19 (schemes 4 and 12).Alternatively, smooth fluoride-promoted silylether-cleavage 6-->11 (Scheme 8) provides a convenient approach to substituted vinyl ketones such as to the natural product 11f (Table 3).The stereoselective conversion 6k-->23 (Scheme 13) implies an endo-selective intramolecular Diels-Alder addition (26-->23) and exemplifies the use of 4 as an equivalent of the hypothetical anion IV.Furthermore, some electrophilic substitutions of the hexadienyllithium 15 have been studied (Scheme 10).
