High diastereoselectivity in lewis acid mediated aldol condensations using thioester silyl ketene acetals.
โ Scribed by Cesare Gennari; Anna Bernardi; Silvia Cardani; Carlo Scolastico
- Publisher
- Elsevier Science
- Year
- 1985
- Tongue
- French
- Weight
- 248 KB
- Volume
- 26
- Category
- Article
- ISSN
- 0040-4039
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โฆ Synopsis
BF30Et2 mediated aldol condensations of thioester silyl ketene acetals are stereoconvergent, and exhibit high internal (anti) and relative (Cram) diastereoselectivity.
๐ SIMILAR VOLUMES
0-Silylated vinyl ketene aminal 2, obtained from lithiated unsaturated amide 1, undergoes a thermal [1,5] silicon migration to give y-silylated product 3b which participates in fluoride-and titanium tetrachloride-mediated aldol condensations to give adducts 5 in poor and excellent syn diastereoselec
Ketene silyl acetals such as (II) and (IV) are added in the presence of various Lewis acids (e.g. (C 6 F 5 ) 2 SnBr 2 ) to ketones with a extremely high level of chemoselectivity in competition with aldehydes or acetales (with exception of benzaldehyde). The generality of ketone preference is also e