Diastereoselectivity in the directed aldol reactions of 1-fluoro-3,3-dimethyl-butanone enolates and enol silyl ethers.

Stereochemical Control in Organic Synthesis Using Silicon-Containing Compounds

“…Many ketone-derived silyl enol ethers are similar to the ester-derived silyl enol ethers, with occasional exceptions such as 532 , which gives high diastereoselectivity in favor of the anti aldol 533 (Scheme ). Even a small change in the structure of an exceptional case like this can change the selectivity significantly: replacing the methyl group in the silyl enol ether 532 by a fluorine atom reduces the selectivity in favor of the anti isomer to 60:40 . For ketone-derived silyl enol ethers, there is a trend for those reactions catalyzed by boron trifluoride to favor the syn arrangement, and for those reactions catalyzed by titanium tetrachloride to favor the anti arrangement.…”

Fluorinated Carbonyl and Olefinic Compounds: Basic Character and Asymmetric Catalytic Reactions

“…Fluorine-containing carbonyl compounds can also be employed as fluorine-substituted building blocks. However, metal enolates of carbonyl compounds as nucleophiles, which are of central importance in the synthesis of non-fluorinated compounds, have been severely limited on α-F metal enolates to be stabilized by M−F chelate structures . On the other hand, α-CF 3 metal enolates have been generally recognized to be very unstable and hence difficult to prepare because of the rapid β-M−F elimination …”

Regio- and stereoselective synthesis of vicinal fluorohydrins

“…However, the fluorinated ester or amide enolates exhibited poor diastereoselectivity [32][33][34][35][36]. The diastereoselectivity in favor of the syn-products was improved slightly using more bulky a-fluoroacetates [37] but significantly in the case of 1-fluoro-3,3-dimethylbutanone as the C-H active component and aliphatic aldehydes [38]. Also the aldol type reaction of an enolate of a-fluoro acetone with formaldehyde provides the corresponding fluorohydrin (Scheme 4) [39].…”