Polyfunctional β‐Dicarbonyl Compounds by Michael Addition Reactions of Ester Enolates to α‐Benzylidene and α‐Alkylidene‐β‐dicarbonyl Compounds

Abstract

The scope and stereoselectivity of the Michael addition of ester enolates to α-benzylidene and α-alkylidene β-dicarbonyl compounds was studied. Most substrates reacted in good to excellent yields. Michael acceptors bearing carboxylic functionalities reacted directly in the β-position, whereas aldol and Michael addition competed with unsaturated ketones. The diastereoselectivity of the process is dependent on the substitution pattern of the Michael acceptor and the [a] 3461 Scheme 4. Michael addition reactions of 4-pentenoates 1a-e to ylidenemalonates 2A-C.Table 2. Results of the Michael addition reactions of 1a-e to malonate acceptors 2A-C. Entry Enolate 2 Solvent T [°C] 3 [%] anti/syn [a]www.eurjoc.org

Highly Functionalized and Potent Antiviral Cyclopentane Derivatives Formed by a Tandem Process Consisting of Organometallic, Transition‐Metal‐Catalyzed, and Radical Reaction Steps

“…The results indicate that the additions of enolates 4 to malonate or dibenzoylmethane derivatives 6 (R 4 = OEt or Ph) proceed via chelated transition states anti-and syn-16, [12,21] in which the lithium atom of the enolates 4 coordinates the Z-oriented carbonyl group. [21] The orientation in transition state anti-16 is more favorable than that in syn-16, however, from the moderate diastereoselectivity obtained, it can be concluded that the energetic difference between them is moderate in all cases. The resulting enolates anti-and syn-17 are stabilized and thus unreactive to further organometallic reaction steps.…”

Highly Functionalized Cyclopentane Derivatives by Tandem Michael Addition/Radical Cyclization/Oxygenation Reactions

“…It was known that all of the Michael acceptors 2 E–I underwent the Michael addition with low diastereoselectivity 14. It was nonetheless of interest to learn the factors influencing the radical cyclization selectivity.…”

“…Based on optimized Michael addition conditions, [14] the tandem reactions were initiated by selectiveg eneration of the (E)-or (Z)-enolates by using esters 1 and lithium diisopropylamide (LDA), followed by addition of Michael acceptors 2.A fter completion of this step, TEMPO (5)a nd ferrocenium hexafluorophosphate (4)w ere introduced to mediate the SET oxidation, cyclization,a nd oxygenation (see Ta bles [1][2][3][4]. It proved to be optimal to add 12.5 mol %o f5first andathoroughly homogenizedm ixture of 4 and 5 subsequently in small portions.…”

“…The diastereoselectivity of the overall tandem sequence is strongly dependent on the diastereoselectivity of the Michael addition step and the substitution pattern of the alkene cyclization acceptor. ( Z )‐Enolates of esters and ketones give Michael adduct enolates anti ‐ 3 − , often with good diastereoselectivity 14…”

Polyfunctional β‐Dicarbonyl Compounds by Michael Addition Reactions of Ester Enolates to α‐Benzylidene and α‐Alkylidene‐β‐dicarbonyl Compounds

“…In the original article, 1 some experimental details were inadvertently omitted, and the following changes must be introduced:…”