Synthesis of 1,3-Diketones and β-Keto Thioesters via Soft Enolization

Abstract

Ketones and thioesters undergo soft enolization and acylation using crude acid chlorides on treatment with MgBr 2 •OEt 2 and i-Pr 2 NEt to give 1,3-diketones and β-keto thioesters, respectively. The use of crude acid chlorides adds efficiency and cost reduction by avoiding the need to purify and/or purchase them. The process is conducted in a direct fashion that does not require prior enolate formation, further enhancing its efficiency and making it very easy to carry out. The method is suitable for large scale applications.

Retrosynthetic Analysis of α-Alkenyl-β-Diketones: Regio- and Stereoselective Two-Step Synthesis of Highly Arylated Representatives from Acetylenes, Ketones, and Acyl Chlorides

“…Next, potassium dienolate, formed as a primary adduct of C–H functionalization (Scheme ), was subjected to the Claisen condensation with ethyl acetate in a one-pot manner. Because of the inefficiency of this protocol under a variety of reaction conditions, we began looking for a better approach for the introduction of the acyl moiety and finally realized that in terms of mild reaction conditions, acylating agent availability, and functional group tolerance, the best route would be a soft enolization of β,γ-unsaturated ketones 1 followed by acylation with acyl chlorides 2 .…”

A π-extended β-diketiminate ligand via a templated Scholl approach

“…TBP AcAc was prepared in 75% yield via soft-enolization of 4- t Bu-desoxybenzoin ( t Bu DOB) 16 with Hünig's base/MgBr 2 ·Et 2 O and reaction with 4- t Bu-benzoyl chloride. 17 Inspired by a reported procedure for the synthesis of bulky BDI ligands, 18 double imine condensation between TBP AcAc and 4-mesityl aniline was achieved using TiCl 4 as a dehydration agent, giving pre-ligand TBP BDI in 87% yield. The number of signals in both 1 H and 13 C NMR spectra of TBP BDI suggests a cis–trans conformation of the diimine motif in the solution state, as opposed to a C 2v symmetric cis–cis or trans–trans conformation ( Scheme 1 ).…”