Monitoring Reaction Intermediates in the FeCl₃-Catalyzed Michael Reaction by Nuclear Inelastic Scattering

Abstract

We present a study of the metal-centered vibrations in the first step of the Fe(III)-catalyzed Michael reaction. Nuclear inelastic scattering of synchrotron radiation was carried out on a shock-frozen solution of FeCl3.6H2O in 2-oxocyclopentane ethylcarboxylate (CPEH), as well as on the solid reference compounds FeCl3.6H2O, [N(CH3)4][FeCl 4], and Fe(acac) 3. In addition to the vibrations of the FeCl4(-) anion at 133 and 383 cm(-1), a multitude of modes associated with the complex Fe(CPE)2(H2O)2 could be identified. Normal-mode analysis on different isomers of the simplified model complex Fe(acac)2(H2O)2 as well as that of the full complex carrying two entire CPE ligands was carried out using density functional calculations. Comparison with experiment suggests that the facial bis(diketonato) isomer probably dominates in the reaction mixture. Thus, we have identified for the first time the isomeric structure of an iron-based intermediate of a homogeneous catalytic reaction using nuclear inelastic scattering.

Michael Acceptors as Anti-Cancer Compounds: Coincidence or Causality?

“…The Michael reaction, in which an enolate is added to an activated alkene typically represented by an α,β-unsaturated carbonyl compound, is considered one of the most efficient methods for forming C-C bonds [ 15 , 16 ]. Originally discovered by Arthur Michael in the late 1880s, this reaction has been extensively researched and led to the development of numerous reaction variants [ 17 , 18 , 19 , 20 , 21 , 22 , 23 ]. Among these, hetero-Michael additions such as oxa- [ 24 , 25 , 26 , 27 ], aza- [ 28 , 29 ], thia- [ 30 , 31 , 32 , 33 , 34 ] and phospha-Michael reactions [ 35 ] represent extensions of this concept to heterocentric anions ( Figure 1 ).…”

Advances of Iron(III) Chloride-Catalyzed Organic Reactions

“…Michael 加成是构筑碳-碳键的重要手段之一, Brønsted 碱、酸和金属化合物均可用于催化该类反应, 在诸多催化剂中, 铁催化剂具有很大的优势. Asthalter 等 [28] 研究发现, FeCl 3 在温和的条件下可有效催化一系 列的直链和环状二羰基化合物和不同底物(如丁烯酮)的 反应(Eq. 5).…”

B(C6F5)3-Catalyzed Michael Reactions: Aromatic C–H as Nucleophiles

“…The Michael reaction, namely the addition of an enolate to an activated alkene such as an α,β-unsaturated carbonyl compound, is one of the most efficient and effective routes to the formation of C–C bonds (Scheme , eq 1) . Since its discovery by Arthur Michael in the late 1880s, the Michael reaction has been extensively studied, and numerous variants of this reaction have been developed . The hetero-Michael addition including the oxa -, aza -, thia -, and phospha -Michael reactions is the extension of this concept to heterocentered anions (Scheme , eq 2).…”