Mechanism Michael addition reaction

Thomsen Click Organic Process to view an animation showing the mechanism of the Michael addition reaction. 

Main group organometallic polymerization catalysts, particularly of groups 1 and 2, generally operate via anionic mechanisms, but the similarities with truly coordinative initiators justify their inclusion here. Both anionic and coordinative polymerization mechanisms are believed to involve enolate active sites, (Scheme 6), with the propagation step akin to a 1,4-Michael addition reaction. 

Chan JW, Zhou H, Wei H, Hoyle C. (2008) Mechanism of the primary and secondary amine catalyzed thio-Michael addition reaction with (meth)acrylates. Abstracts of Papers, 235th ACS National Meeting, New Orleans, LA, United States, April 6-10,2008 168 pp. 

A proposed mechanism for the Michael addition reaction is shown in Scheme 10.7. Note that enamine, generated from the reaction of hydroxyacetone and aldolase antibody 38C2, reacts with the activated methylene group in 2-(phenyl)ethyl-2-(tri-fluoromethyl)acrylate. 

The mechanism of the Michael addition reaction using ester 3.3 and mesityl oxide is shown in Scheme 3.13. The enolate A derived from the malonic ester (3.3) attacks the (3-carbon... 

Murahashi and Naota studied the reaction mechanism of cyclopentadienyl ruthenium enolate complex-catalyzed aldol and Michael addition reactions [80-82]. This mechanistic study revealed that the cone angle of the tertiary phosphine ligands largely affects the stability of C- and N-bound complexes [80, 82], Thus, ligation of bulky phosphine ligand would favor the N -bound complexes [80]... 

A mechanism for the formation exo-5-morpholinobicyclo[2.2.1]heptan-2-one via a ho-moenolate ion intermediate in a Michael-type addition reaction has been proposed. Michael addition reactions involving secondary amines and a,)S-unsaturated carbonyl compounds have been reported, but this was the first example of such a reaction involving the ho-moenolate ion. ... 

Metal compounds possessing Lewis acid character are often used in the Michael addition reaction, and the methodology is reasonably applied to the asymmetric reaction in the presence of chiral ligands. The mechanism could involve either purely Lewis acidic activation of the Michael acceptor or generation of new orga-nometallic species by the transmetalation or C-H activation, although they were not clear in many cases. The system of Sn(OTf)2 and chiral (S)-diamine developed by Mukaiyama promoted the asymmetric addition of trimethylsilyl enethi-olate 68 to P-arylvinyl ketones (Scheme 13) [70, 71]. The diamine-coordinated tin enolate was considered to be involved, and slow addition of 68 was essential to inhibit the racemate formation process. 

Here catalysis involves the formation of a ruthenium vinylidene, an anti-Markovnikov addition of water (368), and cyclization of an acylmetal species onto the alkene. Although cyclization may occur via hydroacylation (Scheme 52, path A) (460-462) or the Michael addition reaction (Scheme 52, path B) (463,464), the requirement for an electron-withdrawing substiment on the alkene and the absence of aldehyde formation suggest path B to be the more likely mechanism (465,466). Trost discovered that the use of the cationic mthenium catalyst CpRu(MeCN)3+PFg is tolerant of 1,2-di-and trisubstimted alkenes and promotes cyclization of 1,6- and 1,7-enynes to five- and six-membered ring products (467). In a number of examples, the mthenium reaction is complementary to the Pd-catalyzed cyclization described above, selectively forming the 1,4-diene over the traditional 1,... 

Related to the copper-catalyzed Michael addition reaction, aUyl phosphates furnish substitution products via the anti Sn2 mechanism when treated with an appropriate (jrignard reagent in the presence of catalytic amount of CuCN and 1 equiv of TMSCl (eq 43). ... 

As in any solid-liquid reaction, when the solid is sparingly soluble, reaction occurs within the solid by diffusion of the liquid-phase reactant into it across the liquid film surrounding the solid. Thus two diffusion parameters are operative, the solid-liquid mass transfer coefficient sl and the effective diffusivity D. of the reactant in the solid. A reaction in the solid can occur by any of several mechanisms. The simpler and more common of these were briefly explained in Chapter 15. For reactions following the sharp interface model, ultrasound can enhance either or both these constants. Indeed, in a typical solid-liquid reaction such as the synthesis of dibenzyl sulfide from benzyl chloride and sodium sulfide ultrasound enhances SL by a factor of 2 and by a factor of 3.3 (Hagenson and Doraiswamy, 1998). Similar enhancement in was found for a Michael addition reaction (Ratoarinoro et al., 1995) and for another mass transfer-limited reaction (Worsley and Mills, 1996). 

Show the product and provide a mechanism for the following Michael addition reaction. 

Scheme 13.19 Proposed mechanism of nitro-Michael addition reactions catalysed by N-terminal primary amino dipeptides.

The salt-free propionates have found versatile technical applications in metal-working fluids, and because of their excellent alkali stability, in alkaline cleaning compounds. The acetates are more suitable for use in personal care or general cleaning applications. Some acetates have anti-microbial properties and are used as disinfectants. Alkylaminopropionates and alkylamin-odipropionates are synthesized by carboxyalkylation of fatty amines with methyl acrylate or acrylic acid, following the mechanism of the Michael (Addition) Reaction (Figure 15.21). 

Since the mechanism of chalcogenide-MBH reaction involved the Michael addition of chalcogenide to electron-deficient olefins and the intramolecular Michael addition reaction of a sulfide group to an enone moiety in an acidic medium is known, Kataoka et al. envisaged that the tandem Michael aldol... 

Early work by Tomioka and coworkers [39] described a two-component Michael/ aldol process to cyclopentenes. Furthermore, rhodium-assisted Michael/aldol processes to cyclopentanes and cyclohexanes have also been reported [40]. Later, a Michael addition reaction in combination with an adehyde a-alkylation reaction was reported for the highly stereoselective formation of y-nitroaldehydes 50 [41]. In this publication, a series of aliphatic aldehydes 49 (at Rj) and ( )-5-iodo-l-nitropent-1-ene 48 were reacted in the presence of the organocatalyst 1 and benzoic acid in dimethyl sulfoxide (DMSO) to afford the resulting cyclopentene ring system 50 (Scheme 7.9). The diastereo- and enantioselective process follows the proposed mechanism beginning with enamine activation of the aldehyde to 51 by the catalyst 1 (blocking the re face), and Michael addition of 48 occurs at its more accessible si face. The full enamine-enamine mechanism, illustrated in Scheme 7.9, provided... 

Stereospecific Michael addition reactions also may be catalyzed by hydrolytic enzymes (Scheme 2.205). When ot-trifluoromethyl propenoic acid was subjected to the action of various proteases, lipases and esterases in the presence of a nucleophile (NuH), such as water, amines, and thiols, chiral propanoic acids were obtained in moderate optical purity [1513]. The reaction mechanism probably involves the formation of an acyl enzyme intermediate (Sect. 2.1.1, Scheme 2.1). Being an activated derivative, the latter is more electrophilic than the free carboxylate and undergoes an asymmetric Michael addition by the nucleophile, directed by the chiral environment of the enzyme. In contrast to these observations made with crude hydrolase preparations, the rational design of a Michaelase from a lipase-scaffold gave disappointingly low stereoselectivities [1514-1517]. 

Figure 14.6 Michael addition mechanism between ethyl acetoacetate and methyl acrylate. Modified from Mather, B.D., Viswanathan, K., Miller, K.M., Long, T.E., 2006. Michael addition reactions in macromolecular design for emerging technologies. Prog. Polym. Sci. 31, 487—531 with permission from Elsevier.

From the point of the reaction mechanism, this reaction consisted of two parts a Michael addition reaction and an intramolecular Heck type coupling reaction. 

Although, at this point, the mechanism of this reaction is not clear, the authors proposed a reasonable mechanism as shown in Scheme 11.6. The formation of cyclohexa-1, 3-dienes was explained as follows firsL the Knoevenagel condensation of aryl aldehyde 53 with malononitrile 54 gives malononitrile 58. Next, the Michael addition reaction of 55 with malononitrile 58 affords intermediate 59, followed by the intramolecular cyclization to render intermediate 60. 

This chapt er covered many C—C bond-forming reactions, including aldol reactions, Claisen condensations, and Michael addition reactions. Two or more of these reactions are often performed sequentially, providing a great deal of versatility and complexity in the type of stmctures that can be prepared. Propose a plausible mechanism for each of the following transformations. 

B. Karimi and H. Behzadnia pubhshed the preparation of coumarins using PMSCl (7 mol%) with 2DP6mm hexagonal structure under solvent-free conditions at 130°C. Proposed mechanism for this reaction is demonstrated in (Scheme 22). The transesterification of the phenol and EAA in the presence of PMSCl as a Lewis acid catalyst generates species 33. Alternatively, Michael addition reaction creates a new ring to afford species 34. Rearomatization leads to the formation of the coumarin skeleton 35. Final-phase PMSCl is regenerated by dehydration (11CCAOAC1432). 

A wide range of chemistries have been evaluated to provide adhesives that have properties that are an improvement over epoxies and phenolics. The primary property that has been sought is an improvement in the high-temperature resistance of these adhesives. Bis-maleimide is one of the chemistries that have been evaluated for this purpose. The stmcture of a his-malermide is shown in Figure 9. Bis-maleimides can be cured into a stractural adhesive by one of three reaction mechanisms. The first one shown is the reaction of a bis-maleimide with an amine via a Michael addition reaction. The second one shown is the Diels-AIder reaction of a diene and the bis-maleimide. A third mechanism (not shown) is radical addition. 

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