Michael addition chemistry

The most extensive mechanistic studies of quinone Michael addition chemistry involve the arylsufinic acids, which yield reduced product (50,51). The sulfones produced in such reactions have been examined electrochemicaHy (48) and kineticaHy (52). The influence of substitutents in the quinone has... 

Quinone dyes, 9 503 Quinone ketals, anodic oxidation of hydroquinone ethers to, 21 264 Quinone methides, 2 209-211 Quinone Michael addition chemistry, 21 248-249, 250, 252 Quinone monoacetals, 21 251 Quinone monoimine (QMI), 19 246 Quinone oximes, formation of,... 

In an equally distinguished example, Langer et al. demonstrated the synthesis of a 140-membered library of degradable polymers from diacrylate and amine monomers (compare Fig. 6) that were polymerized via aza-Michael addition chemistry [80],... 

Krishna PR, Sreeshailam A, Srinivas R (2009) Recent Advances and Applications in Asymmetric Pkza-Michael Addition Chemistry. Tetrahedron 65 9657... 

After publishing the facile synthesis of tran -cyclooctene derivatives from the readily accessible cfr-cyclooctene (Royzen et al., 2008), Fox and colleagues extended this work to develop a fast bioconjugation strategy based upon the IVED-DA cycloadditions (Blackman et al., 2008). Maleimide functional frans-cyclooctene was coupled to thioredoxin (after reduction to produce the solvent exposed cysteine) via standard Michael addition chemistry. The now trans-cyclooctene functional thioredoxin (Trx-ene) could then be further modified extremely efficientiy with an electron-deficient tetrazine (3,6-di-(2-pyidyl)-i-tetrazine) shown in the left side of Figure 2.15. The overall strategy is depicted in Scheme 2.5. 

Several years after these first attempts to make arborescent structures, Tomalia revisited the chemistry used by Vogtle, giving particular attention to both the purification of the products obtained and the selectivity of each reaction carried out. He benefited from the efforts at Dow Laboratories to improve the Michael addition chemistry, which he directed toward the preparation of... 

Nucleophilic Substitution Reactions. Many of the transformations reali2ed through Michael additions to quiaones can also be achieved usiag nucleophilic substitution chemistry. In some iastances the stereoselectivity can be markedly improved ia this fashion (100), eg, ia the reaction of ben2enethiol with esters (R = CH C O) and ethers (R = 3) 1,4-naphthoquiaones. 2-Bromo-5-acetyloxy-l,4-naphthoquiQone [77189-69-6J, R = Br, yields 75% of 2-thiophenyl-5-acetyloxy-l,4-naphthoquinone [71700-93-1], R = SC H. 3-Bromo-5-methoxy-1,4-naphthoquinone [69833-10-9], R = Br, yields 82% of 3-thiophenyl-5-methoxy-l,4-naphthoquinone [112740-62-2] R = SC H. ... 

A number of BMI resias based on this chemistry became commercially available through Rhc ne Poulenc for appHcation ia priated circuit boards and mol ding compounds and Rhc ne Poulenc recognized the potential of bismaleimides as building blocks for temperature-resistant thermoset systems. The basic chemistry, however, was not new, because the Michael addition reaction had been employed by Du Pont to obtain elastomeric reaction products from bismaleimides and Hquid polymeric organic diamines (15). 

While the Michael-addition of a,P-unsaturated carbonyl and related compounds constitutes one of the most important fundamental synthetic reactions in organic chemistry, the y-addition developed by Trost and Li of nucleophiles to 2-alkynoates catalyzed by a phosphine provides... 

The final example of a domino process under high pressure, to be discussed in this chapter, is a combination of a Horner-Wittig-Emmons (HWE) reaction with a Michael addition developed by Reiser and coworkers [5]. Hence, reaction of a mixture of an aldehyde such as 10-18, a phosphonate 10-19 and a nucleophile 10-20 in the presence of triethylamine at 8 kbar led to 10-21. By this method, (3-amino esters, 3-thio esters and 3-thio nitriles can be prepared in high yield (Scheme 10.4). Many of these transformations do not occur under standard conditions, thereby underlining the importance of high pressure in organic chemistry. 

Michael, A. J. Prakt. Chem. 1887, 35, 349. Arthur Michael (1853-1942) was horn in Buffalo, New York. He studied under Robert Bunsen, August Hofmann, Adolphe Wurtz, and Dimitri Mendeleev, but never bothered to take a degree. Back to the United States, Michael became a Professor of Chemistry at Tufts University, where he married one of his most brilliant students, Helen Abbott, one of the few women organic chemists in this period. Since he failed miserably as an administrator, Michael and his wife set up their own private laboratory at Newton Center, Massachusetts, where the Michael addition was discovered. 

Shi, B. Greaney, M. F. Reversible Michael addition of thiols as a new tool for dynamic combinatorial chemistry. Chem. Commun. 2005, 886-888. 

Keywords 1,3-Dicarbonyls, Biginelh reaction, Hantzsch reaction, Heterocyclic chemistry, Knoevenagel condensation, Mannich reaction, Michael addition, Multi-component reactions... 

Pyridine and its partially or totally unsaturated derivatives such as tetrahydropy-ridines, DHPs, and piperidines are ubiquitous cores found in numerous natural product skeletons and in synthetic compounds of primary interest for synthetic chemistry, agrochemistry, or pharmacology. Among the various methodologies available for the synthesis of these compounds, multicomponent approaches have attracted much attention in the last few years. Most of these sequences are initiated by a Michael addition. 

Another important reaction in synthetic chemistry leading to C-C bond formation is the Michael addition. The reaction typically involves a conjugate or nucleophilic 1,4-addition of carbanions to a,/l-unsaturated aldehydes, ketones, esters, nitriles, or sulfones 157) (Scheme 21). A base is used to form the carbanion by abstracting a proton from an activated methylene precursor (donor), which attacks the alkene (acceptor). Strong bases are usually used in this reaction, leading to the formation of byproducts arising from side reactions such as condensations, dimerizations, or rearrangements. 

Electron-poor alkenes are suitable starting points for Michael additions. For example, the arylidene malononitrile 363 adds quantitatively to solid dimedone (255) upon milling at 80 °C followed by heating of the yellow powder to 100 °C. The initial Michael adduct 364 is not isolated, as it cyclizes in the solid state to give the pyrone 365 with 100% yield [107] (Scheme 58). The potentials for waste-free solid-state chemistry are manifold indeed and deserve further exploration. 

Chemistry Basic Elements Michael Addition Reaction... 

The sequence that follows illustrates how a conjugate aldol addition (Michael addition) followed by a simple aldol condensation may be used to build one ring onto another. This procedure is known as the Robinson annulation (ring forming) reaction (after the English chemist Sir Robert Robinson, who won the Nobel Prize in Chemistry in 1947 for his research on naturally occurring compounds). 

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