Michael fluoride catalyzed

Formally similar intramolecular denitrocyclization reaction takes place during a fluoride-catalyzed Michael addition of nitrotoluenes 159 to un saturated... 

In 1978, Wynberg and coworkers reported the first example of a chiral quaternary ammonium fluoride-catalyzed Michael addition of nitromethane to chalcone (Scheme 9.1) [3]. The reaction was performed in toluene at 20 °C with 10mol% of chiral ammonium salt 1 or 3a and excess potassium fluoride (KF, 15 equiv.), yielding the y-nitro ketone with 10-23% enantiomeric excess (ee). The requisite chiral... 

Asymmetric Michael Addition of Nitromethane to Enone. N-Methylephedrinium fluoride catalyzes the Michael addition of nitromethane to chalcone to afford the adduct with 23% ee in 50% yield (eq 27). ... 

Michael additions of nitro olefins. Potassium fluoride catalyzes the Michael addition of 1,3-diketones and simple nitro olefins (equation I). Products of further transformation of the initial adduct are formed in some cases (equation... 

The tosylate 191 was synthesized from the malononitrile 194 obtained in modest yield by potassium fluoride catalyzed Michael addition of malononitrile to 3,6, trimethyl-2-cyclohexenone. A series of unexceptional steps led from 194 to 191 obtained in overall yield of 26%. 

Recently, an oxidative dearomatization of substituted phenols followed by a desymmetrizing asymmetric intramolecular Michael addition catalyzed by the pro-linol derivative 27 has been described towards the synthesis of highly functionalized polycyclic molecules with excellent enantioselectivities [40]. As shown in Scheme 2.15, the reaction starts with an oxidation of the phenol moiety to the corresponding mera-cyclohexadienones employing PhlCOAc), mild oxidant that does not react with the aldehyde nor with the catalyst. In the presence of different nucleophiles such as, methanol, cyanide, or fluoride, intermediates 26 are formed, which suffer intramolecular Michael addition of the aldehyde moiety to afford the desired chiral products 28 with excellent diastereo- and enantioselectivities. 

Polymer-supported podands appear to be more commonly used in solid-liquid systems. A variety of chemical transformations including nucleophilic substitutions at saturated carbon atoms [214,215], esterifications [214], sodium bo-rohydride reduction [214], fluoride-catalyzed Michael addition [214], phenacyl ester synthesis, Darzen s reaction, Wittig alkenylation, and dichlorocarbene reactions can be carried out under these conditions [214],... 

Naked fluoride-catalyzed Michael additions. I. Belsky, J. C. S. Chem. Commun., 237 (1977)... 

Matsumoto, K. (1981) High pressure Michael addition catalyzed by fluoride ions, Angew. Chem. Int. Ed. Engl, 20,770-1. 

The anions, generated in situ by desilylation of silylacetylenes, allylsilanes, propargylsilanes, a-silyloxetanones, bis(trimethylsilylmethyl) sulfides, and other silane derivatives,can undergo nucleophilic addition to ketones and aldehydes (eq 11). Al-(C,C-bis(trimethylsilyl)methyl) amido derivatives can add to aldehydes followed by Peterson alkenation to form acyl enamines. Treatment of 2-trimethylsilyl-l,3-dithianes can generate dithianyl anions, which are capable of carbocyclization via direct addition to carbonyl or Michael addition (eq 12). The fluoride-catalyzed Michael additions are more general than Lewis acid-catalyzed reactions and proceed well even for those compounds with enolizable protons and/or severe steric hindrance (eq 13). ... 

The thiazolium-catalyzed addition of an aldehyde-derived acyl anion with a Michael acceptor (Stetter reaction) is a well-known synthetic tool leading to the synthesis of highly funtionalized products. Recent developments in this area include the direct nucleophilic addition of acyl anions to nitroalkenes using silyl-protected thiazolium carbinols <06JA4932>. In the presence of a fluoride anion, carbinol 186 is not cleaved to an aldehyde... 

Some Michael additions of unsaturated reagents to imidazoles involve the neutral species of the heterocycles, but others may be reactions of the anion. Fluoride ion catalyzed addition of 2-methyl-4-nitroimidazole (113) to a suitable Michael acceptor gives almost quantitative yields of the 1-substituted 4-nitroisomers (114) (90JOC3702,91JCR(S)35o). 

Intramolecular conjugate allylation (12, 25).2 Fluoride ion catalyzes intramolecular Michael additions of allyltrimethylsilane to a,p-enones as well as a,p-unsaturated esters, nitriles, and amides Lewis acid catalysis is not effective. The method is particularly suited to cyclopentane annelations.2... 

Nef transformation,3 A versatile route to 1,4-diketones involves Michael addition of a nitroalkane to an a,/J-enone, which can be effected in 80% yield when catalyzed by fluoride ion (9, 446-447). The resulting y-nitro ketone is oxidized efficiently by a stoichiometric amount of KMn04 impregnated on silica gel to a 1,4-... 

Michael addition. Fluoride ion can catalyze Michael additions.4 In reactions that are slow owing to steric hindrance, or where elimination or fragmentation competes, use of high pressure5 may prove expeditious. 

The first pentalene to be synthesized free of fused rings was the hexaphenyl derivative (752).232) The approach involved fluoride ion-catalyzed Michael addition-Knoevenagel dehydration of 1,2,3-triphenylcyclopentadiene with 1,2,3-triphenyl-propenone and subsequent oxidation with N-bromosuccinimide in CCI4. 

Conjugate addition to acyclic Michael acceptors. Sakurai and Hosomi (9, 445-446) reported one example of the fluoride ion-catalyzed reaction of allyltrimethylsilane with an acyclic enone. In that case (reaction with C6H5CH=CHCOCH,). 1.2- and 1,4-adducts are obtained in the ratio 2 1.1,4-Addition is enhanced by use of DMF and HMPT as solvent and by increase in the size of the group adjacent to the carbonyl group. 1,4-Addition is the main or predominant reaction with a,3-unsaturated esters or nitriles. In this case, it is superior to or competitive with allylation with lithium diallylcuprate. Yields in 1,4-additions to a,p-enones can compare favorably with those obtained with reactions catalyzed by TiC. ... 

Intramolecular conjugate additions/ This fluoride ion-catalyzed Michael addition is particularly useful for cyclization of suitably substituted allyltrimethylsilanes with a Michael acceptor. In the examples cited, BE, is not useful, because its use results in desilylation or isomerization. 

Asymmetric Michael Reactions. Asymmetric induction has been observed in Michael-type addition reactions that are catalyzed by chiral amines. The Ai-benzyl fluoride salt of quinine has been particularly successful since the fluoride ion serves as a base and the aminium ion as a source of chirality. Drastic improvements in optical purity (1-23%) have resulted by changing from quinine to the N-benzyl fluoride salt (eq 11). ... 

C ampelo, JM Climeiu. MS Marinas, JM. Michael addition of niiromcihanc to 3-buten-2-onc catalyzed by pinassium fluoride supported on alumina, zinc oxide, tin dioxide, scpiolilc, aluminum phosphate. AlP04-AI Oi and AIP04-ZnO. Reaction Kinetics and Catalysis Letters. 1992 47, 7-11. 

KF-catalyzed Michael reactions. Fluoride ion solubilized by 18-crown-6 is an efficient catalyst for Michael reactions in aprotic solvents (CeKa, CH2CI2, t H ,CN). ... 

Ohtani et al. used polystyrene-supported ammonium fluoride as a phase transfer catalyst (triphase catalysis) for several base-catalyzed reactions, such as cyanoethylation, Knoevenage reaction, Claisen condensation and Michael addition. The catalytic activity of the polystyrene-supported ammonium fluid was comparable to that of tetrabutylammonium fluoride (TBAF). The ionic loading and the ammonium structure of the fluoride polymers hardly affected the catalytic efficiency. The reaction was fast in a non-polar solvent (e.g., octane or toluene) from which the rate-determining step of the base-catalyzed reaction is very similar to that of the nucleophilic substitution reactions. 

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