Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Intramolecular, addition Friedel-Crafts alkylation

Other methods for the regioselective SN2-opening of vinyloxiranes include intramolecular enolate addition for formation of cyclohexane systems [135, 136] and Friedel-Crafts alkylations [49, 137, 138]. [Pg.338]

The possible importance of side reactions such as Friedel Craft alkylation, inter or intramolecular Diels Alder cyclization or re-addition of HC1 in this context have also been emphasised (43). [Pg.236]

SnCU-promoted intramolecular additions of allylsilanes to /3-lactones proceed smoothly to give differently substituted cyclopentanes (Eq. 61) [94], When the a-ben-zyloxy-/3-lactone is subjected to standard cyclization conditions, the expected cyclopentane product is only obtained as a minor product the major product, isochroman, is derived from a Friedel-Crafts alkylation (Eq. 62). [Pg.420]

Intramolecular Friedel-Crafts alkylation forming a seven-membered ring by a formal Michael addition at the terminus of a 3-ethynyl-2-benzyl-2-cyclohexenone unit is made sterically possible by the presence of EtSH. ... [Pg.81]

Synthesis by Other Cyclizations. The epimeric amines (49) have been made by means of a novel S 2 reaction of the corresponding 2-bromo-6-amino-cyclohexanone derivative. Double Michael addition of (+)-a-methylbenzyl-amine to cyclo-octa-2,7-dienone derivatives forms the basis of a synthesis of the enantiomeric forms of adaline (50). Intramolecular Friedel-Crafts alkylation has been used in the synthesis of derivatives of the 2,6-methanobenz-azepine, 2,6-methano-3-benzazocine, 2,6-methano-3-benzazonine, and... [Pg.449]

The Friedel-Crafts alkylation is one of the oldest synthetic methodologies known. The catalytic asymmetric version of the reaction [311] enables the preparation of important chiral building blocks. Electron-rich aromatic and heteroaromatic compounds have been productively used in organocatalyzed enantioselective inter- and intramolecular Friedel-Craft-[312] type conjugate additions over different Michael acceptors such as, a,p-unsaturated aldehydes, a,P-unsaturated ketones, nitroole-fins, and a,p-unsaturated acyl phosphonates. [Pg.149]

Friedel-Crafts Reactions. Aluminum trifluoromethanesulfonate has been used for the Friedel-Crafts alkylation reaction of toluene with isopropyl and tert-butyl chlorides (eq 1), and for the acylation of benzene and toluene with acetyl and benzoyl chlorides in low to moderate yields. Intramolecular Friedel-Crafts acylation of an aromatic compound with Meldrum s acid has also been reported using catalytic amounts of Al(OTf)3. Acylation of 2-methoxynaphthalene with acetic anhydride has been reported using Al(OTf)3 and lithium perchlorate as an additive to afford the corresponding 6-acetylated adduct in 83% yield. Effective acylation of arenes with carboxylic acids has also been disclosed using polystyrene-supported Al(OTf)3. ... [Pg.25]

Several other asymmetric inter- as well intramolecular Friedel-Crafts alkylation with a,(3-unsaturated aldehydes have been described but without any configurative assignment [91]. Asymmetric carba-Michael additions of aldehydes to enones catalyzed by a chiral imidazolidin-4-one were reported by GeUman et al. [8] (Scheme 4.23). [Pg.83]

In 2009, Cai et al. reported a cascade olefin cross-metathesis/intramolecular Friedel-Crafts alkylation for the construction of polycyclic indoles 133 (Scheme 5.89) [90], A Ru complex (134)/chiral Brpnsted acid [(S)-135] binary system was used in this relay catalysis. Recently, the same group reported an enantioselective intramolecular aza-Michael addition of indoles using a similar binary catalyst system (Scheme 5.90) [91]. [Pg.217]

Two successive Friedel-Crafts alkylation reactions (the first intermolecular and the second intramolecular) will form the desired additional ring. [Pg.691]

Gold-catalyzed direct C-H functionalizations enable the formation of polyalkylated arenes under mild conditions. In many cases, branched products are obtained. Two mechanisms are thought to operate with electron-rich arenes, an S si2-type mechanism via Au(lll) leads to the linear product. The branched product is obtained via a Friedel-Craft-type alkylation. A silver salt is often added and is believed to generate a more electrophilic Au(m) species. Often regioselectivities are poor and symmetric arenes are employed. Intramolecular variants as well as Michael additions are also known (Equations (72)-(74)).71,71a,71b... [Pg.124]

Friedel-Crafts acylation. Posner el al. have developed a remarkably efficient route to the methyl ether of the steroid 11-oxoequilenin (5) from 2-methyl-2-cyclopentenone (1). jS-Addition of the organocoppermagnesium reagent 2 to 1 followed by a-alkylation with ethyl iodoacetate proceeds stereospecifically to give the secosteroid 3 in 94% yield. The final step requires an intramolecular Friedel-Crafts acylation, a reaction that has proved troublesome in previous syntheses of steroids via 9,11-secosteroids. And indeed attempts to cyclize the free acid corresponding to 3 with HF proceeded in yields of 10%. However, cyclization of the ketal acid 4 gives stereochemically pure 5 in 75% yield based on recovered secosteroid. The overall yield from 2-bromo-6-methoxynaphthalene is 52%. [Pg.125]

Titanium tetrachloride promoted a three-component cyclization involving a carbonyl compound, an allylsilane, and an acetal, as shown in Eq. (69) [188]. The reaction was initiated by allyl addition to the aldehyde this was followed by acetal exchange and intramolecular Friedel-Crafts-type alkylation of the olefinic moiety. [Pg.680]

Numerous new examples of cyclopentenone synthesis from acetylenehexacarbonyl-dicobalt complexes and norbornene derivatives have been disclosed there is evidence of steric control, and the bulky trimethylsilyl group can be employed as a removable direction-determining group to allow synthesis of 3- instead of 2-sub-stituted cyclopentenones. Reaction of (731) with sodamide in toluene gave the new octahydro-2,5-methanoazulene system (732 R = CONHj) successive hydrolysis, reduction, and esterification converted (732 R = CONHj) into (732 R = CHjOTs) which, on solvolysis, gave the homoprotoadamantane derivative (733 X = H, R R = CH2) in high yield.The carboxylic acid (732 R = COjH) underwent spontaneous Friedel-Crafts intramolecular acylation on conversion into its acid chloride to give (733 XX = O R R = CHj) and (733 XX = O, R = Cl, R = Me). Reaction of methyl a-bromocrotonate (mixture of E- and Z-isomers) with the enolates of cyclohex-2-enone affords a mixture of stereoisomeric tricyclo-[3,2,l,0 ]octan-6-ones (734 R —R are variously H or alkyl) in moderate yield. The reaction involves double Michael addition and subsequent substitution. [Pg.349]

Subsequently, Hennessy and Buchwald [26] disclosed an intramolecular C-H alkylation affording oxindoles from aelectron-deficient arenes, reflecting the complementary scope of this reaction with the traditional Friedel-Crafts reaction. The basic reaction conditions also allowed the use of functional groups that are incompatible with strong Lewis acids. On the basis of the kinetic isotope effects (KIEs), three different mechanisms were proposed with a common initial step of oxidative addition, which... [Pg.1436]


See other pages where Intramolecular, addition Friedel-Crafts alkylation is mentioned: [Pg.27]    [Pg.156]    [Pg.586]    [Pg.89]    [Pg.68]    [Pg.154]    [Pg.522]    [Pg.372]    [Pg.1304]    [Pg.409]    [Pg.1304]    [Pg.53]    [Pg.73]    [Pg.205]    [Pg.62]    [Pg.139]    [Pg.150]    [Pg.34]    [Pg.636]    [Pg.754]    [Pg.754]    [Pg.1342]    [Pg.152]    [Pg.156]    [Pg.403]    [Pg.352]    [Pg.754]   
See also in sourсe #XX -- [ Pg.706 ]




SEARCH



Addition alkylation

Alkylation intramolecular

Alkylative addition

Friedel Crafts alkylation

Friedel intramolecular

Friedel-Crafts addition

Friedel-Crafts alkylations

Intramolecular Friedel-Crafts

Intramolecular Friedel-Crafts alkylation

Intramolecular addition

Intramolecular alkylations

© 2024 chempedia.info