Big Chemical Encyclopedia

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

Articles Figures Tables About

Indoles Friedel-Crafts alkylation

Furthermore, Jana et al. developed a FeCl3-catalyzed C3-selective Friedel-Crafts alkylation of indoles, using allylic, benzylic, and propargylic alcohols in nitromethane as solvent at room temperature. This method can also be used for the alkylation of pyrrole (Scheme 4). The reactions were complete within 2-3 h without the need of an inert gas atmosphere leading to the C-3-substitution product exclusively in moderate to good yields [20]. [Pg.5]

Scheme 4 FeCb catalyzed Friedel-Crafts alkylations of indoles with alcohols... Scheme 4 FeCb catalyzed Friedel-Crafts alkylations of indoles with alcohols...
Fig. 34 Catalytic asymmetric Friedel-Crafts alkylation of indoles catalyzed by 60... Fig. 34 Catalytic asymmetric Friedel-Crafts alkylation of indoles catalyzed by 60...
Pseudo-C3-symmetrical trisoxazoline copper(II) complexes prove to be excellent catalysts in the Friedel-Crafts alkylation of indoles with alkylidene malonates (Eq. 7.13). Water tolerance of chiral catalyst trisoxazoline/Cu(OTf)2 was examined, and it was found that the addition of up to 200 equivalents of water relative to the catalyst in /,vo-butyl... [Pg.206]

The C2-symmetric bifunctional tridentate bis(thiazoline) 222 has been shown to promote the zinc(II)-catalyzed asymmetric Michael addition of nitroalkanes to nitroalkenes in high enantioselectivity <06JA7418>. The corresponding bis(oxazoline) ligand provides comparable enantioselectivity but higher product yield. The same bis(thiazoline) ligand has also been evaluated in the enantioselective Friedel-Crafts alkylation of indoles, but the enantioselectivity is moderate <06OL2115>. [Pg.261]

Two years after the discovery of the first asymmetric Br0nsted acid-catalyzed Friedel-Crafts alkylation, the You group extended this transformation to the use of indoles as heteroaromatic nucleophiles (Scheme 11). iV-Sulfonylated aldimines 28 are activated with the help of catalytic amounts of BINOL phosphate (5)-3k (10 mol%, R = 1-naphthyl) for the reaction with unprotected indoles 29 to provide 3-indolyl amines 30 in good yields (56-94%) together with excellent enantioselec-tivities (58 to >99% ee) [21], Antilla and coworkers demonstrated that A-benzoyl-protected aldimines can be employed as electrophiles for the addition of iV-benzylated indoles with similar efficiencies [22]. Both protocols tolerate several aryl imines and a variety of substituents at the indole moiety. In addition, one example of the use of an aliphatic imine (56%, 58% ee) was presented. [Pg.406]

In 2007, two groups independently described asymmetric phosphoric acid-catalyzed Friedel-Crafts alkylations of indoles. While You et al. chose the conventional approach and employed imines as substrates (Scheme 11), Terada and coworkers came up with a different concept and used electron-rich alkenes as precursors (Scheme 49) [73]. Enecarbamates 125 reacted with indoles 29 in the presence of BINOL phosphate (R)-io (5 mol%, R = bearing 2,4,6-triisopropyl-... [Pg.434]

Scheme 50 Friedel-Crafts alkylation of indoles with ( )- or (Z)-enecarbamates... Scheme 50 Friedel-Crafts alkylation of indoles with ( )- or (Z)-enecarbamates...
Shortly after the discovery of the first asymmetric phosphoric acid-catalyzed transformation of enecarbamates, Zhou et al. expanded the scope of the Friedel-Crafts alkylation of indoles 29 with electron-rich alkenes to enamides 127 (Scheme 51) [74],... [Pg.435]

Akiyama and coworkers extended the scope of electrophiles applicable to asymmetric Brpnsted acid catalysis with chiral phosphoric acids to nitroalkenes (Scheme 57). The Friedel-Crafts alkylation of indoles 29 with aromatic and aliphatic nitroalkenes 142 in the presence of BINOL phosphate (7 )-3r (10 mol%, R = SiPhj) and 3-A molecular sieves provided Friedel-Crafts adducts 143 in high yields and enantioselectivities (57 to >99%, 88-94% ee) [81]. The use of molecular sieves turned out to be critical and significantly improved both the yields and enantioselectivities. [Pg.440]

Scheme 6.7 Product range of 9- and urea 16-catalyzed Friedel-Crafts alkylations of indole and methyl indoles. Scheme 6.7 Product range of 9- and urea 16-catalyzed Friedel-Crafts alkylations of indole and methyl indoles.
Scheme 6.148 Product range of the enantioselective 139-catalyzed Friedel-Crafts alkylations of various indols. The product configurations were not determined. Scheme 6.148 Product range of the enantioselective 139-catalyzed Friedel-Crafts alkylations of various indols. The product configurations were not determined.
Figure 6.46 (A) Hydroxy-protected thiourea 141 and 142 lacking the hydroxy function and their catalytic efficiency in the Friedel-Crafts alkylation of indole with frans-P-nitrostyrene (139 78% yield 85% ee under identical conditions). (B) Proposal for the key hydrogen-bonding interactions between 139 and the model substrates. Figure 6.46 (A) Hydroxy-protected thiourea 141 and 142 lacking the hydroxy function and their catalytic efficiency in the Friedel-Crafts alkylation of indole with frans-P-nitrostyrene (139 78% yield 85% ee under identical conditions). (B) Proposal for the key hydrogen-bonding interactions between 139 and the model substrates.
The first, and one of the most straightforward, syntheses of racemic 69 was that of Schach von Wittenau and Els ° after they had determined the stmcmre. Friedel-Crafts alkylation of indole with ethyl 2,3-epoxybutyrate gave the a-indolmycenic acid ester 119a. Cyclization of 119a with Af,//-dimethylguanidine yielded both 69 and isoindolmycin 120 (Scheme 6.32). In this case, facile epimerization of H-5 had occurred under the basic cyclization conditions. [Pg.79]

Alkylation of 2,3-disubstituted indoles generally leads to the formation of 2,3,3-trisub-stituted 3H-indoles, but it has been claimed that if the six-membered ring is activated to electrophilic attack, Friedel-Crafts alkylation occurs at the 5- or 6-positions (79MI30500). [Pg.226]

HF calculations with the 6-31G(d) basis set were used to study the mechanism of the Michael addition (or Friedel-Crafts alkylation) reaction of indole with dimethyl alkylidenemalonate. This reaction proceeds through two transition states, TSi and TS2 in the first step, assumed to be rate determining, the new C-C bond is formed, whereas in the second step, proton transfer from indole to malonate occurs with the formation of the new C-H bond. The calculations show that the transfer and interaction of the 7r-electrons in the reactant molecules may play an important role in the cleavage of the original C=C bond and the formation of the new bonds (C-C and C-H) the electron transfer is believed to be the driving force for the reaction to occur. [Pg.349]

Chiral bis-sulfonamides 162-163 are a new group of organo catalysts for the enantioselective Friedel-Crafts alkylation of indoles to nitroolefins. The hy-... [Pg.27]

As indicated from computational studies, the catalyst-activated iminium ion MM3-2 was expected to form with only the (E)-conformation to avoid nonbonding interactions between the substrate double bond and the gem-dimethyl substituents on the catalyst framework. In addition, the benzyl group of the imidazolidinone moiety should effectively shield the iminium-ion Si-face, leaving the Re-face exposed for enantioselective bond formation. The efficiency of chiral amine 1 in iminium catalysis was demonstrated by its successful application in several transformations such as enantioselective Diels-Alder reactions [6], nitrone additions [12], and Friedel-Crafts alkylations of pyrrole nucleophiles [13]. However, diminished reactivity was observed when indole and furan heteroaromatics where used for similar conjugate additions, causing the MacMillan group to embark upon studies to identify a more reactive and versatile amine catalyst. This led ultimately to the discovery of the second-generation imidazolidinone catalyst 3 (Fig. 3.1, bottom) [14],... [Pg.97]

The use of other nucleophilic species to perform Friedel-Crafts alkylations to a,/ -unsaturated aldehydes has also been investigated, with success. For example, indoles [14, 83] and anilines [18, 84] have been added to a,/ -unsaturated aldehydes, providing 1,4-addition products in good yields and excellent enantioselec-tivities. Again, the importance of such an approach is demonstrated by the suc-... [Pg.107]

For computational studies on the Friedel-Crafts alkylation of pyrroles and indoles catalyzed by chiral imidazolidinones, see R. Gordillo, J. Carter, K.N. Houk, Adv. Synth. Catal. [Pg.119]

Jorgensen and co-workers employed chiral bis-sulfonamide catalyst 27, a proven ligand for metal-based asymmetric catalysis, for the Friedel-Crafts alkylations of N-methylindoles (24) using -substituted nitroolefins [52]. Using optimized conditions, 2 mol% 27 gave the desired indole alkylation products of substituted aryl and heteroaryl nitroolefins in moderate to high yields (20-91%) and moderate enantiopurities (13-63% ee Scheme 6.3). Aliphatic -substitution... [Pg.202]

Table 6.9 Thiourea-catalyzed Friedel-Craft alkylations of indoles. Table 6.9 Thiourea-catalyzed Friedel-Craft alkylations of indoles.
Explain the formation of the product in this Friedel-Crafts alkylation of an indole. [Pg.1182]

The Friedel-Crafts alkylation of the parent pyrrole and of substituted indoles with a,P-unsaturated acyl phospho-nates 468 <2003JA10780> and 2-acyl iV-methylimidazoles 469 catalyzed by the chiral bis(oxazolinyl)pyridine (pybox)/scandium(lIl) triflate complex 467 exhibits good enantioselectivities over a broad range of substrates (Scheme 97, Equation 113) <2005JA8942>. The desired alkylation products 470-472 were formed in good yields and enantioselectivities. [Pg.116]

Enantioselective Friedel-Crafts alkylation of A -benzylpyrrole and 5-nitroindole with benzoylhydrazones 504 promoted by a simple strained silacycle reagent 505 gives 2- and 3-derivatives 506 and 507, respectively (Scheme 102) <2005JA2858>. Indole itself provides the corresponding product with significantly reduced enantioselectivity (ee 24%). [Pg.120]

Friedel-Crafts Alkylation Reactions. The activation of glyoxylate esters,trifluoromethyl pyruvate esters, and unsaturated a-ketoesters by catalyst 2 converts these materials into effective electrophiles for asymmetric Friedel-Crafts alkylation reactions with activated arenes (eqs 16 and 17). In fact, bis(triflate) (2) is far superior to tbe bis(hexafluoroantimonate) complex at catalyzing the enantioselective alkylation of benzene derivatives. Aniline and anisole derivatives both give the reaction, as do heterocyclic aromatic compounds such as indole and furan. [Pg.422]


See other pages where Indoles Friedel-Crafts alkylation is mentioned: [Pg.162]    [Pg.155]    [Pg.406]    [Pg.407]    [Pg.444]    [Pg.154]    [Pg.159]    [Pg.224]    [Pg.324]    [Pg.21]    [Pg.201]    [Pg.224]    [Pg.324]    [Pg.544]    [Pg.202]    [Pg.255]    [Pg.298]   
See also in sourсe #XX -- [ Pg.162 ]




SEARCH



3-Alkyl indoles

Alkylation indole

Friedel Crafts alkylation

Friedel Crafts indole

Friedel-Crafts Indoles

Friedel-Crafts alkylation of indoles with nitroalkenes

Friedel-Crafts alkylations

Indoles 3- alkylated

Indoles Friedel-Crafts alkylations

Indoles alkylate

Indoles alkylation

Indoles alkylations

© 2024 chempedia.info