Friedel-Crafts alkylation intramolecular

Ferrocene Bisimidazoline Platinacycle-Catalyzed Intramolecular Friedel-Crafts Alkylations... 

Highly reactive mixed anhydrides can also promote acylation. Phenylacetic acid reacts with alkenes to give 2-tetralones in TFAA-H3P04.55 This reaction involves an intramolecular Friedel-Crafts alkylation subsequent to the acylation. 

A fourfold anionic sequence which is not initiated by a Michael but an aldol reaction has been reported by the group of Suginome and Ito (Scheme 2.129) [295]. In this approach, the borylallylsilane 2-573 reacts selectively in the presence of TiCl4 with two different aldehydes which are added sequentially to the reaction mixture. First, a Lewis acid-mediated allylation of the aldehyde with 2-573 takes place to form a homoallylic alcohol which reacts with the second aldehyde under formation of the oxenium ion 2-574. The sequence is terminated by a Prins-type cyclization of 2-574 and an intramolecular Friedel-Crafts alkylation of the intermediate 2-575 with formation of the fraws-1,2-be rizoxadeca lines 2-576 as single diastereomers. 

From a mechanistic point of view, it can be envisaged that this reaction proceeds via the desired benzylated pentanedione intermediate 14f. The subsequent intramolecular Friedel-Crafts alkylation of the electron-rich arene results in the quaternary benzyl alcohol II, which readily eliminates water to give the highly substituted indene 16 (Scheme 14). 

Subsequent intramolecular Friedel-Crafts alkylation and elimination yields the coumarin derivatives (See Scheme 14, Sect. 2.2). With 5 mol% of BiCl3, the desired products 21a-d have been obtained in high yields after short reaction times (1-2 h) (Scheme 17). 

Similar to Rueping s procedure, Hua and coworkers developed a BiCl3-catalyzed synthesis of 1,1-diarylalkanes also starting from electron-rich arenes and styrenes [68]. They found that styrenes 37 could be transformed to the substituted cyclopentanes 39 if catalytic amounts BiCl3 were applied (Scheme 30). This reaction is believed to proceed via an intermolecular ene-reaction between styrene and the carbocationic intermediate I, followed by an intramolecular Friedel-Crafts alkylation of the resulting intermediate II. 

We have found that intramolecular Friedel-Crafts alkylations of conjugated dienones permit the efficient preparation of functionalized hydrophenanthrenes (Equation 5.1).21 Since this represents a new strategy for the synthesis of 6,6,6-fused tricycles, we sought to demonstrate its utility through the total syntheses of miltirone (56) and two closely related diterpenoids sageone (57), which possesses significant antiviral activity,22 and arucadiol (58), 23... 

An intramolecular Friedel-Crafts alkylation to prepare functionalized hydrophenanthrenes. (From Majetich, G., Liu, S., Fang, J., Siesel, D., and Zhang, Y.,. Org. Chem.., 1997, 62, 6928. With permission.)... 

An intramolecular Friedel-Crafts alkylation reaction follows, in which the carbocation attacks the adjacent aromatic ring. 

Propargylic silyl ethers 588 undergo intramolecular Friedel-Crafts alkylation to afford 4-allenyl isochromans 589 in excellent yield (Equation 243) <2001JOC4635>. 

The third possibility for a selective monoalkylation is provided by intramolecular Friedel-Crafts alkylations. There are no multiple alkylations simply because all electrophilic centers react most rapidly intramolecularly (i.e., only once). Friedel-Crafts alkylations of this type are ring closure reactions. 

Again, % electrons are involved, but the reaction is now electrophilic aromatic substitution (Chapter 22) rather like an intramolecular Friedel-Crafts alkylation with a delocalized intermediate often termed a phenonium ion. 

This intramolecular Friedel-Crafts alkylation is an example. 

The indane structure is formed by an intramolecular Friedel-Crafts alkylation. To prevent intermolecular alkylation and standard vinyl polymerization, respectively, the polymerization is performed at high dilution and above the monomer s ceiling temperature. 

When the Hammett plot bends the other way, so that the rate of the reaction decreases as it passes the discontinuity, we have a single mechanism with a change in rate-determining step. A reaction goes by the fastest possible mechanism but its rate is limited by the slowest of the steps in that mechanism. An example is the intramolecular Friedel-Crafts alkylation of a diphenyl derivative where the alkylating agent is a diaryhnethanol attached to one of the benzene rings in the ortho position. 

An intramolecular Friedel-Crafts alkylation of the 2-alkylidene branched 1,3-dithiole (159) leads to l,l-bis(organothio)tetralines (160) (Equation (28)) <78BCJ2674>. 

The next step is a simple electrophilic attack by another molecule of formaldehyde on the alkene - in other words a simple Prins reaction 215 - showing the regioselectivity we expect to produce the secondary benzylic cation 216. The second molecule of formaldehyde has added onto the opposite side from the first. The resulting cation is perfectly placed for an intramolecular Friedel-Crafts alkylation 216 of the benzene ring. This is again a stereoselective reaction giving the more stable anti diastereoisomer 214. This sequence involves three successive C-C bondforming reactions and the stereochemistry is simply controlled by the preference for the more stable anti product. 

Under Lewis acidic conditions, cyclic acetals such as 72a-b form oxonium ion intermediates which cyclize via an intramolecular Friedel-Crafts alkylation onto the tethered arene to form polycyclic benzylic ethers, Eq. 57 [85]. 

The main synthesis of oxindoles is simple and direct and involves an intramolecular Friedel-Crafts alkylation reaction as the cyclising step. Also straightforward in concept is the displacement of halogen from an ort/to-halo-nitroarene with malonate, this leading to an oxindole after decarboxylation and reduction of the nitro group with spontaneous lactamisation. ... 

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. ... 

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