Friedel-Crafts arylations

Hall-Petch relationship, 13 497 Haloacetic acids (HAAs), removal from drinking water, 17 806—807 Haloacetones, 1 163 Haloalkylating agents, 12 167 Haloalkylation, 12 166-168 Haloalkylbenzenes, intramolecular alkylation of, 12 169 IV-Halo-a-amino acids, 13 107 Haloaromatics, 13 573 Halobenzenes, as Friedel-Crafts arylating agents, 12 171 Halobismuthines, 4 28-29 Haloboration, 14 270 Halobrom (BCDMH,... 

A second example from the same group is the synthesis of an elaborate diethynyltriphenylene derivative (Scheme 7 Table 8,entries 12,13) [58].Zn/Pd-promoted homocoupling of a 4-iodo-l,2-dialkoxybenzene furnishes the desired tetraalkoxybiphenyl, an electron-rich aromatic system. Iron trichloride-catalyzed Friedel-Crafts arylation of the biphenyl derivative with dimethoxy-benzene furnishes an unsymmetrical triphenylene derivative. Deprotection, oxidation, and subsequent Diels-Alder reaction with cyclohexadiene is followed by catalytic hydrogenation and reoxidation. TMS-CC-Li attack on the quinone delivers the alkyne modules, treatment with SnCl2 aromatizes the six-mem-bered ring, while KOH in MeOH removes the TMS groups cleanly to give the elaborate monomer. 

In contrast to the organo lithium and Grignard reagents Friedel-Crafts arylation reactions occur quite cleanly with N3P3CI6, while unsubstituted fluorocyclophosphazenes do not undergo Friedel-Crafts arylation at all [1,13]. Friedel-Crafts arylation predominantly results in geminal products irrespective of the starting cyclophosphazene (Eq. 42) [229] ... 

An extensive study of the Friedel-Crafts phenylations of a wide variety of aminophosphazenes have been conducted [230-233]. Reactions at the PCI2 centre is generally sluggish. With the bulky secondary amino derivatives, hydrocarbon formation is the competing process [232]. Aryl fluorophosphazenes undergo Friedel-Crafts arylation readily [182, 234-236]. These reactions have been used to convert a P(Ar)F centre to a P(Ar)(Ar ) centre (Eqs. 43,44) [234]. 

A -Acylamino aromatic ketones 790 can be prepared by arylation of saturated oxazolones in the presence of Lewis acids. Cyclodehydration of 790 leads to 2,5-diaryloxazoles 791. For example, saturated 5(4//)-oxazolones 789 from 7/-benzoyl-alanine or A-benzoylvaline undergo Friedel-Crafts arylation to afford substituted A-benzoylphenacylamines 790. In the presence of POCI3, 790 cyclizes to produce 5-aryl-2-phenyloxazoles 791 (Scheme 7.241). ... 

Friedel-Crafts Arylation. The Scholl Reaction De-hydrogen-coupling... 

In addition to undergoing Friedel-Crafts arylations, cyanuric chloride has been used in the Friedel-Crafts synthesis of (67) from pyridine (equation 31) (68ZOB1368). 

The caged species may escape geminate recombination and produce various species that can initiate cationic polymerization. Solvent (RH) often participates in these reactions producing protonic acids. As shown in Eq. (44), protonic acids are also formed by reaction of radical cations with aryl radicals or by Friedel-Crafts arylation. Up to 70% of the protonic acid is formed upon photolysis of diaryliodonium salts [205]. In addition to initiation by protons, arenium cations and haloarene radical cations can react directly with monomer. The efficiency of these salts as cationic initiators depends strongly on the counterions. Those with complex anions such as hexafluoroantimonate, hexafluorophosphate, and triflate are the most efficient. 

Friedel-Crafts Arylation with Phosphorus Chlorides... 

Functionahzation of Ceo through bond formation has been achieved by a variety of methods nucleophihc addition of carbanions, quenching of Ceo anions with alkyl hahdes, Friedel Crafts arylation, radical addition, and cycloadditions. 

Various carbon-carbon cross-coupling reactions are employed to arrive at oligomers from fluorene monomers, including nickel-cataylzed Yamamoto coupling between aryl halides [48], palladium(0)-catalyzed Suzuki coupling between boronic acids/esters and halides [49], and ferric-chloride-catalyzed Scholl reaction, also called Friedel-Crafts arylation, of bare fluorenes [50,51]. 

The literature includes a Friedel-Crafts arylation of triazine 279 to yield 280 (83KGS1125). 

The commercial product contains hydrocarbon-type impurities due to further Friedel-Crafts arylation of methoxychlor during manufacture such as 20 and 21. Photo closure of 21 yields the phenantrene 22, which on further oxidative closure gives the dibenzochrysene 23 (Mitchell and West, 1978). 

Silyl enol ethers (CHj = CROSiMe3) react with cyanuryl chloride and replace only one chlorine with a carbon substituent (CH2COR R = cyclopropyl, 70 /o, R = Ph, 90 /o). Friedel-Crafts arylation <83KGS1125,92EUP497734>, the Ullmann reaction of 2-iodo-1,3,5-triazine to form 2,2 -bis-1,3,5-triazine <82NKK1425>, and a palladium-catalyzed cross-coupling reaction of 2-substituted 4,6-dichloro-... 

The additions of thiols and sulphenyl chlorides to alkenylphosphonic derivatives to yield (2-alkylthioethyl)phosphonic compounds are reactions which have already been noted" Dialkyl (alkylthiomethyl)phosphonates yield a-chloro derivatives when treated with ncs in CCl/° the resultant dialkyl (l-alkylthio-l-chloromethyl)phosphonates undergo Friedel-Crafts arylation with benzene, alkylbenzenes or other activated aromatics in the presence of SnCl4 or TiCl/ yields are said to be good. 

Metal-Catalyzed Enantioselective Friedel-Crafts Arylations... 

Several examples of metal-catalyzed enantioselective Friedel-Crafts arylations to conjugated acceptor systems are known. Similar to the 1,2-addition reaction, most of the substrates are bidentate in nature to ensure a tight-binding, rigid metal-substrate interaction (Figure 8.11). 

Figure 8.12 Metal-bisoxazoline complexes catalysts for Friedel-Crafts arylations.

Scheme 8.51 Organocatalytic Friedel-Crafts arylations by chiral phosphoric acids.

Scheme 8.52 Organocatalytic Friedel-Crafts arylations of a,P-unsaturated aldehydes.

Scheme 8.53 Enantioselective Friedel-Crafts arylation of a,P-unsaturated ketones 202.

The Scholl reaction, formally representing a Friedel-Crafts arylation reaction, is the aryl-aiyl coupling of two aromatic species 1 via dehydrogenation under Lewis acid and protic acid conditions. 

Methyl-l-phenylhept-3-yne-2,6-diol undergoes a one-pot three-step cascade reaction with alkyl and aryl aldehydes to provide 2,4-dihydro-lH-benzo[ isochromans.This two-component cascade reaction promoted by Bp3-OEt2 involves an alkynyl-Prins cyclization, Friedel-Crafts arylation, and dehydrative aromatization (130L4070). Other Prins cascade cycliza-tions of 2-arylethylbut-3-en-l-ol with aliphatic and aromatic aldehydes occur in the presence of Sc(OTf)3 andp-TsOH to prepare trans-fused hexa-hydro-1 H-benzo[ isochromans in good yields and excellent selectivity (Scheme 44) (13EJ01993). 

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