Coupling with aromatic chlorides

Dehydrohalogenation of the 314 proceeded in excellent yield under the action of morpholine or piperidine at rt, during double bond formation between the C-l and C-2 atoms <2003CHE640>. The active methylene group of 3,4-dihydro-1 ///>//-[ 1,4 oxazino[3,4- quinazolin-6-onc 315 readily condensed with aromatic aldehydes at 160 °C in a melt to give the 1-benzylidenes, and coupled with aryldiazonium chlorides to give the arylhydrazono derivatives <1996BMC547>. 

The chlorinated intermediate 255 is eliminated and cycloadds to Cjq, yielding pyrazo-linofullerenes of the structure 257 (Scheme 4.42). The 4-nitrophenyl-group can be replaced by a 4-methoxyphenyl- or a phenyl substituent. In this reaction various aromatics and substituted aromatics are tolerated as residues R (e.g. furan, ferrocene, pyrazole or benzene and substituted benzene). The nitro group of the nitrophenyl residue can be reduced with Sn-HCl to the aniline derivative, which can be further functionalized by amide coupling with acid chlorides [311]. 

Dyes containing the pyridinium group linked to the diazo component via a carboxylic ester function (e.g., 40) [32017-47-3] are obtained by condensation of 4-nitrobenzoyl chloride with chloroethanol, reaction of the ester with pyridine, reduction of the nitro to an amino group, diazotization, and coupling with aromatic amines [124],... 

The behavior of bis(heteroaryl)methanes in which the heterocycle was an electron-withdrawing group was similar to that typically exhibited by active methylene compounds. Bis(2-benzothiazolyl)methane and bis(2-(5-ethoxycarbonyl-4-methyl)thiazolyl)methane readily underwent azo-coupling with benzenediazonium chloride, nitrosation with nitrous acid and condensation with aromatic aldehydes under mildly basis conditions, such as in the Knoevenagel procedure. [94G301]... 

Another synthesis of u-triazolo[4,5-d]p5nrimidines described first by Benson et and by Hartzel and Benson also involves closing the triazole ring. It proceeds from a derivative of 4-aminopyrimidine (166), and making use of the aromatic character of the 5-position in the pyrimidine nucleus produces 4-amino-5-arylazo derivatives (167) by coupling with benzenediazonium chloride. These derivatives under-... 

Aryl chlorides are more reluctant to undergo amination than most other aryl halides/pseudohalides. To address this problem, Caddick and coworkers investigated the outcome of palladium-N-heterocyclic carbenes as catalysts in rapid microwave promoted reactions [121]. para-Tolyl and para-anisyl chloride were coupled with aromatic and aliphatic amines in generally good yields within 6 min at 160 °C. Reactions between tolyl/anisyl/phenyl chlorides and aliphatic amines have also been reported by Maes et al. using a more classic reaction system with a phosphine ligand and a strong base the reaction afforded the desired products after 10 min irradiation at 110-200 °C [122]. 

Cross-coupling of heteroarylzincs such as 2-pyridyl- or 2-thiofuranylzincs with aromatic chlorides can also be achieved. The combination of Pd2(dba)j (2 mol%) and the bulky electron-rich ligand XPhos (193) (8mol%) provides a competent catalyst to achieve this transformation in high yields, as shown for the preparation of 192 from 190 with 191 [160] (Scheme 4.43). 2-Pyridylzinc chloride also reacts... 

Scheme 4.43 Pd-catalyzed cross-coupling of 2-thiophenylzincs with aromatic chlorides [160].

These arylzincs formed in these conditions do not lead to aromatic ketones when they are coupled with acetyl chloride using a mixture of cuprous cyanide and lithium chloride, as previously described by Knochel [42]. Therefore, electrogenerated organozinc species and acyl chlorides are coupled using a palladium(II) catalysis quantitatively (Eq. (25)) [43]. Overall yields and subsequently isolated yields are good (64—76%) ... 

Arenediazonium salts are also used for the couplina[563], (Z)-Stilbene was obtained unexpectedly by the reaction of the ti-stannylstyrene 694 by addition-elimination. This is a good preparative method for cu-stilbene[564]. The rather inactive aryl chloride 695 can be used for coupling with organostannanes by the coordination of Cr(CO)3 on aromatic rings[3.565]. 

Substituted aroyl- and heteroaroyltrimethylsilanes (acylsilanes) are prepared by the coupling of an aroyl chloride with (Me3Si)2 without decarbonylation, and this chemistry is treated in Section 1.2[629], Under certain conditions, aroyl chlorides react with disilanes after decarbonylation. Thus the reaction of aroyl chlorides with disilane via decarbonylation is a good preparative method for aromatic silicon compounds. As an interesting application, trimel-litic anhydride chloride (764) reacts with dichlorotetramethyidisilane to afford 4-chlorodimethylsilylphthalic anhydride (765), which is converted into 766 and used for polymerization[630]. When the reaction is carried out in a non-polar solvent, biphthalic anhydride (767) is formed[631]. Benzylchlorodimethylsilane (768) is obtained by the coupling of benzyl chloride with dichlorotetramethyl-disilane[632,633]. 

Reference methods for criteria (19) and hazardous (20) poUutants estabHshed by the US EPA include sulfur dioxide [7446-09-5] by the West-Gaeke method carbon monoxide [630-08-0] by nondispersive infrared analysis ozone [10028-15-6] and nitrogen dioxide [10102-44-0] by chemiluminescence (qv) and hydrocarbons by gas chromatography coupled with flame-ionization detection. Gas chromatography coupled with a suitable detector can also be used to measure ambient concentrations of vinyl chloride monomer [75-01-4], halogenated hydrocarbons and aromatics, and polyacrylonitrile [25014-41-9] (21-22) (see Chromatography Trace and residue analysis). 

Oxidative coupling of aromatic compounds via the SchoU reaction has been appHed successhiUy to synthesise a polyarylethersulfone (18). High molecular weight polymer was obtained upon treating 4,4 -di(l-naphthoxy)diphenylsulfone and 4,4 -di(l-naphthoxy)ben2ophenone with ferric chloride. Equimolar amounts of the Lewis acid are required and the method is limited to naphthoxy-based monomers and other systems that can undergo the SchoU reaction. 

Diphenylcinnoline can be prepared from benzil monophenylhydrazone in the presence of about 80% sulfuric acid (49MI21200). Synthetically more important, however, is the cyclization of mesoxalyl chloride phenylhydrazones under Frledel-Crafts -conditions (61JCS2828). As outlined in Scheme 67, the starting mesoxalate phenylhydrazones are obtained by coupling dlazotized aromatic amines with diethyl malonate. After conversion... 

Pyrazolediazonium salts (448) couple with activated aromatic molecules, like naphthols (79KGS805), and can be reduced to hydrazines (452) with tin(II) chloride (74MI40406). 

In the first of these, the key step in the synthetic sequence involves an oxidative phenol coupling reaction patterned after the biosynthesis of the natural product. Preparation of the moiety that is to become the aromatic ring starts by methyla-tion of phloroglucinol (5) with methanolic hydrogen chloride to give the dimethyl ether (6). Treatment of that intermediate with sulfuryl chloride introduces the chlorine atom needed in the final product (7). 

Arylamines are converted by diazotization with nitrous acid into arenediazonium salts, ArN2+ X-. The diazonio group can then be replaced by many other substituents in the Sandmeyer reaction to give a wide variety of substituted aromatic compounds. Aryl chlorides, bromides, iodides, and nitriles can be prepared from arenediazonium salts, as can arenes and phenols. In addition to their reactivity toward substitution reactions, diazonium salts undergo coupling with phenols and arylamines to give brightly colored azo dyes. 

Aromatic nitro compounds are reduced to the corresponding amines by tin(II) chloride in acidic medium. These are then diazotized via the gas phase with nitrous fumes and finally coupled with 1-naphthol to yield an azo dye. 

The dinitrophenyl derivatives are reduced by titanium(III) chloride in acidic medium in the first step of the reaction to the corresponding aromatic amines these are then diazotized and coupled with N-(l-naphthyl)-ethylenediamine to yield an azo dye (cf. Fig. 21). 

All examples mentioned so far correspond to reactions between two aromatic groups, however, couplings in which one or both partners are alkyl groups can be achieved using electron-rich boron-based nucleophiles. Fiirstner has reported the use of B-alkyl or 5-allyl methoxy-9-BBN anions for the efficient coupling with some aryl chlorides using an in situ prepared IPr HCl/Pd(OAc)j system [118], Some of the results obtained with these easy-to-handle borate-based nucleophiles are shown below (Scheme 6.34). 

---