Bromoanilines

Kuroda and Suzuki used reaction of 267a with 2-bromoaniline leading to anilide 312 as the first step of their sequence in the preparation of 1H-imidazo[4,5-c]quinolin-4(5//)-ones (Scheme 77) (91TL6915). Reaction of 267a with amines usually does not require any catalyst and/or base, but in this case use of sodium hydride was reported. The anilide 312 was sequentially alkylated, first with methyl iodide in ethanol with potassium hydroxide at room temperature and then with different alkyl iodides in acetone at reflux to provide intermediate 313. This compound was then cyclized via palladium catalyzed reaction leading to product 314. This reaction provides a new entry to l//-imidazo[4,5-c]quinolin-4(5//)-ones that are of current interest as antiasthmatic agents. 

H. Tanaka, O. Ren, S. Torii, Pd(0)/Pd(II)-mediated electroreductive cyclization of n-alkenyl-2-bromoanilines in Novel Trends in Electroorganic Synthesis (Ed. S. Torii), Kodansha, Tokyo, 1995, pp. 195,196. 

Palladium complexes have been used for the electroreductive cycliza-tion of Ai-alkenyl-2-bromoanilines to the corresponding indoline derivatives (Scheme 69) [101]. The postulated carban-ion intermediate undergoes a reaction with the electrophiles (H+, CO2). 

Some breakthrough was finally achieved by using Pd2(dba)3 as the Pd complex, tris(tert-butyl)phosphine as the ligand, and sodium ferf-butoxide as the base [90]. This combination of reagents proved to bring about the synthesis of unsubstituted phenazine (137) by reaction of two molecules of 2-bromoaniline (131). Remarkably, no reaction takes place under the conditions of the 133 117 transformation. Currently the scope and limitations of this new sequential inter-Zintramolecular AT-arylation for the synthesis of AT-heterocycles... 

We can also mention that one example of electroreductive cyclization of N-alkenyl-2-bromoanilines has recently been reported using Pd-PPhs as catalyst [79]. 

The facile formation and ring closure of enamines has also been exploited in the solid-phase preparation of indolecarboxylates. Attachment of 2-iodoaniline or 2-bromoaniline to the resin in the form of an or-anilino-acrylate followed by the palladium catalysed formation of the five... 

Copper-catalyzed coupling reaction of 2-bromoanilines and pipecoli-nic acid provided 6,6fl,7,8,9,10-hexahydro-5H-pyrido[l,2-a]quinoxalin-6-ones 392 (09BML4119). Using [Pd(r/3-C3H5)Cl2]2 with (2-biphenyl)di-ferf-butylphosphine catalyst system and Cu(I)Br gave lower yields. 

Indole synthesis.9 A new route to 2-substituted indoles is based on the Pd(0) coupling of alkynylstannanes with 2-bromoanilines or 2-trifloxyanilines to give 2-alkynylanilines. Intramolecular cyclization of these products with a variety of Pd(II) catalysts provides substituted indoles. 

The palladium(0)-catalyzed borylation/Suzuki coupling protocol was developed by Baudoin and co-workers in order to synthesize sterically hindered 2,2 -disubstituted biaryl compounds such as 170 in high yield and in a convenient manner [162,163], Indeed, the catalytic borylation of 2-bromoaniline 167 (R=H) gave the corresponding pinacolboronic ester 168 which was reacted in a one-pot fashion with phenyl iodide 169 in the presence of barium hydroxide to give the functionalized biphenyl 170 in 78% yield. Cleavage of the MOM group and cyclization in the presence... 

The phototransformation of aqueous 2-chloroaniline was studied by Oth-men and Boule by means of product analysis [47] these authors later deepened and extended their work, including also 2-fluoro- and 2-bromo-aniline [48]. The range of photodegradation quantum yields was

[Pg.172]

In our group we have also developed the carbolithiation reaction of lithiated double bonds by aryllithium species. Thus, treatment of different Af-2-bromoallyl-2-bromoanilines... 

Indole derivatives have been prepared by reaction of 2-bromoanilines with enamines in the presence of palladium(II) acetate127, reductive cyclization onto a nitro group128, or by the same type of cycloaddition that allows the synthesis of benzofuranols (see above) but using / -quinone diimides129. An example of an application of this latter method is the regioselective nucleophilic addition of 1-piperidino-l-propene (245) to the selectively activated AT4-(phenylsulfonyl)-p-quinone diimide 244 (equation 51)130. Fur-... 

Metalation of the amine substrate 184, followed by annulation promoted by tetramethylethylenediamine (TMEDA), gave the intermediate 185, which could thereafter be converted to the fused 3-pyrroline system 186 (Scheme 22). Subsequent dehydrogenation with DDQ gave the corresponding fused pyrrole. This methodology was used for preparation of an extended set of related pyrroles, as well as a series of indole derivatives, which were accessed by lithiation of iV-bromoallyl-2-bromoanilines <2001CEJ2896>. 

A palladium-catalyzed amination of triflate 111 with 2-bromoaniline 112, followed by an intramolecular Heck-reaction gave the P-carbolinone 113 <03OL4195>. 

Dimerization of 2-bromoaniline in nitrobenzene with anhydrous potassium carbonate and copper powder also affords phenazine. 

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