Carbazoles lithiation

Carbazoles, halogenation, 59, 266-8 Carbazole, lithiation, 56, 182 Carbazoles, 9-alkyl-, lithiation, 56, 182,... 

Competitive metallation experiments with IV-methylpyrrole and thiophene and with IV-methylindole and benzo[6]thiophene indicate that the sulfur-containing heterocycles react more rapidly with H-butyllithium in ether. The comparative reactivity of thiophene and furan with butyllithium depends on the metallation conditions. In hexane, furan reacts more rapidly than thiophene but in ether, in the presence of tetramethylethylenediamine (TMEDA), the order of reactivity is reversed (77JCS(P1)887). Competitive metallation experiments have established that dibenzofuran is more easily lithiated than dibenzothiophene, which in turn is more easily lithiated than A-ethylcarbazole. These compounds lose the proton bound to carbon 4 in dibenzofuran and dibenzothiophene and the equivalent proton (bound to carbon 1) in the carbazole (64JOM(2)304). 

D. Pyrroles, Indoles. Carbazoles, and Pyrazoles Lithiation in an Al-Phenyl... 

In further contrast to carbazole itself, benzo[a]carbazole readily undergoes direct lithiation without the need for a protecting group, with metala-tion occurring at the y-position to give the 1,11-dilithio species (Scheme... 

A similar approach was used in grafting Cjq onto a pregenerated lithiated polyethylene surface [121]. A polyethylene film with terminal diphenylmethyl groups was deprotonated with BuLi to yield an anionic polyethylene surface that was treated with Cg0 and quenched with methanol. The incorporation at the polyethylene surface was determined by XPS, UV/Vis and fluorescence spectroscopy. This reaction also works for polyisopropene, polybutadiene [69], poly(vinylbenzyl chloride) or poly(N-vinylcarbazole) PVK [54] with BuLi or NaH as a base. Charge-transfer interactions in the soluble fullerene-PVK derivative between the positively charged carbazole and Cjq lead to an enhanced photoconductivity compared with PVK [54]. 

Carboxylation of carbazol-9-ylpotassium gave a moderate yield of the 3-carboxylic acid. The Kolbe-Schmidt carboxylation of 2-hydroxycarba-zole gave the 1-acid (50%) and the 3-acid as a minor product (12%). " Lithiation ° of 9-methyl- or 9-ethylcarbazole and carboxylation gave the 1-carboxylic acids. 

Carbazoles, 9-phenyl-, lithiation, 56, 191 Carbazole, 9-propargyl-, reaction with TeCU, 58, 112... 

Diazotization, of 6-amino-2,3-dihydro-1,4-diazepinium salt, 56, 33 Dibenz[c,e][ 1,2]azaborine, 5,6-dihydro-, chlorination, bromination, 59, 309 Dibenz[i/]azepine, and 10,11-dihydro-, lithiation, 56, 273 Dibenziodole( + 1) ions, 56, 338 Dibenzo[fl,c]carbazole, 7-methoxymethyl-, lithiation, 56, 183... 

An interesting approach to carbazoles has been devised, wherein for instance the diarylamine 224 underwent lithiation initially generating the benzyne 225, which provided the final product 226 after ring closure to 227 followed by introduction of a suitable electrophile (Scheme 26) <2006JOC6291>. 

Imidazolidines may also act as ortho directing groups the lithiadon of l,3-dimethyl-2-phenylimidazo-lidine followed by addition to benzophenone proceeds in 63% yield. Carbazole aminals can be metal-ated ortho to the nitrogen, while benzo[a]carbazole may be dili iated at nitrogen and the 1-position. A 2-amino group of a biphenyl directs lithiation to the 2 -position of the other ring in a novel synthesis of a phenanthride. ... 

The main product of the reaction of the biphenyl derivative (143) with triethyl phosphite is 9-ethyl-4,5-dimethylcarbazole (144). Treatment of the diamine (145) with phosphoric acid yields a mixture of carbazole and 2-t-butylcarbazole. Di-lithiation of the o-bromoaniline derivative (146), followed by addition of 2-chlorocyclohexanone, affords the hexahydro-carbazole (147). ... 

The iV-(pyrrolidinomethyl) derivative of carhazole is lithiated at Cl using either r-hutyllithiiun or n-butyllithium/TMEDA. Good yields of 1-substituted carbazole can be obtained with the usual electrophiles <88JOC794>. 

The intramolecular trapping of benzyne intermediates with tethered nucleophiles is a powerful strategy for the synthesis of benzo-fused heterocycles. In this field, 7-functionalized benzoxazoles 59 and benzothiazoles 60 have been prepared by anionic cyclization of the corresponding lithiated benzyne (thio)amides and (thio)carbamates, which were generated from 3-haloaniline derivatives (Scheme 12.34) [55]. Related to this, substituted indolines 61 have also been accessed by benzyne-mediated cyclization-functionalization from Boc-protected (2-bromo-4-methoxy)phenetylamines using Mg(TMP)2 2LiCl as a base. This methodology has also been applied to the preparation of functionalized carbazoles (Scheme 12.34) [56]. 

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