Carbazoles carbazole nitrogen atoms

Another example of functionalization of carbazole nitrogen atoms was exhibited when Baran and co-workers demonstrated that carbazole and derivatives thereof were dimerized under electrochemical conditions. The aforementioned methodology enabled the concise and first synthesis of an N-N linked natural product—dixiamycin B (287) (14JA5571). 

Carbazole is a weak acid and will form salts with strong bases by loss of the iV-hydrogen. These salts provide the usual means for the introduction of substituents onto the nitrogen atom (see Section II,B). The pK of carbazole is 17.1 (extrapolated value in water) or 19.9 in dimethyl sulfoxide. This... 

With few exceptions, the reactions of functional groups separated by a chain of two or more saturated atoms from carbazole nitrogen show no deviation from their normal behavior. 

Pyrroles, indoles, isoindoles and carbazoles having no substituent at the nitrogen atom are weakly acidic and, upon treatment with a strong base, form anions which are capable of subsequent reaction with electrophiles at the nitrogen atom and/or the 1-position of isoindoles, the 2-position of pyrroles and the 3-position of indoles. 1-Substituted pyrroles and indoles also react with butyllithium to give 1-substituted 2-pyrrolyl and 2-indolyl anions (see Section 3.05.1.2.9). 

Carbazole (CBZ) (9) has an ionizable proton at the nitrogen atom whose ESPT properties have been studied in detail. It has a pKa value of 21.1 and a pK value of 11.0 [128], Its absorption maximum is at 325 nm, with a moderately high extinction coefficient of 4200 M 1 /cm. The P form (9) and the DP form (10) emit at 362 and 417 nm, respectively. The fluorescence quantum yield in nonpolar medium is 0.41 [129], All these make it a possible ESPT probe for microhetero-geneous media, the Ap/f, suggesting a possible use in alkaline pH ranges. 

The styryl dyes also include compounds in which the amino aryl nitrogen atom is part of a carbazole (as in the commercial dye 30) [71], phenoxazine [72], or tet-rahydrobenzoxazine system [73],... 

Polycyclic aromatic nitrogen compounds, such as quinoline, indole, acridine, and carbazole, are the main nitrogen-containing compounds in oil fractions, and monocyclic pyridine and pyrrole as well as anilines are present in coal tar (Scheme 11). Saturated cyclic amines are found as products of ring hydrogenation of the compounds shown in Scheme 11 after HDN. Aliphatic amines are rarely found in fuels and only in low concentrations after HDN since their nitrogen atoms are easily removed. 

Benzoindole 114 has been synthesized by a remarkable sequence, in which the benzannulation precursor 113 is pre-assembled starting from two different chromium carbenes. It is formed in a [3+2] cycloaddition, in which the acylamino carbene complex 111 acts as the dipolar component and the alkynylcarbene complex 112 serves as the dipolarophile. The resulting 3-pyrrolylcarbene complex 113 undergoes a photoinduced intramolecular benzannu-lation to give the benzoindole 114 [84a]. This strategy complements an approach towards carbazoles [84b], Isoindolines and 1,2,3,4-tetrahydroisoquinolines are accessible from the reaction of pentacarbonyl (a-methoxyethylidene) chromium with 7r,co-dialkynes bearing a nitrogen atom in the carbon ether [84c]. 

Uleine methiodide underwent a facile Hofmann degradation to give an optically inactive compound (CCXLVIII), which retained the two nitrogen atoms and had carbazole UV-absorption. A further Hofmann degradation eliminated Nb and gave a product (CCXLIX) with somewhat extended carbazole absorption, which underwent ready catalytic reduction with saturation of one double bond to give a substituted... 

The monomer 2-(N-carbazolyl)ethyl methacrylate (CzEMA) was first prepared by reacting 9H-carbazole-9-ethanol with methacryloyl chloride, using an excess of triethylamine, in dichloromethane at 0°C. The yields of reaction were not very high (typically 60%) due to the presence of the nitrogen atom on the monomer, which can trap a proton during the reaction. This protonated monomer is eliminated while making several aqueous washes to remove the excess of salts in the product. The purity of the final monomer was demonstrated by H-NMR (Fig. 6). 

The carbazole compounds, (77 -Af-carbazolyl)2Ca(pyridine)4, (Tj -N-car-bazolyl)2Sr(NH3)(DME)2, and (i7 -Af-carbazolyl)2Ba(DME)3 (Fig. 9), are colorless or yellow solids that have good solubility in donor solvents such as pyridine. They are monomeric in the solid state with the carbazolyl ligands bonded only through the nitrogen atom (tj ) to the metals. The metal coordination spheres are completed by incorporation of the Lewis bases pyridine, DME, and ammonia. A smooth increase in coordination number with metal size, from 6 (Ca) to 7 (Sr) to 8 (Ba), is observed in these compounds. The reason for the Tj -Af-bondingof the carbazolyl ligand instead of multihapto bonding as occurs in the alkali metal compounds of carbazole and the fluorenyl compounds of the alkaline-earth metals (see Section III,G,2) is presently unclear. ... 

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