5599-70-2Relevant articles and documents
Carbazolyl nitrenium ion: Electron configuration and antiaromaticity assessed by laser flash photolysis, trapping rate constants, product analysis, and computational studies
Winter, Arthur H.,Gibson, Harry H.,Falvey, Daniel E.
, p. 8186 - 8195 (2008/02/13)
(Graph Presented) Laser flash photolysis of 1-(carbazol-9-yl)-2,4,6- trimethylpyridinium tetrafluoroborate generates the carbazolyl nitrenium ion (τ = 333 ns, kobs = 3.0 × 106 M -1S-1) having absorption bands at 570 and 620 nm in CH3CN. The nitrenium ion is found to have reactivity comparable to structurally similar closed-shell diarylnitrenium ions, but spectroscopic evidence favors an open-shell singlet diradical assignment for the observed nitrenium ion. The carbazolyl nitrenium ion is also more reactive than diarylnitrenium ions as a likely result of antiaromatic character. Ab initio and hybrid DFT calculations were performed to address the degree of antiaromaticity in this and similar nitrenium ions through analysis of optimized geometries, nucleus independent chemical shifts, and isodesmic reactions.
On the Synthesis and Isolation of Chlorocarbazoles Obtained by Chlorination of Carbazoles
Bonesi, Sergio M.,Erra-Balsells, Rosa
, p. 877 - 889 (2007/10/03)
Carbazole (1) undergoes electrophilic aromatic substitution with various chlorinating reagents. Although 3-chlorocarbazole (1b), 3,6-dichlorocarbazole (1d) and 1,3,6,8-tetrachlorocarbazole (1f) obtained by chlorination of carbazole were isolated and characterized sometime ago, 1-chlorocarbazole (1a), 1,6-dichlorocarbazole (1c) and 1,3,6-trichlorocarbazole (1e) had never been isolated from the reaction mixtures. The preparation and subsequent isolation and characterization of 1a, 1b, 1e, 1d, 1e and 1f are reported (mp, tF, Rf, 1H- and 13C-nmr, ms). Physical and spectroscopic properties of le are compared with those of 1b and 1d in order to show that the former is the major product obtained in several chlorinating processes. As chlorinating reagents, chlorine in glacial acetic acid, sulfuryl chloride, N-chlorosuccinimide, N-chlorosuccinimide-silica gel, N-chlorobenzotriazole, and N-chlorobenzotriazole-silica gel in dichloromethane and in chloroform have been used and their uses have been compared. The chlorination reaction of different carbazole derivatives such as 2-hydroxycarbazole (2), 2-acetoxycarbazole (3), 3-bromocarbazole (4) and 3-nitrocarbazole (5) was also studied and the corresponding chloro derivatives 2a, 2b, 2c, 2d, 3a, 3b, 3c, 3d, 3e, 3f, 4a, 4b, 4c, 4d, 5a and 5b are described for the first time. Semiempirical PM3 calculations have been performed in order to predict reactivity of carbazole (1), substituted carbazoles 2-5 and chlorocarbazoles (Scheme 1). Theoretical and experimental results are discussed briefly.
Acid-Catalyzed Intermolecular Rearrangement of N-Chlorocarbazole
Rosa, Michael De,Quesada, Andres P.,Dodsworth, David J.
, p. 173 - 175 (2007/10/02)
The chlorination of carbazole with sodium hypochlorite in CH2Cl2, CHCl3, or CCl4 gave N-chlorocarbazole in 63-95percent yield.It rearranged in refluxing methanol to give carbazole, 3-chlorocarbazole, 1-chlorocarbazole, 3,6-dichlorocarbazole, and 1,6-dichlorocarbazole.These chlorocarbazoles were formed in an acid-catalyzed intermolecular reaction.In the presence of potassium carbonate dechlorination of N-chlorocarbazole was observed.No evidence for an intramolecular rearrangement was found.
