Photochemische Synthese von Carbazolen und Indolo[3, 2‐b]carbazolen

Abstract

Zur Abgrenzung des präparativen Anwendungsbereiches der Carbazolsynthese durch Photocyclisierung von Di‐ und Triarylaminen wurde das photochemische Verhalten einiger substituierter Triarylamine 1, N, N′‐Diphenyl‐p‐phenylendiamine 2 und N, N′‐Diphenylbenzidine 3 untersucht. Während Fluor‐ und Methoxy‐substituierte Triphenylamine mit befriedigender Ausbeute in die entsprechenden Carbazole umgewandelt werden, sind Diarylaminobiphenyle und N, N′‐Diphenylbenzidin‐Derivate photochemisch stabil. N, N′‐Diphenyl‐N, N′‐dimethyl‐p‐phenylendiamin 3 a und N, N, N′, N′‐Tetraphenyl‐p‐phenylendiamin 3 b lassen sich hingegen zu den entsprechenden Indolo [3, 2‐b] carbazolen 5 a und 5 b umsetzen.

Isolation and Synthesis of Biologically Active Carbazole Alkaloids

“…[676][677][678] In 1975, Lamm et al claimed the synthesis of 5,11-dimethylindolo[3,2-b]carbazole by bidirectional photocyclization of N,N ′-dimethyl-N,N ′diphenyl-p-phenylenediamine. 48 However, this product was later reassigned as N,N ′-dimethylindolo[2,3-c]carbazole by the groups of Grellmann 664 and Chakrabarty. 679 Kistenmacher and Mu ¨llen reported a twostep synthesis of indolo[3,2-b]carbazole 960 from 1,4dibromo-2,5-dinitrobenzene 977.…”

“…Diphenylamines have been cyclized to carbazoles photochemically; − thermally in the presence of elemental iodine at 350 °C , or with platinum at 450−540 °C, via free radicals with benzoyl peroxide in chloroform; and chemically using activated metal catalysts such as degassed Raney nickel and palladium on charcoal . However, the yields are in most of the cases only low to moderate.…”

“…In 1963, Harley-Mason and Pavri reported another synthesis of indolo[3,2- b ]carbazole 960 by Fischer indolization of cyclohexane-1,4-dione bisphenylhydrazone . This method was also used by other groups for the synthesis of indolo[3,2- b ]carbazole 960 in different yields. − In 1975, Lamm et al claimed the synthesis of 5,11-dimethylindolo[3,2- b ]carbazole by bidirectional photocyclization of N , N ‘-dimethyl- N , N ‘-diphenyl- p -phenylenediamine . However, this product was later reassigned as N , N ‘-dimethylindolo[2,3- c ]carbazole by the groups of Grellmann 664 and Chakrabarty .…”

Synthesis of Linearly Fused Benzodipyrrole Based Organic Materials

“…Lamm et al performed the same reaction on the dimethylated precursor, which was closed photochemical to indolo[3,2- b ]carbazole in 10% yield. The electrochemical properties of this material were investigated [18,19]. Chakrabarty et al used a similar method, but they started from 3-aminocarbazole to perform one photochemical cyclization to obtain indolo[3,2- b ]carbazole [20].…”