Novel synthesis of benzo[b]carbazoles

A new method was adopted for the synthesis of benzo[b]carbazoles by Claisen condensation followed by Fischer indole cyclization. Newly synthesized benzo[b]carbazoles were treated with ethanol amine in the presence of polyphosphoric acid which leads to the formation of pyrazino carbazoles. All the synthesized compounds were characterized by all spectral means.     

Synthesis of Fischer indole derivatives using carboxyl-functionalized ionic liquid as an efficient and recyclable catalyst

Fischer indole cyclization of phenylhydrazine and various ketones using carboxyl-functionalized ionic liquid, 1-carboxymethyl-3-methylimidazolium tetrafluoroborate (abbreviated as [cmmim][BF4]) as catalyst was successfully performed. The yields of thetarget compounds were 80-92%, the purities were 96-98%. The catalyst could be rocovered and reused for at least six times without significant loss in activity.     

1,2,4-Triazines in Organic Synthesis. 9. Synthesis of 3-(3-Ethylindol-2-yl)-5,6,7,8-tetrahydroisoquinoline Using the Fischer Reaction under the Usual Conditions and with Microwave Irradiation

The nucleophilic substitution of hydrogen in 3-methylthio-1,2,4-triazine by the carbanions of nitrobutane and 4-nitrobut-1-ene gave oximes, the selective fission of which using sodium dithionite gave ketones in the case of compounds with a saturated carbon chain. Ketones in Diels-Alder reaction with 1-pyrrolidinocyclohex-1-ene gave 3-acyl-1-methylthio-5,6,7,8-tetrahydroisoquinolines. Phenylhydrazones of the compounds obtained underwent Fischer reaction under usual conditions and also when using microwave irradiation on a solid support. The final 3-(3-ethylindol-2-yl)-5,6,7,8-tetrahydroisoquinoline was obtained via reductive desulfuration using Raney nickel in ethanol.     

Novel Method for the Synthesis of 6,12‐Dihydro‐2‐Methylindolo[2,3‐ b]Carbazol‐6‐Ones

A novel method for the synthesis of 6,12‐dihydro‐2‐methylindolo[2,3‐b]carbazol‐6‐ones was developed from 1‐oxo‐2,3,4,9‐tetrahydro‐1H‐carbazol‐1‐one through methyl 6‐methyl‐2‐(1‐oxo‐2,3,4,9‐tetrahydro‐1H‐carbazol‐2‐yl)oxoacetate in good yields. This method provides an alternative path for the synthesis of this product using 2‐hydroxy methylene‐2,3,4,9‐tetrahydro‐1H‐carbazol‐1‐one.     

A Click Approach to Polymetallic Chromium(0) and Tungsten(0) Fischer‐Carbene Complexes and Their Use in the Synthesis of Functionalized Polymetallic Metal?Carbene Complexes

Alkynylamino Cr⁰ and W⁰ Fischer carbenes undergo a CuAAC reaction with a diverse range of di‐, tri‐, and tetra‐azides to produce polymetallic chromium(0) and tungsten(0) (Fischer)‐carbene complexes in good‐to‐excellent yields. This method is simple, versatile, and is suitable for the preparation of a diverse range of structures with a high level of symmetry. Moreover, the resulting polymetallic carbene complexes are suitable partners for the peripheral functionalization of the metal nuclei, whilst retaining the metal fragment. This fact has been demonstrated in a simultaneous Pauson–Khand reaction, which, in some cases, allows for the generation of four bicyclic [5,5] rings on the periphery of a tetrametallic molecule in a process that involves the formation of 12 new C? C bonds, with four simultaneous CO‐insertion processes. The electrochemistry of the polymetallic Fischer carbenes show completely independent behavior for each nucleus, as well as an anomalous observation of the reversible oxidation of the allyl substituents, which has not been reported before in this class of chemistry.     

PTC‐Promoted Japp–Klingmann Reaction for the Synthesis of Indole Derivatives

Abstract

Indole derivatives have been efficiently synthesized from ethyl 2‐phenylhydrazono‐5‐phthalimido‐pentanoate and its derivatives, which were obtained by Japp–Klingmann reaction under phase‐transfer catalytic (PTC) conditions. Several different phase‐transfer catalysts were investigated and dimethyldioctadecyl ammonium chloride (DMDOA) was found to promote this reaction efficiently. Using DMDOA as the PTC, aryl hydrazones were obtained in yields of 90%. The pure aryl hydrazones were then efficiently cyclized to indole derivatives in yields of more than 80%.