Palladium-Catalyzed Preparation of N-Substituted Benz[c,d]indol-2-imines and N-Substituted Amino-1-naphthylamides

Transition-Metal-Free Synthesis of 2-Substituted Benzo[cd]Indoles via the Reaction of 1-Halo-8-lithionaphthalenes with Nitriles

A simple and effective organolithium approach to the synthesis of 2-substituted benzo[cd]indoles from peri-dihalonaphthalenes and nitriles has been developed. The reaction proceeds via a surprisingly easy intramolecular aromatic nucleophilic substitution facilitated by the "clothespin effect". The discovered transformation provides good isolated yields, allows usage of an extensive range of nitriles, and demonstrates a good substituents tolerance. UV-absorption and NMR spectra of the obtained benzo[cd]indoles and their protonated forms demonstrated exclusive protonation to the indole nitrogen atom even in the presence of two NMe2 groups in positions 5 and 6 (i. e. "proton sponge" moiety).

Palladium-Catalyzed Tandem C(sp3)-H Insertion Cyclization of 2-(2-Vinylarene)acetonitriles with Isocyanides to Access Naphthalen-2-amines

A Pd-catalyzed cyclization reaction of 2-(2-vinylarene)acetonitriles and isocyanides has been documented. Various naphthalen-2-amines were obtained in moderate to good yields under mild conditions. The in vitro cytotoxicity of all products was evaluated by MTT assay against seven human cancer cell lines. The results indicated that compounds 3ea, 3ma, and 3ob exhibited effective anticancer activities against the tested cancer cells.

Synthesis of Functionalized Tetrahydroquinoline Containing Indole Scaffold via Chemoselective Annulation of Aza-ortho-quinone Methide Precursor

The chemoselective annulation of aza-ortho-quinone methide generated by in situ o-chloromethyl sulfonamide has been achieved with bifunctional acyclic olefin. This efficient approach provides access to the diastereoselective synthesis of functionalized tetrahydroquinoline derivatives containing indole scaffolds through the inverse-electron-demand aza-Diels-Alder reaction under mild reaction conditions with excellent results (up to 93% yield, > 20:1 dr). Moreover, this article realized the cyclization of α-halogeno hydrazone with electron-deficient alkene affording the tetrahydropyridazine derivatives, which had never been reported.

Synthesis of sulfur-containing benzo[b]pyrrolo[2,1-c][1,4]oxazine-3,9-diones: blue light promoted radical cyclization process

The selective and controllable construction of spio-tricyclic skeletons through visible light promoted radical cyclization still remains challenging. Herein, a general and convenient protocol for the blue light-promoted radical-mediated cascade spiro-cyclization/Michael addition of N-arylpropiolamides with thiophenols under metal-free conditions was developed. In this protocol, commercially available hydrochloric acid was employed as the cheap promoter and air as the sustainable oxidant. In addition, many functional groups tolerate the reaction conditions and produce a series of sulfur-containing benzo[b]pyrrolo[2,1-c][1,4]oxazine-3,9-diones.

Regioselective intramolecular cyclization of o-alkynyl arylamines with the in situ formation of ArXCl to construct poly-functionalized 3-selenylindoles

In this article, a practical and metal-free method for the synthesis of poly-functionalized 3-selenyl/sulfenyl/telluriumindoles from o-alkynyl arylamines has been achieved. In this protocol, the in situ formation of selenenyl chloride, sulfenyl chloride or tellurenyl chloride is considered as the key intermediate and the 3-selenyl/sulfenyl/telluriumindoles can be obtained in good to excellent yields. Furthermore, the product 2-phenyl-3-(phenylselanyl)-1-tosyl-1H-indole can be selectively oxidized to compounds 2-phenyl-3-(phenylseleninyl)-1-tosyl-1H-indole and 2-phenyl-3-(phenylselenonyl)-1-tosyl-1H-indole in good yields.

Copper-catalyzed construction of (Z)-benzo[cd]indoles: stereoselective intramolecular trans-addition and SN-Ar reaction

Substituted benzo[cd]indoles are one of the most attractive frameworks because of their wide range of biological and optical activities. Herein, a copper-catalyzed one-step synthesis of biologically important polysubstituted benzo[cd]indoles starting from 8-alkynyl-1-naphthylamine derivatives is reported. In this protocol, many substituents tolerated the reaction conditions and produced (Z)-benzo[cd]indoles in good yields. Preliminary mechanistic studies indicated that the reaction proceeds via a stereoselective intramolecular trans-addition and S_N-Ar reaction with high selectivity and high yields. The synthesized polysubstituted (Z)-benzo[cd]indoles possess sulfonamide building blocks, which make them candidates for bioactive molecules.