Convenient One-Step Synthesis of Benzo[c]phenanthridines by Three-Component Reactions of Isochromenylium Tetrafluoroborates and Stilbenes in Acetonitrile

Chemo-selective control of Ritter-type reaction by coordinatively unsaturated inorganic salt hydrates

We used a readily available water source, MgSO4·2H2O, to realize the control of the chemo-selectivity of the Ritter-type reaction efficiently.

The serendipitous effect of KF in Ritter reaction: Photo-induced amino-alkylation of alkenes

Ritter reaction has been recognized as an elegant strategy to construct the C−N bond. Its key feature is forming the carbocation for nucleophilic attack by nitriles. Herein, we report a complementary visible-light-induced three-component Ritter reaction of alkenes, nitriles, and α-bromo nitriles/esters, thereby providing mild and rapid access to various γ-amino nitriles/acids. Mechanistic studies indicated that traceless fluoride relay, transforming KF into imidoyl fluoride intermediate, is critical for the efficient reaction switch from atom transfer radical addition (ATRA) to the Ritter reaction. This approach to amino-alkylation of alkenes is chemoselective and operationally simple.

•

Using light irradiation to promote amino-alkylation of alkenes

•

Using KF to facilitate three-component Ritter reaction

•

Access functionalized amides under mild conditions

Recent advances of Ritter reaction and its synthetic applications

This review provides a comprehensive survey of Ritter reactions from 2014 to 2020.

Synthesis of 11,12-dihydro benzo[c]phenanthridines via a Pd-catalyzed unusual construction of isocoumarin ring/FeCl3-mediated intramolecular arene-allyl cyclization: First identification of a benzo[c]phenanthridine based PDE4 inhibitor

In spite of their various pharmacological properties the anti-inflammatory potential of benzo[c]phenanthridines remained underexplored. Thus, for the first time PDE4 inhibitory potential of 11,12-dihydro benzo[c]phenanthridine/benzo[c]phenanthridine was assessed in vitro. Elegant synthesis of these compounds was performed via a multi-step sequence consisting of a Pd-catalyzed unusual construction of 4-allyl isocoumarin ring and FeCl₃-mediated intramolecular regio- as well as site-selective arene-allyl cyclization as key steps. The overall strategy involved Sonogashira coupling followed by isocoumarin and isoquinolone synthesis, then chlorination and subsequent cyclization to afford a range of 11,12-dihydro derivatives. One of these dihydro compounds was converted to the corresponding benzo[c]phenanthridine that showed concentration dependent inhibition of PDE4B affording an initial hit molecule. The SAR study suggested that 11,12-dihydro analogs were less potent than the compound having unsaturation at the same part of the ring.

o-Iodoxybenzoic acid mediated generation of aryl free radicals: synthesis of stilbenes through C–C cross-coupling with β-nitrostyrenes

The generation of an aryl free radicals in the presence of nitrostyrenes through a combination of aryl hydrazines and o-iodoxybenzoic acid led to the synthesis of stilbenes by forming a new carbon–carbon bond after subsequent elimination of a nitrosyl radical.

A copper-catalyzed Ritter-type cascade via iminoketene for the synthesis of quinazolin-4(3H)-ones and diazocines

We have developed a copper-catalyzed Ritter-type reaction/cyclization cascade of anthranilic acids and nitriles, affording the quinazolin-4(3H)-ones and diazocines.