Modular Synthesis of Polysubstituted Quinolin-3-amines by Oxidative Cyclization of 2-(2-Isocyanophenyl)acetonitriles with Organoboron Reagents

Abstract

Polysubstituted quinolin-3-amines are vital structural motifs because of their broad biological activities as well as versatile transformational abilities. However, they are not easily accessible. We disclose a protocol with Mn­(III) acetate as a mild one-electron oxidant promoting a radical process to construct polysubstituted quinolin-3-amines. 2-(2-Isocyanophenyl)­acetonitriles and organoboron reagents are suitable substrates for this reaction. The remarkable advantages of this protocol are the practical method, mild approach, high reaction efficiency, and good compatibility of functional groups, providing straightforward access to functional quinoline derivatives.

Advances in free-radical alkylation and arylation with organoboronic acids

“…40 In 2018, Wu and co-workers discovered a novel synthesis of 2-substituted benzothiazoles via radical addition/cyclization of organoboronic acids to 2-isocyanoaryl thioethers (Scheme 15d). 41 Furthermore, several interesting radical cascade cyclization reactions of isocyano-nitriles with boronic acids have been developed by Wang and Ji, 42 Song, 43 Li and Wang et al 44 (Scheme 15e–g). Finally, Yu and coworkers reported a Mn( iii )-mediated radical cyclization of ortho -vinyl arylisocyanides with arylboronic acids giving rise to an array of 2-aryl quinolines (Scheme 15h).…”

Mn(iii)-Catalyzed cascade cyclization reaction ofo-acyl aromatic isocyanides with boronic acids

“…4 In particular, Chatani and co-workers reported a novel Mn( iii )-mediated cascade cyclization reaction of 2-isocyanobiaryls with arylboronic acids via a homolytic aromatic substitution. 5 Subsequently, significant progress in Mn salt-mediated systems has been made in the reported studies of Alabugin, 6 Wu, 7 Ji, 8 Zhu, 9 Yu, 10 Begum, 11 Song 12 and our previous work. 13 Overall, these transformations typically required a radical cyclization process in the presence of stoichiometric amounts of Mn salts.…”

Visible light-enabled alkylation of enol acetates with alkylboronic acids for the synthesis of α-alkyl ketones

“…18 In contrast, commercially abundant and easily available alkylboronic acids were hardly used as alkylation reagents in those reactions. 19 Herein, by combining the effects of a photocatalyst and an oxidant, we also developed the photocatalytic alkylation of enol acetate and alkylboronic acid under mild conditions, and the corresponding α-alkyl ketones were obtained in moderate to good yields.…”