Synthesis of Polycyclic Amines through Mild Metal‐Free Tandem Cross‐Dehydrogenative Coupling/Intramolecular Hydroarylation of N‐Aryltetrahydroisoquinolines and Crotonaldehyde

Abstract

A [4+2] cycloaddition reaction proceeding through tandem cross‐dehydrogenative coupling/intramolecular hydroarylation between N‐aryltetrahydroisoquinolines and crotonaldehyde was developed by virtue of enamine–iminium catalysis, which enabled the rapid construction of ring‐fused tetrahydroquinolines. The first metal‐free catalytic oxidative coupling of γ‐selective C(sp3)–H bonds of crotonaldehyde was realized by using a secondary amine catalyst and 2,3‐dichloro‐5,6‐dicyanoquinone.

Progress in the Chemistry of Tetrahydroquinolines

“…In related work, additional polycyclic systems derived from the dibenzo[af ]quinolizine framework and containing a tetrahydroquinoline subunit (compounds 867) were obtained via metal-free, amine-catalyzed oxidative cross-dehydrogenative coupling/intramolecular hydroarylation of N-aryltetrahydroisoquinolines 865 and crotonaldehyde 866 (Scheme 230). 388 After a detailed optimization study, the authors successfully employed catalyst 868, together with benzoic acid and DDQ, to afford the products in good yields and diastereoselectivities. The aldehyde function was subsequently reduced with sodium borohydride to afford the stable compounds 867 in good yields.…”

Light-Mediated Polymerization Induced by Semiconducting Nanomaterials: State-of-the-Art and Future Perspectives

“…Developing metal-free catalysts for chemical transformations has attracted numerous attention in the past few years because of their low toxicity and cost efficiency. ,,− Metal-free SNMs are mainly carbon-based materials with excellent photostability, low toxicity, and sustainable raw materials . Metal-free SNMs such as carbon QDs, , nanostructured conducting polymers, polymer nanofibers, and microsized carbon nitride particles have been developed for both controlled and free-radical polymerizations.…”

Metal-Free Synthesis of N-Aryl-Substituted Azacycles from Cyclic Ethers Using POCl3

“…8e It is obtained as a white solid (0.136 g, 65% yield); mp 45−47 °C; 1 H NMR (400 MHz, CDCl 3 ): δ 7.37−7.31 (m, 2H), 7.26−7.18 (m, 4H), 7.03 (d, J = 8.0 Hz, 2H), 6.89 (t, J = 7.6 Hz, 1H), 4.46 (s, 2H), 3.61 (t, J = 6.0 Hz, 2H), 3.03 (t, J = 5.6 Hz, 2H); 13 2-(3,5-Dimethylphenyl)-1,2,3,4-tetrahydroisoquinoline (5i). 24 It is obtained as a white solid (0.197 g, 83% yield); mp 49−51 °C; 1 H NMR (400 MHz, CDCl 3 ): δ 7.25−7.15 (m, 4H), 6.67 (s, 2H), 6.55 (s, 1H), 4.43 (s, 2H), 3.57 (t, J = 5.6 Hz, 2H), 3.02 (t, J = 6.0 Hz, 2H), 2.35 (s, 6H); 13 Phenylphosphoramidic Dichloride (6). 25 To a 20 mL vial containing a stirring mixture of aniline (1a) (0.093 g, 1.00 mmol) and DBU (0.304 g, 2.00 mmol) in xylene (3 mL) was added dropwise POCl 3 (0.230 g, 1.50 mmol) at room temperature.…”