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DOI: 10.1055/s-0039-1690006
Synthesis of Tetrahydroisoquinolines by Visible-Light-Mediated 6-exo-trig Cyclization of α-Aminoalkyl Radicals
Publikationsverlauf
Received: 14. Mai 2019
Accepted after revision: 01. Juli 2019
Publikationsdatum:
17. Juli 2019 (online)


Abstract
Starting from the respective tertiary α-silylmethyl amines, the intramolecular cyclization of α-aminoalkyl radicals to Michael acceptors produced tetrahydroisoquinolines. The reaction conditions included the use of 5 mol% of an iridium photoredox catalyst, dimethylformamide as the solvent, and equimolar amounts of water and cesium carbonate as the additives. 13 substrates were synthesized from ortho-alkylbenzaldehydes in a three-step procedure involving a carbonyl condensation, a radical bromination, and a substitution by a secondary α-silylmethyl amine. After optimization of the photocyclization, the reaction delivered tetrahydroisoquinolines in moderate to high yields (41–83%). A facial diastereoselectivity (dr ≅ 80:20) was observed with chiral substrates and a crystal structure provided evidence for the relative configuration of the major diastereoisomer. A catalytic cycle with direct electron transfer to the photoexcited metal catalyst is proposed.
Supporting Information
- Supporting information for this article is available online at https://doi.org/10.1055/s-0039-1690006.
- Supporting Information
Primary Data
- for this article are available online at https://doi.org/10.1055/s-0039-1690006 and can be cited using the following DOI: 10.4125/pd0105th.
- Primary Data