16261-32-8Relevant academic research and scientific papers
Synthesis of Tetrahydroisoquinolines by Visible-Light-Mediated 6- exo -trig Cyclization of α-Aminoalkyl Radicals
Bach, Thorsten,Grübel, Michael,Jandl, Christian
, p. 1825 - 1829 (2019)
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 molpercent 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 (41-83percent). 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.
