Selektive katalytische Hydrierungen und Hydrogenolysen, 5. Mitt. Ein einfacher Zugang zu 1‐Benzyl‐5,6,7,8‐tetrahydroisochinolinen

Abstract

Die 1-Benzylisochinoline 1 lassen sich mit Pt-und Ru-Katalysatoren selektiv zu den Titelverbindungen 2 hydrieren; mit Pd-Kohle entstehen auflerdem ca. 5 % der Isomere 3, die uber die N-Acetylderivate, beispielsweise 7d, abgetrennt werden konnen. -Bei langen Hydrierzeiten wird mit Platin nur der unsubstituierte -, bei hoheren Temperaturen auch der substituierte Benzylrest unter gleichzeitiger C,O-Hydrogenolyse mithydriert (s. la-4 bzw. ld-4). -Die Struktur der Verbindungen 2 wird u. a. durch 'H-NMR-Spektroskopie, die von 2azusatzlich durch Synthese aus 2e uber S+ 6 bewiesen. Selective Catalytic Hydrogenations and Hydfogenolyses, V*): Convenient Preparation of 1-Beozyl-5,6,7,8-tehhydroisoquinolines1-Benzylisoquinolines 1 can be hydrogenated selectively with Pt and Ru catalysts to yield the title compounds 2. Using Pdlcharcoal, the products 2 contain ca. 5 % of the isomers 3, which can be separated via the N-acetyl derivatives, e. g. 7d. Extended reaction times in the presence of platinum cause simultaneous hydrogenation of the unsubstituted aromatic nucleus of the benzyl group. At higher temperatures, the substituted benzyl nucleus is hydrogenated, too, involving C,Ohydrogenolysis, e. g. la-, 4 or Id+ 4. The structures of 2 were proved by 'H-NMR spectroscopy. Compound 2a was prepared independently from 2c via 5+ 6. R3 R4Q(1 R2 1 1 3 1 -2 Pd/Eioesslg + 3 bar/60°C H2 -90% -5 ?a !?365-6233/85-559 $02.50/0 OVCH Verlagsgesellschafi mbH, D-6940 Weinheim, 1985

A Short Approach to N-Aryl-1,2,3,4-tetrahydroisoquinolines from N-(2-Bromobenzyl)anilines via a Reductive Amination/Palladium-Catalyzed Ethoxyvinylation/Reductive N-Alkylation Sequence

“…2e Further, N-aryl-1,2,3,4-tetrahydroisoquinolines have been described as ligands for estrogen receptors, 3a Gprotein coupled receptors, 3b and serotonin transporters. 3c Whereas common 1-substituted 1,2,3,4-tetrahydroisoquinolines are readily available starting from arylethylamines through established cyclization reactions (Pictet-Spengler, Bischler-Napieralski, followed by reduction) 4 or through controlled reduction of fully aromatic isoquinolines, 5 to date, there are only a limited number of published synthetic routes to N-aryl-1,2,3,4-tetrahydroisoquinolines. These include mainly N-arylations of 1,2,3,4-tetrahydroisoquinolines utilizing aryl bromides or iodides under palladium (Buchwald-Hartwig reaction) 6a,b or copper catalysis (Ullmann reaction); 6c alternatively, arylboronic acids or trifluoroborates were coupled under copper catalysis.…”