Dehydrogenation of 6,7-dimethoxy-l-methyl-4-(N-methyl-pyrrolidin-2-yl)-3,4-dihydroisoquinoline (9) by Pd/C in tetraline leads to dehydrogenated products, rearrangement, and elimination of the pyrrolidine group mainly as N-methylpyrrolidine (Scheme 3).Abspaltung der Pyrrolidin-Gruppe bei der Dehydrierung eines 4-(~rrolidin-2-yl)-tetrahydroisochinolins Die Dehydrierung von 6.7-Dimethoxy-1 -methyl-4-(N-methyl-pyrrolidin-2-yl)-3,4-dihydroisochinolin (9) mit Pd/C in Tetralin fuhrt zu dehydrierten Produkten, zur Umlagerung und zur Abspaltung der Pyrrolidingruppe hauptsachlich als N-Methylpymlidin (Schema 3).The last step of our synthesis of rac. macrostomine comprises dehydrogenation of the pertinent 3,4-dihydroisoquinoline increment in 2 by Pd/C in tetraline at 205-210 'C. Under these conditions 2 is converted to rac. macrostomine (1) and mainly to the 1-berizylisoquinoline 31).Sharma and KapiP) prepared compound 2 by a different route. They quote that a "complex mixture" was obtained by Pd/C-dehydrogenation of 2, from which 1 was isolated in 20% yield, whilst Wykypiel and Seebach3) when dehydrogenating a 1,2-dibenzyl-4-(N-forylpyrrolidin-2-yl)-tetrahydroisoquinolin-4-ol observed elimination of the benzyl group from C-1 as a side reaction besides aromatization (note 13 in lit?)). In order to get some insight into the fate of the pyrrolidine increment the volatile components of the dehydrogenation of 2 to 1 were analyzed by GC-MS: we found N-methylpyrroline and traces of N-methylpyrrolidines).However, these compounds are hydrogenated and dehydrogenated under these conditions so that no clear-cut view of the cleavage mechanism could be obtained?Here we describe dehydrogenation of a 6,7-dimethoxy-1 -methyl-3,4-dihydroisoquinoline, substituted at C-4 with pyrrolidine or pyrroline increments (compounds 8 and 9). +) Dedicated to Prof. Fleischhacker, Wien, on the occasion of his 60th birthday. Synthesis2-( 3,4-Dimethoxyphenyl)-2-(N-methylpyrrol-2-yl)-ethylamine (4), prepared according to Kapil2) by enamine addition of N-methylpyrrol to the pertinent o-nitrostyrene and hydrogenation of the nitro-group to 4 over Raney-Ni, was converted to the acetamide 5. At this stage the pyrrol ring was hydrogenated to the corresponding 2,5-dihydro-derivative 6 by Zn/HCI/MeOH, which, in turn, was fully hydrogenated to 7 by Hfld/BaS04 in AcOEt. Bischler-Napieralski ring closure of the pyrroline 6 led to 8, that of 7 to the pyrrolidine-substituted 3,4-dihydroisoquinoline 9.
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.