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New Routes to Fused Isoquinolines


Awad, Enas M; Elwan, Nehal M; Hassaneen, Hamdi M; Linden, Anthony; Heimgartner, Heinz (2002). New Routes to Fused Isoquinolines. Helvetica Chimica Acta, 85:320-332.

Abstract

Treatment of 6,7-diethoxy-3,4-dihydroisoquinoline (8) and its 1-methyl derivative 12 with hydrazonoyl halides 10 in the presence of Et3N in THF under reflux afforded the corresponding 5,6-dihydro-1,2,4-triazolo[3,4-a]isoquinolines 11 and 13, respectively, in high yield (Schemes 2 and 3). The products are formed via regioselective 1,3-dipolar cycloaddition of the intermediate nitrilimines 9 with the isoquinoline C=N bond. Reaction of 6,7-diethoxy-3,4-dihydroisoquinoline-1-acetonitrile (4a) with ethyl alpha-cyanocinnamates 15 in the presence of piperidine in refluxing MeCN yielded benzo[a]quinolizin-4-ones 16 (Scheme 4). Under the same conditions, 12 and arylidene malononitriles 19 reacted to give benzo[a]quinolizin-4-imines 20 (Scheme 5). Instead of 15 and 19, mixtures of an aromatic aldehyde, and ethyl cyanoacetate or malononitrile, respectively, can be used in a one-pot reaction.

Abstract

Treatment of 6,7-diethoxy-3,4-dihydroisoquinoline (8) and its 1-methyl derivative 12 with hydrazonoyl halides 10 in the presence of Et3N in THF under reflux afforded the corresponding 5,6-dihydro-1,2,4-triazolo[3,4-a]isoquinolines 11 and 13, respectively, in high yield (Schemes 2 and 3). The products are formed via regioselective 1,3-dipolar cycloaddition of the intermediate nitrilimines 9 with the isoquinoline C=N bond. Reaction of 6,7-diethoxy-3,4-dihydroisoquinoline-1-acetonitrile (4a) with ethyl alpha-cyanocinnamates 15 in the presence of piperidine in refluxing MeCN yielded benzo[a]quinolizin-4-ones 16 (Scheme 4). Under the same conditions, 12 and arylidene malononitriles 19 reacted to give benzo[a]quinolizin-4-imines 20 (Scheme 5). Instead of 15 and 19, mixtures of an aromatic aldehyde, and ethyl cyanoacetate or malononitrile, respectively, can be used in a one-pot reaction.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Chemistry
Dewey Decimal Classification:540 Chemistry
Language:English
Date:2002
Deposited On:03 Oct 2013 14:03
Last Modified:07 Dec 2017 22:41
Publisher:Wiley-Blackwell
ISSN:0018-019X
Funders:Swiss Federal Government (National Scholarship for Foreign Students)
Publisher DOI:https://doi.org/10.1002/1522-2675(200201)85:1<320::AID-HLCA320>3.0.CO;2-X

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