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Introduction of adjacent oxygen-functionalities in Dimethyl Heptalenedicarboxylates


Rogano, F; Stojnic, D; Linden, A; Abou-Hadeed, K; Hansen, H J (2011). Introduction of adjacent oxygen-functionalities in Dimethyl Heptalenedicarboxylates. Helvetica Chimica Acta, 94(7):1194-1215.

Abstract

The bromination of dimethyl 8-methoxy-1,6,10-trimethylheptalene-4,5-dicarboxylate (6; Scheme 2) with N-bromosuccinimide (NBS) in N,N-dimethylformamide (DMF) leads in acceptable yields to the corresponding 9-bromoheptalenedicarboxylate 10 (Table 1). Ether cleavage of 6 with chlorotrimethylsilane (Me3SiCl)/NaI results in the formation of oxoheptalenedicarboxylate 13 in good yield (Scheme 4). The latter can be acetyloxylated to the (acetyloxy)oxoheptalenedicarboxylate 14 with Pb(OAc)4 in benzene (Scheme 5). Oxo derivative 14, in turn, can be selectively O-methylated with dimethyl sulfate (DMS) in acetone to the (acetyloxy)methoxyheptalenedicarboxylates 15 and 15′ (Scheme 6). The AcO group of the latter can be transformed into a benzyl or methyl ether group by treatment with MeONa in DMF, followed by the addition of benzyl bromide or methyl iodide (cf. Scheme 9). Reduction of the ester groups of dimethyl 7,8-dimethoxy-5,6,10-trimethylheptalene-1,2-dicarboxylate (25′) with diisobutylaluminium hydride (DIBAH) in tetrahydrofuran (THF) leads to the formation of the corresponding dimethanol 26′, which can be cyclized oxidatively (IBX, dimethyl sulfoxide) to 8,9-dimethoxy-6,7,11-trimethylheptaleno[1,2-c]furan (27; Scheme 11).

Abstract

The bromination of dimethyl 8-methoxy-1,6,10-trimethylheptalene-4,5-dicarboxylate (6; Scheme 2) with N-bromosuccinimide (NBS) in N,N-dimethylformamide (DMF) leads in acceptable yields to the corresponding 9-bromoheptalenedicarboxylate 10 (Table 1). Ether cleavage of 6 with chlorotrimethylsilane (Me3SiCl)/NaI results in the formation of oxoheptalenedicarboxylate 13 in good yield (Scheme 4). The latter can be acetyloxylated to the (acetyloxy)oxoheptalenedicarboxylate 14 with Pb(OAc)4 in benzene (Scheme 5). Oxo derivative 14, in turn, can be selectively O-methylated with dimethyl sulfate (DMS) in acetone to the (acetyloxy)methoxyheptalenedicarboxylates 15 and 15′ (Scheme 6). The AcO group of the latter can be transformed into a benzyl or methyl ether group by treatment with MeONa in DMF, followed by the addition of benzyl bromide or methyl iodide (cf. Scheme 9). Reduction of the ester groups of dimethyl 7,8-dimethoxy-5,6,10-trimethylheptalene-1,2-dicarboxylate (25′) with diisobutylaluminium hydride (DIBAH) in tetrahydrofuran (THF) leads to the formation of the corresponding dimethanol 26′, which can be cyclized oxidatively (IBX, dimethyl sulfoxide) to 8,9-dimethoxy-6,7,11-trimethylheptaleno[1,2-c]furan (27; Scheme 11).

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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:2011
Deposited On:07 Dec 2011 12:50
Last Modified:05 Apr 2016 15:08
Publisher:Verlag Helvetica Chimica Acta
ISSN:0018-019X
Publisher DOI:https://doi.org/10.1002/hlca.201100150

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