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A new alkylation method for heptalene-4,5-dicarboxylates and of one of their pseudoester forms


Abou-Hadeed, Khaled; Molnar, Zoltàn A; Göksaltık, Pinar; Kunz, Roland W; Linden, Anthony; Hansen, Hans-Jürgen (2012). A new alkylation method for heptalene-4,5-dicarboxylates and of one of their pseudoester forms. Helvetica Chimica Acta, 95(6):885-921.

Abstract

Dimethyl heptalene-4,5-dicarboxylates† undergo preferentially a Michael addition reaction at C(3) with α-lithiated alkyl phenyl sulfones at temperatures below −50°, leading to corresponding cis-configured 3,4-dihydroheptalene-4,5-dicarboxylates (cf. Table 1, Schemes 3 and 4). The corresponding heptalenofuran-1-one-type pseudoesters of dimethyl heptalene-4,5-dicarboxylates (Scheme 5) react with [(phenylsulfonyl)methyl]lithium almost exclusively at C(1) of the furanone group (Scheme 6). In contrast to this expected behavior, the uptake of 1-[phenylsulfonyl)ethyl]lithium occurs at C(5) of the heptalenofuran-1-ones as long as they carry a Me group at C(11) (Schemes 6 and 7). The 1,4- as well as the 1,6-addition products eliminate, on treatment with MeONa/MeOH in THF, benzenesulfinate, thus leading to 3- and 4-alkylated dimethyl heptalene-4,5-dicarboxylates, respectively (Schemes 8–13). The configuration of the addition reaction of the nucleophiles to the inherently chiral heptalenes is discussed in detail (cf. Schemes 14–19) on the basis of a number of X-ray crystal-structure determinations as well as by studies of the temperature-dependence of the 1H-NMR spectra of the addition products.

Dimethyl heptalene-4,5-dicarboxylates† undergo preferentially a Michael addition reaction at C(3) with α-lithiated alkyl phenyl sulfones at temperatures below −50°, leading to corresponding cis-configured 3,4-dihydroheptalene-4,5-dicarboxylates (cf. Table 1, Schemes 3 and 4). The corresponding heptalenofuran-1-one-type pseudoesters of dimethyl heptalene-4,5-dicarboxylates (Scheme 5) react with [(phenylsulfonyl)methyl]lithium almost exclusively at C(1) of the furanone group (Scheme 6). In contrast to this expected behavior, the uptake of 1-[phenylsulfonyl)ethyl]lithium occurs at C(5) of the heptalenofuran-1-ones as long as they carry a Me group at C(11) (Schemes 6 and 7). The 1,4- as well as the 1,6-addition products eliminate, on treatment with MeONa/MeOH in THF, benzenesulfinate, thus leading to 3- and 4-alkylated dimethyl heptalene-4,5-dicarboxylates, respectively (Schemes 8–13). The configuration of the addition reaction of the nucleophiles to the inherently chiral heptalenes is discussed in detail (cf. Schemes 14–19) on the basis of a number of X-ray crystal-structure determinations as well as by studies of the temperature-dependence of the 1H-NMR spectra of the addition products.

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Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Chemistry
Dewey Decimal Classification:540 Chemistry
Language:English
Date:2012
Deposited On:11 Dec 2012 16:48
Last Modified:05 Apr 2016 16:10
Publisher:Wiley-Blackwell
Series Name:Helvetica Chimica Acta
ISSN:0018-019X
Funders:Swiss National Science Foundation
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.1002/hlca.201100510
Permanent URL: https://doi.org/10.5167/uzh-68066

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