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A New Alkylation Method for Heptalene‐4,5‐dicarboxylates and of One of Their Pseudoester Forms
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Titel: |
A New Alkylation Method for Heptalene‐4,5‐dicarboxylates and of One of Their Pseudoester Forms |
In: | Helvetica Chimica Acta, 95, 2012, 6, S. 885-921 |
veröffentlicht: |
Wiley
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Umfang: | 885-921 |
ISSN: |
1522-2675 0018-019X |
DOI: | 10.1002/hlca.201100510 |
Zusammenfassung: | <jats:title>Abstract</jats:title><jats:p>Dimethyl heptalene‐4,5‐dicarboxylates<jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="#fnppp" /><jats:fn><jats:p>The locants of heptalene itself are maintained throughout the whole work. See footnote 4 in [1] for reasoning.</jats:p></jats:fn> undergo preferentially a <jats:italic>Michael</jats:italic> addition reaction at C(3) with <jats:italic>α</jats:italic>‐lithiated alkyl phenyl sulfones at temperatures below −50°, leading to corresponding <jats:italic>cis</jats:italic>‐configured 3,4‐dihydroheptalene‐4,5‐dicarboxylates (<jats:italic>cf. Table 1, Schemes 3</jats:italic> and <jats:italic>4</jats:italic>). The corresponding heptalenofuran‐1‐one‐type pseudoesters of dimethyl heptalene‐4,5‐dicarboxylates (<jats:italic>Scheme 5</jats:italic>) react with [(phenylsulfonyl)methyl]lithium almost exclusively at C(1) of the furanone group (<jats:italic>Scheme 6</jats:italic>). 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) (<jats:italic>Schemes 6</jats:italic> and <jats:italic>7</jats:italic>). 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 (<jats:italic>Schemes 8</jats:italic>–<jats:italic>13</jats:italic>). The configuration of the addition reaction of the nucleophiles to the inherently chiral heptalenes is discussed in detail (<jats:italic>cf. Schemes 14</jats:italic>–<jats:italic>19</jats:italic>) on the basis of a number of X‐ray crystal‐structure determinations as well as by studies of the temperature‐dependence of the <jats:sup>1</jats:sup>H‐NMR spectra of the addition products.</jats:p> |
Format: | E-Article |
Quelle: | Wiley (CrossRef) |
Sprache: | Englisch |