Format:
Online-Ressource
ISSN:
1522-2675
Content:
Abstract: It has been found that dimethyl heptalene‐4,5‐dicarboxylates, when treated with 4 mol‐equiv. of lithiated N,N‐dialkylamino methyl sulfones or methyl phenyl sulfone, followed by 4 mol‐equiv. of BuLi in THF in the temperature range of −78 to 20°, give rise to the formation of 3‐[(N,N‐dialkylamino) sulfonyl]‐ or 3‐(phenylsul‐fonyl) benzo[a]heptalene‐2,4‐diols of. (cf. Scheme 4, and Tables 2 and 3). Accompanying products are 2,4‐bis{[(N,N‐dialkylamino) sulfonyl]methyl}‐ or 2,4‐bis[(phenylsulfonyl) methyl]‐4,10a‐dihydro‐3H‐heptaleno[1,10‐bc]furan‐3‐carboxylates as mixtures of diastereoisomers of. cf. Scheme 4, and (Tables 2 and 3) which are the result of a Michael addition reaction of the lithiated methyl sulfones at C (3) of the heptalene‐4,5‐dicarboxylates, followed by (sulfonyl) methylation of the methoxycarbonyl group at C (5) and cyclization of. (cf. Scheme 5). It is assumed that the benzo[a]heptalene formation is due to (sulfonyl) methylation of both methoxycarbonyl groups of the heptalene‐4,5‐dicarboxylates of. (cf. Schemes 6 and 8). The resulting bis‐enolates 35 are deprotonated further. The thus formed tris‐anions 36 can then cyclize to corresponding tris‐anions 37 of cyclopenta[d]heptalenes which, after loss of N,N‐dialkylamido sulfite or phenyl sulfinate, undergo a ring‐enlargement reaction by 1,2‐C migration finally leading to the observed benzo[a]heptalenes of. (cf. Schemes 8 and 9). The structures of the new product types have been finally established by X‐ray crystal‐structure analyses (cf. Figs. 1 and 2 as well as Exper. Part).
In:
volume:80
In:
number:8
In:
year:2004
In:
pages:2535-2564
In:
extent:30
In:
Helvetica chimica acta, New York, NY : Wiley-VCH, 1918-, 80, Heft 8 (2004), 2535-2564 (gesamt 30), 1522-2675
Language:
English
DOI:
10.1002/hlca.19970800821
URN:
urn:nbn:de:101:1-2023112605594103419638
URL:
https://doi.org/10.1002/hlca.19970800821
URL:
https://nbn-resolving.org/urn:nbn:de:101:1-2023112605594103419638
URL:
https://d-nb.info/1311195386/34
URL:
https://doi.org/10.1002/hlca.19970800821
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