Header

UZH-Logo

Maintenance Infos

Alkylation reactions at the benzo moiety of 2,4-Dimethoxy-3-(phenylsulfonyl)benzo[a]heptalenes – model compounds of colchicinoids


El Rayes, S; Linden, A; Abou-Hadeed, K; Hansen, H J (2010). Alkylation reactions at the benzo moiety of 2,4-Dimethoxy-3-(phenylsulfonyl)benzo[a]heptalenes – model compounds of colchicinoids. Helvetica Chimica Acta, 93(10):1894-1911.

Abstract

Alkylation reactions of 3-(X-sulfonyl)benzo[a]heptalene-2,4-diols (X¼Ph, morpholin-4-yl) and their dimethyl ethers were studied. The diols form with K2CO3/MeI in aqueous media the 1-methylated benzoheptalenes, but in yields not surpassing 20% (Table 1). On the other hand, 2,4-dimethoxybenzo[a]heptalenes can easily be lithiated at C(3) with BuLi and then treated with alkyl iodides to give the 3-alkylated forms in good yield (Table 2). Surprising is the reaction with two equiv. or more of t-BuLi since
the alkylation at C(4) is accompanied by the reductive elimination of the X-sulfonyl group at C(3) (Table 3). Most exciting is also the course of 2,4-dimethoxy-3-(phenylsulfonyl)benzo[a]heptalenes in the presence of an excess of MeLi. After the expected exchange of MeO against Me at C(4) (Scheme 6), rearrangement takes place under formation of 4-benzyl-2-methoxybenzo[a]heptalenes and concomitant loss of the sulfonyl group at C(3) (Table 4). In the case of X=morpholin-4-yl, rearrangement cannot
occur. However, the intermediate benzyl anions of Type E (Scheme 8) react easily with O2 of the air to build up corresponding benzo[a]heptalene-4-methanols (Table 6).

Abstract

Alkylation reactions of 3-(X-sulfonyl)benzo[a]heptalene-2,4-diols (X¼Ph, morpholin-4-yl) and their dimethyl ethers were studied. The diols form with K2CO3/MeI in aqueous media the 1-methylated benzoheptalenes, but in yields not surpassing 20% (Table 1). On the other hand, 2,4-dimethoxybenzo[a]heptalenes can easily be lithiated at C(3) with BuLi and then treated with alkyl iodides to give the 3-alkylated forms in good yield (Table 2). Surprising is the reaction with two equiv. or more of t-BuLi since
the alkylation at C(4) is accompanied by the reductive elimination of the X-sulfonyl group at C(3) (Table 3). Most exciting is also the course of 2,4-dimethoxy-3-(phenylsulfonyl)benzo[a]heptalenes in the presence of an excess of MeLi. After the expected exchange of MeO against Me at C(4) (Scheme 6), rearrangement takes place under formation of 4-benzyl-2-methoxybenzo[a]heptalenes and concomitant loss of the sulfonyl group at C(3) (Table 4). In the case of X=morpholin-4-yl, rearrangement cannot
occur. However, the intermediate benzyl anions of Type E (Scheme 8) react easily with O2 of the air to build up corresponding benzo[a]heptalene-4-methanols (Table 6).

Statistics

Citations

Altmetrics

Downloads

2 downloads since deposited on 18 Feb 2011
0 downloads since 12 months
Detailed statistics

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:2010
Deposited On:18 Feb 2011 16:51
Last Modified:05 Apr 2016 14:31
Publisher:Verlag Helvetica Chimica Acta
ISSN:0018-019X
Funders:Swiss National Science Foundation
Publisher DOI:https://doi.org/10.1002/hlca.201000191

Download

Preview Icon on Download
Filetype: PDF (Verlags-PDF) - Registered users only
Size: 926kB
View at publisher

TrendTerms

TrendTerms displays relevant terms of the abstract of this publication and related documents on a map. The terms and their relations were extracted from ZORA using word statistics. Their timelines are taken from ZORA as well. The bubble size of a term is proportional to the number of documents where the term occurs. Red, orange, yellow and green colors are used for terms that occur in the current document; red indicates high interlinkedness of a term with other terms, orange, yellow and green decreasing interlinkedness. Blue is used for terms that have a relation with the terms in this document, but occur in other documents.
You can navigate and zoom the map. Mouse-hovering a term displays its timeline, clicking it yields the associated documents.

Author Collaborations