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- Title
TADDOL-Promoted Enantioselective Intramolecular Diels-Alder Reactions of 1,7,9-Decatrien-3-ones to Octalin Derivatives.
- Authors
Andrä, Michal Sascha; Thiemermann (née Suhrbier), Jutta; Schnaubelt, Jürgen; Lentz, Dieter; Zimmer, Reinhold; Reissig, Hans‐Ulrich
- Abstract
The diastereoselective and enantioselective intramolecular Diels-Alder reactions of 1,7,9-decatrien-3-ones to cisor trans-octalin derivatives were systematically investigated in the presence of different Lewis acids and chiral ligands. The best cis-selective promoter, consisting of diethylaluminum chloride and (R)-1,1'-bi-2-naphthol (BINOL), provided an enantiomeric excess (ee) of only 33%. For the trans-selective reactions, dichlorotitanium diisopropoxide was the best Lewis acid, and a 2-naphthyl-substituted (R,R)-α,α,α',α'-tetraaryl-1,3-dioxolane-4,5-dimethanol ligand (TADDOL) furnished excellent diastereoselectivities and enantioselectivities in the range of 50-68%. Subsequent reactions of a typical trans-octalin derivative led to compounds, which enabled the determination of the absolute configuration of the favored enantiomer and a deduction of the involved reaction mechanism. Interpretation of the NMR shifts of the enantio-enriched Mosher esters and an X-ray structure analysis were the keys for this structural assignment. We could demonstrate that Mosher analyses do not necessarily rely on enantiopure samples.
- Subjects
RING formation (Chemistry); ENANTIOSELECTIVE catalysis; DIELS-Alder reaction; TITANIUM; LEWIS acids
- Publication
European Journal of Organic Chemistry, 2017, Vol 2017, Issue 1, p124
- ISSN
1434-193X
- Publication type
Article
- DOI
10.1002/ejoc.201601068