دورية
Experiments Directed Towards the Synthesis of Anthracyclinones. XXVIII. Titanium(IV)- and Tin(IV)-Mediated Cyclizations of ortho-Methallyl-Substituted Homochiral Dioxans
العنوان: | Experiments Directed Towards the Synthesis of Anthracyclinones. XXVIII. Titanium(IV)- and Tin(IV)-Mediated Cyclizations of ortho-Methallyl-Substituted Homochiral Dioxans |
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المؤلفون: | Cambie, RC, Higgs, KC, Rustenhoven, JJ, Rutledge, PS |
المصدر: | Australian Journal of Chemistry; 1996, Vol. 49 Issue: 6 p677-688, 12p |
مستخلص: | Metal chloride cyclizations of the 4-demethoxy anthraquinonyl 1′,3'-dioxan (6) are highly diastereoselective , giving 9-chloro-9-methylanthracyclinones in high yield. The selectivity is inversely proportional to the strength of the Lewis acid, with the mild Lewis acid tin(IV) chloride/ dimethylformamide affording an 82% yield of the diastereomer (21). The predominant products have a (7S) configuration and a trans relationship between the C7 side chain and the 9-chloro substituent. Cyclization of the analogous dimethoxy 1′,3′-dioxan (4) with tin(IV) chloride/ dimethylformamide is considerably less selective, but the major product also has a (7S)-trans stereochemistry. Titanium(IV) chloride effects stereorandom cyclization of (4). |
قاعدة البيانات: | Supplemental Index |
تدمد: | 00049425 14450038 |
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DOI: | 10.1071/CH9960677 |