
%0 Journal Article
%A Cambie, RC 
%A Higgs, KC 
%A Rustenhoven, JJ 
%A Rutledge, PS 
%T Experiments Directed Towards the Synthesis of Anthracyclinones. XXVIII. Titanium(IV)- and Tin(IV)-Mediated Cyclizations of <I>ortho</I>-Methallyl-Substituted Homochiral Dioxans
%J Australian Journal of Chemistry
%D 1996/06/01
%V 49
%N 6
%P 677-688
%K 
%R https://doi.org/10.1071/CH9960677
%U https://www.publish.csiro.au/paper/CH9960677 
%X Metal chloride cyclizations of the 4-demethoxy anthraquinonyl 1&#8242;,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&#8242;,3&#8242;-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). 
