
TY  - JOUR
A1  - Cambie, RC 
A1  - Higgs, KC 
A1  - Rustenhoven, JJ 
A1  - Rutledge, PS 
T1  - Experiments Directed Towards the Synthesis of Anthracyclinones. XXVIII. Titanium(IV)- and Tin(IV)-Mediated Cyclizations of <I>ortho</I>-Methallyl-Substituted Homochiral Dioxans
JF  - Australian Journal of Chemistry
JO  - Aust. J. Chem.
Y1  - 1996
VL  - 49
IS  - 6
SP  - 677
EP  - 688
KW  - 
UR  - https://doi.org/10.1071/CH9960677 
N2  - 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). 
ER  -

