
TY  - JOUR
A1  - Bercich, Mark D. 
A1  - Cambie, Richard C. 
A1  - Rutledge, Peter S. 
T1  - Experiments Directed Towards the Synthesis of Anthracyclinones. XXXIV Hetero-Diels&#8211;Alder Reactions Using Chiral Boron and Titanium Reagents
JF  - Australian Journal of Chemistry
JO  - Aust. J. Chem.
Y1  - 1999
VL  - 52
IS  - 9
SP  - 851
EP  - 860
KW  - 
UR  - https://doi.org/10.1071/CH98181 
N2  - Reactions between benzaldehyde or o-anisaldehyde and a series of silyloxy dienes catalysed by the chiral acyl- oxyborane (CAB) complex (4) give high yields of enantioselective products from a Mukaiyama aldol rather than a hetero-Diels&#8211;Alder reaction. Attempts to effect a similar catalytic reaction with anthraquinone aldehydes were unsuccessful but use of 2 equiv. of the CAB complex (1) followed by cyclization promotes a formal hetero- Diels&#8211;Alder reaction between the aldehyde (7) and the diene (12) to give the dihydropyrone (24) in 45&percnt; yield and with a 79&percnt; e.e. in favour of the 2'R enantiomer. Hetero-Diels&#8211;Alder reactions between the aldehyde (7) and the diene (12) using the chiral titanium complexes Ti&lsqb;(R)-BINOL&rsqb;Cl 2 , Ti&lsqb;(R,R)-TADDOL&rsqb;Cl 2 and Ti&lsqb;(R)-BINOL&rsqb; 2 have been investigated. The first two complexes promote the reaction at &minus;30 and &minus;78&#176; respectively but with low induced enantioselectivities. 
ER  -

