Diels-Alder additions, tandem regio-/stereoselective

The two successive Diels-Alder additions (tandem cycloadditions) of the C2v-symmetrical tetraene 11 are not regioselective, i.e., mixtures of all the possible regioisomeric bis-adducts are obtained when utilizing non-symmetrical dienophiles. There is no control of the monoadduct on the regio-selectivity of the second cyclo addition. As we have seen with the synthesis of daunomycinone, control of the substitution pattern of the two remote rings A and D of the anthracyclinones can be achieved provided a number of adequate manipulations are carried out with the benzoquinone monoadduct of 11. A more efficient and more versatile way to control the regioselectivity of the tandem cycloadditions is through appropriate and stereoselective double substitutions of tetraene 11. 

Regio-and Stereoselective Tandem Diels-Alder Additions. 198... 

Scheme 7 Regio- and stereoselective tandem Diels-Alder additions...

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See also in sourсe #XX -- [ ]

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