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Facially dissymmetric maleic anhydride 23 undergoes Diels-Alder cycloaddition with cyclic diene exclusively from the face syn to its etheno-bridges. In addition, the Diels-Alder cycloaddition of 23 with facially dissymmetric exocyclic 1,3-butadiene 47 and 57 were studied. The cycloaddition of 23exhibits high π-facial selectivity. The exocyclic butadienes 47 and 57,however, do not display π-facial selectivity
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