183663-31-2Relevant academic research and scientific papers
Diels-Alder reactions of chiral 1,3-dienes
Crisp, Geoffrey T.,Gebauer, Markus G.
, p. 8425 - 8431 (1996)
Structurally related 1,3-dienes 3a-f attached to a chiral carbon were treated with maleic anhydride under a variety of conditions. The initial Diels-Alder adducts were not isolated as they spontaneously rearranged to the isomeric isoindolones 6 and 7. The rate of the rearrangement was dependent on the relative stereochemistry of the initial cycloadducts. The π-facial selectivity of the Diels-Alder reaction was determined by analyzing reaction mixtures of the isomeric isoindolones by 1H and 13C NMR spectroscopy and HPLC. A gradual increase in the π-facial selectivity was observed when the homoallylic hydroxyl group of the diene was endowed with a larger protecting group or slightly increased by performing the reactions in ether saturated with LiClO4. These effects were rationalized by proposing a model based on 1,3-allylic strain in the transition state for the dienes 3a-f.
