CHEM 2211 1st Edition Lecture 27 Outline of Last Lecture I Diels Alder Reactions Outline of Current Lecture I Diels Alder Stereochemistry Lecture Notes I Diels Alder Stereochemistry A ENDO vs EXO i Endo means that the substituents are facing downwards relative to the molecule ii Exo means the substituents are facing upward relative to the molecule iii To visualize endo and exo the compound formed from a diels alder reaction must be drawn in 3D iv The Endo position is the preferred position and is formed the most rapidly B The stereochemistry of the diene and the dienophile don t change during the reaction i The inside substituents the circled hydrogens always point upwards in the ring that forms ii The carbonyl groups are still trans to each other Another example Flipping the dienophile forms the endo enantiomer of the product
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