Dienophiles norbornane structure

Another stereochemical feature of the Diels-Alder reaction is that the diene and dienophile partners orient so that the endo product, rather than the alternative exo product, is formed. The words endo and exo are used to indicate relative stereochemistry when referring to bicyclic structures like substituted norbornanes (Section 4.9). A substituent on one bridge is said to be exo if it is anti (trans) to the larger of the other two bridges and is said to be endo if it is syn (cis) to the larger of the other two bridges. 

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See also in sourсe #XX -- [ ]

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