This is definitely the most famous name reaction for which the selection rules of Woodward and Hoffmann apply.
The oxo variant of this reaction is used to construct dihydropyran from carbonyl groups. The stereo- and regiochemistry of this reaction can be predicted using rules named for one of its namesakes and Stein, which is also known as the cis principle. This is definitely the most famous name reaction for which the selection rules of Woodward and Hoffmann apply. Interestingly, this reaction involves the interaction of the HOMO of one reactant and the LUMO of the other, a situation that is reversed in its "inverse demand" form. Danishefsky's reagent and maleic anhydride are commonly used reactants for this reaction. Because the stereoisomer in this concerted/pericyclic reaction depends on whether the reactants are aligned or staggered in the transition state, the endo state is kinetically favored. For 10 points, identify this doubly-eponymous reaction in which a cyclohexene is produced from the cycloaddition of a conjugated diene and an alkene, or dienophile
The oxo variant of this reaction is used to construct dihydropyran from carbonyl groups.
Diels-Alder reaction [prompt on [4+2] cycloaddition]