The idea of decreasing surface area via "enforced hydrophobic interactions" was originally posited t
The idea of decreasing surface area via "enforced hydrophobic interactions" was originally posited to explain the acceleration of this reaction in water by Breslow. In cases where one of the reactants in this reaction is also a cyclic ketone, it may be followed by the often-aromatizing cheletropic extrusion of carbon monoxide. Pyridine and pyran derivatives are accessible through variants of this reaction which use imines and ketones respectively. The HOMO-LUMO overlap of its two reactants usually explains why this reaction has a strong preference for the electron-withdrawing groups of one reactant pointing down and inward in the transition state; that is called the "endo" rule. For 10 points, name this [4+2] cycloaddition that forms cyclohexene derivatives from dienes and dienophiles.