For half a century the Diels-Alder reaction has served as one of the best methods of synthesis of six-membered carbocycles? The ease of the cycloaddition of diene and dienophile (illustrated below, for example, by the production of 1, 2, 5, 6- tetrahydrobenzaldehyde from the interaction of acrolein with l, &butadiene), the rapid accumulation of polyfunctionality in a relatively small molec-ular framework, the ...