For 10 points - identify this method for synthesizing cyclic organic compounds, named for its German co-discoverers.
The mechanism for this reaction is concerted and stereospecific, as two pi bonds are converted into two sigma bonds simultaneously.  Used to produce morphine, cortisone, and other steroids, the simplest reaction of this type is the reaction of 1,3-butadiene and ethylene to from cyclohexene.  For 10 points - identify this method for synthesizing cyclic organic compounds, named for its German co-discoverers.
The mechanism for this reaction is concerted and stereospecific, as two pi bonds are converted into two sigma bonds simultaneously.  
Diels-Alder reaction (Accept: diene synthesis)