One of the most widely used reactions in the chemical industry is something called the Diels-Alder reaction, which forms compounds that contain a circle or ring of six atoms, usually carbon, Now, chemist Barry M. Trost of the University of Wisconsin in Madison has discovered a reaction that mimics the Diels-Alder reaction but creates five-membered rings instead of six-membered rings. This new method, reported at PAC CHEM ’84, may streamline the manufacture of several existing drugs and industrial chemicals, says Trost, by cutting down on the number of steps it takes to make the compounds. Trost’s method involves the use of various metal catalysts and a new silicon-containing compound. These substances initiate the formation of a five-membered ring from two molecules, one containing two carbon atoms and an “activator substituent” and the other containing three carbon atoms to which various other chemical groups may be attached. Surprisingly, the catalysts generally control the nature of the products created.