[2+2+2] CYCLOADDITION REACTION OF 1-METHYLPYRROLE WITH DIETHYL AZODICARBOXYLATE

Reactions of bimolecular [2 + 2 + 2] cycloaddition are of interest since they serve as examples of orbital interactions that can be explained by the Woodward-Hoffmann rules.1 However, concerted [2 + 2 + 2] cycloadditions involving three molecules are rare. For example, trimerization of acetylene to benzene needs a catalyst such as A1C13 and a 1:1 adduct is involved in the course of formation, indicating a stepwise process.2 Although few reports are found in the literature, termolecular [2 + 2 + 2] cycloaddition reactions seem to be useful synthetic processes if a suitable catalyst is employed.3-7We report an example of an uncatalyzed cycloaddition reaction that appears to involve 6 π electrons from three double bonds in three molecules. © 1990, American Chemical Society. All rights reserved.