First Efficient and General Copper-Catalyzed [2,3]-Rearrangement of Tetrahydropyridinium Ylids

The factors affecting the copper-catalyzed rearrangement of ammonium ylids derived from tetrahydropyridines and diazoesters have been examined,and the first examples of high-yielding metal-catalyzed [2,3]-sigmatropic rearrangements of a wide range of such ylids are reported. The nature of the α-substituent in the diazo component of the reaction has a dramatic effect upon the yields of the reaction, with electron-withdrawing substituents enhancing the yield of the reaction.