Written By: Dr. Sharbil J. Firsan

The greatly desirable goal of achieving high efficiency in chemical synthesis can be approached from several directions, one of which is carrying out a cascade of reactions in one pot, without isolating the intermediates.  This approach reduces the amount of wasted time, materials, and expense associated with working up each reaction in a sequence of reactions.  Dixon and co-workers have recently reported the synthesis of an array of multi-ring heterocycles by a one-pot, N-acyl iminium ion cyclization cascade.  Success in this sequence was achieved through the use of [(C₆H₅)₃P]AuCl/AgOTf as the catalyst system.  Typically, the cascade sequence—an example of which is shown below—is carried out in refluxing toluene in the presence of 1 mol % of the gold catalyst, and leads to yields in the range of 64 to 93%.

(1) Yang, T.; Campbell, L.; Dixon, D. J. J. Am. Chem. Soc. 2007, 129, 12070.