Let’s face it, using excess of one of two reactants is the essential evil of organic chemistry. While there are understandable thermodynamic arguments to do so (for example, the Le Chatelier principle and the need to drive reversible processes in the desired direction), the use of excess amount of a given chemical in a simple bimolecular reaction is really sub-optimal, especially if it is an irreversible process. When I read papers, I like to pay attention to reaction stoichiometry and I am instinctively drawn to reports that document stoichiometry of 1:1 or close to it. This tells me a lot about the underlying process efficiency (it is green! I hope my student Adam is happy I said that…).
Here is a fairly recent report by Adimurthy et al. This paper is notable for several reasons. It exemplifies proline organocatalysis, but of an unusual type in that the electrophilic component is NOT an aldehyde (which is the usual suspect). Instead, an amide plays the role of an electrophile here, which is cool as we are talking about one of the strongest linkages in chemistry. The reaction is essentially a metathesis because another amide is created. Many examples (if not all) recorded in this work proceed with 1:1 stoichiometry. To me, this speaks to the robust inner workings of this type of activation. I know ammonia is produced, and it is gaseous, and so on, bla bla. I still like this chemistry. This stuff is environmentally benign, which ought to make us all happy. As the Canadian philosopher Marshall MacLuhan (1911-1980) said, “There are no passengers on spaceship earth. We are all crew”. I am being a bit of a sarcastic dweeb now, I know… It’s been a long day.
amphoteros 