One of the great things about my department is the seminar program, and over the last three years, we have had some outstanding scientists and speakers, including two Nobel laureates (Grubbs and Sharpless). Other stalwarts include KCN, Harry Gray, and Amos Smith.
However, I intentionally made a distinction between good scientists and good speakers, because not all good scientists are good speakers, and vice versa. I don't recount any good visiting scientist who was an absolutely egregious speaker, but there were still clear shades of distinction. One of the illusions that was dispelled for me was that as a research student, you don't always necessarily learn the most from the biggest names in the field. That's because many times, their talks are like their review articles. For example, KCN's talk was good, but it wasn't anything that we did not know from his website and his reviews (and there are many, aren't there?). However, for speakers like him, the choice of topic is also a bit understandable, since the whole department is going to turn out to listen to them, and they want to have something for each one. But understandably, that does not leave much new or enlightening material for the special-interest student.
So, given the above paradigm, it was interestingly some less-known but upcoming names that provided both the most entertainment and the most information for me. There is also a special treat in listening to a young and dynamic assistant professor which clearly distinguishes his talk from that of a KCN, or a Grubbs. The bottom line is that years after I graduate, even though I will remember the fact that KCN and Grubbs gave talks, the talks whose content and style I will remember the most will be those given by unexpectedly enlightening and especially young speakers. Until now, here are the speakers whose work and talks have especially stuck out in my mind:
Sergey Kozmin (University of Chicago): His investigation of Gold catalysed cyclizations and his synthesis of Leucoscandrolide involving a 'spontaneous' macrcyclization was most impressive. His style was dynamic and riveting.
Jeffrey Bode (UCSB): His use of thazolium and related nucleophiles was very creative. His new method of peptide bond formation was highlighted in C & EN's Highlights of 2006.
Erik Sorensen (Princeton): His investigations into concise total syntheses, and his use of phenolic coupling took me back to my well-taught biosynthesis master's degree class. Excellent chemistry and syntheses.