Thought I'd give this board some life and get us to exercise our mental muscles a bit
So I'm initiating a Problem of the Week. I'll grab a challenging problem (usually from Evans' site*, but not necessarily). If people seem to like it, I'll try to post one every Monday or so. But I don't have to be the only one posting problems. If anyone else wants to try to challenge the others, go ahead (but lets try to only have one unsolved problem at a time, k?)
So, the inaugural problem. A bit of aldol chemistry, something near and dear to my heart:QUESTION: Provide the transition state which accounts for the observed syn selectivity in the following racemic aldol addition (eq 1). For eq 2, ponder the transition state for the analogous "imine-aldol" addition. Draw the transition state and illustrate the predicted stereochemical outcome of the addition reaction. Assume the imine geometry cannot isomerize under the reaction conditions.
Good luck. I look forward to discussing the answer to the problem, because I came up with a different transition state which gives the wrong answer... but I think I can justify my answer so someone's going to have to talk me out of it.