Reactions that form 6 membered rings most commonly go via either boat or chair transition states but the products themselves do not necessarily adopt the same conformation as the TS.
I'm attempting to model a cyclisation in which an amine attacks a pi system to form a new ring, giving rise to two diasteromers depending on which face of the pi system is attacked.
The products have been explored (MM conformational search then QM optimisation of all low energy conformers) and are both chairs (the boat being significantly high in energy as to be essentially unpopulated).
In the reaction of interest there is precedence in the literature from computational studies that the reactions can go via either boats or chairs (depending on the exact structure) and so I would ideally like to find both possible transition states leading to each diastereomer.
My initial plan was to start with the product and work backwards (the transition state is thought to be late, meaning it should resemble the product) , elongating the bond by x angstroms (optimising at each step whilst constraining the distance) and then looking for a 'maximum' from which I would then optimise to a TS however this doesn't provide a method for me to find the boat TS's.
How does one go about finding all possible transition states? Is it valid for me to find a high energy boat conformation of the product and apply the same bond lengthening exercise?