SEARCH Articles Figures Tables Boat-like transition states Diels-Alder reactions Diels transition state Diels-Alder reaction endo transition state Diels-Alder reaction transition state structure Transition Diels-Alder Transition state butadiene Diels-Alder reactions Transition state for the Diels-Alder reaction Transition state in Diels-Alder reactions Transition states reactions