Quantum-chemistry-aided identification, synthesis and experimental validation of model systems for conformationally controlled reaction studies: Separation of the conformers of 2,3-dibromobuta-1,3-diene in the gas phase

摘要: The Diels-Alder cycloaddition, in which a diene reacts with dienophile to form cyclic compound, counts among the most important tools organic synthesis. Achieving precise understanding of its mechanistic details on quantum level requires new experimental and theoretical methods. Here, we present an approach that separates different conformers molecular beam as prerequisite for investigation their individual cycloaddition reaction kinetics dynamics under single-collision conditions gas phase. A low- high-level quantum-chemistry-based screening more than one hundred dienes identified 2,3-dibromobutadiene (DBB) optimal candidate efficient separation gauche s-trans by electrostatic deflection. preparation method DBB was developed enabled generation dense beams this compound. predictions properties were validated successful beam. marked difference photofragment ion yields two upon femtosecond-laser pulse ionization observed, pointing at pronounced conformer-specific fragmentation ionized DBB. Our work sets stage rigorous examination models reactions controlled