Nucleophilic attack at αβ-unsaturated carbonyl systems. The reactions of acrolein and methyl acrylate with CF3O–, [F–⋯ HOMe], RO–, and [RO–⋯ HOR]. An ab initio and ion cyclotron resonance study

Abstract

Ab initio calculations suggest that the fluoride negative ion should react with acrolein to form a number of potentially stable [M + F^–] ions. These include a number of ‘solvated’ ions together with those formed by conjugate addition, and addition to the carbonyl centre. The energies of many of these species relative to reactants are low and comparable (–130 to –180 kJ mol^–1) and it is likely that they will be in equilibrium unless collisional deactivation removes the excessive energy of the system. Acrolein reacts with the fluoride ion donors CF₃O^– and [F^–⋯ HOMe] to give detectable [M + F^–] ions, and with MeO^– and [MeO^–⋯ HOMe] to yield [M + MeO^–] species. There is no experimental evidence available to suggest structures for these species. The methoxide negative ion deprotonates acrolein and methyl acrylate to produce allenic ions [CH₂CC(R)(O^–)](not the corresponding species [CH₂C–COR]) and these ions undergo a number of complex reactions with the neutral substrate. The CD₃O^– negative ion reacts with methyl acrylate [α-²H₁](CH₂CD–CO₂Me) to yield both stable and decomposing [M + CD₃O^–] species. The decomposing adduct yields both [CH₂CC(OMe)(O^–)] and [CH₂CC(OCD₃)(O^–)] by a reaction sequence which must involve the intermediacy of the tetrahedral species (CH₂CH)(MeO)(CD₃O)C^–O^–