[3+2] cycloadditions of aziridines mechanistical studies

Gaebert C, Mattay J. [3+2] cycloadditions of aziridines mechanistical studies. JOURNAL OF INFORMATION RECORDING. 1996;23(1-2):3-6.The reaction of 1-butyl-2-phenyl aziridine with dimethyl acetylenedicarboxylate under PET conditions yields four products, two isomeric pyrrolidines and the corresponding pyrroles as oxidation products from the pyrrolidines. The reaction of the aziridine with dimethyl maleate and dimethyl fumarate respectively under PET conditions yields pyrroles with retained stereochemistry of the dipolarophiles. The addition of acrylonitrile to 1-butyl-trans-2,3-diphenyl aziridine under PET conditions leads to all four possible isomeric pyrrolidines whereas under direct photolysis only two pyrrolidines are formed. Based on these experimental data the mechanism involving a radical cation will be discussed

[3+2] cycloadditions and nucleophilic additions of aziridines under C-C and C-N bond cleavage

Gaebert C, Mattay J. [3+2] cycloadditions and nucleophilic additions of aziridines under C-C and C-N bond cleavage. Tetrahedron. 1997;53(42):14297-14316.Under PET conditions (photoinduced electron transfer) aziridines react with dipolarophiles in a [3+2] cycloaddition to form five-membered heterocycles. In this study we, used mono- and disubstituted N-alkyl and N-arylaziridines. We noticed that the radical cation as intermediate reacts in a different manner to the classical azomethine ylide. Furthermore, under mild thermal conditions, aziridines react in acetonitrile in a formal [3+2] cycloaddition with activated acetylene derivatives under C-N bond cleavage. Using methanol as solvent, the intermediate is trapped leading to highly substituted enamines. A mechanism for this unexpected thermal reaction is proposed. (C) 1997 Elsevier Science Ltd

Laser flash photolysis of some phenylaziridines

Siegner C, Gaebert C, Mattay J, Steenken S. Laser flash photolysis of some phenylaziridines. JOURNAL OF INFORMATION RECORDING. 1998;24(3-4):253-256.Laser flash photolysis (lambda(exc) = 248 nm) of the aziridines (E)-1-butyl-2,3-diphenylaziridine 1, (E)-2,3-diphenylaziridine 2, 1,2-diphenylaziridine 3 and 1-(p-methoxyphenyl)-2-phenylaziridine 4 were performed in acetonitrile. The reactive intermediates were identified as the corresponding azomethine ylides and spectroscopically and kinetically characterized

Laser flash photolysis of aziridines. Spectroscopic and kinetic characterization of azomethine ylides. Their [3+2] cyclization with alkenes and protonation by water-alcohols to yield iminium ions

Gaebert C, Siegner C, Mattay J, Toubartz M, Steenken S. Laser flash photolysis of aziridines. Spectroscopic and kinetic characterization of azomethine ylides. Their [3+2] cyclization with alkenes and protonation by water-alcohols to yield iminium ions. JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 2. 1998;(12):2735-2740.The reactive intermediates generated by laser flash photolysis (lambda(exc) = 248 or 193 nm) of the aziridines (E)-1-butyl-2,3-diphenylaziridine 1, (E)-2,3-diphenylaziridine 2, 1,2-dliphenylaziridine 3, 1-(p-methoxyphenyl)-2-phenylaziridine 4 and 1-butyl-2-phenylaziridine 5 in acetonitrile and alcohols as solvents were identified as the corresponding azomethine ylides and spectroscopically and kinetically characterized. The rate constants for the [3 + 2] reaction of the ylides with electron-deficient alkenes to give pyrrolidines are between 10(6) and 10(9) M-1 s(-1). In the case of 1 and 2 iminium ions are produced by protonation (by H2O or ROH) of the ylides (also studied by time-resolved conductance). For this reaction, with MeOH as the proton donor, the kinetic isotope effect is k(MeO-H)/k(MeO-D) = 5-7, from which it is concluded that the transition state for protonation of the carbanionic site of the ylide is linear

Formation of radical cations of aziridines generated by laser ash photolysis

Gaebert C, Siegner C, Mattay J, Toubartz M, Steenken S. Formation of radical cations of aziridines generated by laser ash photolysis. PHOTOCHEMICAL & PHOTOBIOLOGICAL SCIENCES. 2004;3(11-12):990-991.The radical cations of 1-butyl-trans-2,3-diphenyl aziridine (1), 1-butyl-2-phenyl aziridine (2), 1,2-diphenyl aziridine (3) and 1-(p-methoxyphenyl)-2-phenyl aziridine (4) were generated upon laser flash photolysis in aqueous and aqueous acetonitrile solutions by direct photoionisation as indicated by the broad absorption band of the solvated electron above 550 nm as well