137465-87-3Relevant academic research and scientific papers
Solvent effect on the sensitized photooxygenation of cyclic and acyclic α-diimines
Lemp, Else,Zanocco, Antonio L.,Günther, German,Pizarro, Nancy
, p. 10734 - 10746 (2007/10/03)
The reaction of singlet molecular oxygen with a series of cyclic and acyclic α-diimines was studied. Time-resolved methods were used to measure total reaction rate constants and steady-state methods were used to determine chemical reaction rate constants. GC-MS was used to tentatively assign the reaction products. 5,6-Disubstituted cyclic α-diimines are singlet oxygen quenchers, but become more effective in polar solvents. A reaction mechanism involving a perepoxide intermediate or transition state leading to a hydroperoxide seems to be a key reaction path for product formation. A replacement of the phenyl substituent for a methyl substituent opens up an additional reaction involving a perepoxide-like exciplex, which increases singlet oxygen quenching of the cyclic α-diimines. The reactivity of 5,6-disubstituted cyclic α-diimines towards singlet oxygen is highly dependent on steric interactions arising from vicinal phenyl rings and from electronic effects. 1,4-Disubstituted acyclic α-diimines are, by comparison, moderate or poor singlet oxygen quenchers. Total rate constants are scarcely dependent on solvent properties, but instead correlate with the Hildebrand parameter. These results are explained in terms of a mechanism involving a dioxetane-like exciplex that gives rise to a charged intermediate leading to products.
Photooxygenation of 1,4-Diaza-1,3-butadienes (α-Diimines): Formation of Isonitriles
Gollnick, Klaus,Koegler, Sigrid,Maurer, Dorothee
, p. 229 - 234 (2007/10/02)
Dye-sensitized photooxygenations of cyclic and acyclic 1,4-diaza-1,3-butadienes (α-Diimines), carrying a methyl or an ethyl group in the 2-position, yield isonitriles and amides, as well as formaldehyde or acetaldehyde.Thus, cyclic α-diimines such as 5,6-dimethyl- (1a), 5-methyl-6-phenyl- (1b), 5-methyl-6-(p-tolyl)- (1c), and 5,6-diethyl-2,3-dihydropyrazine (1d) yield the respective 1-isocyano-2-(acylamino)ethanes 2a-d, whereas 5-isopropyl-6-phenyl- (1e) and 5,6-diphenyl-2,3-dihydropyrazine (1f) are inert toward photooxygenation.Acyclic α-diimines such as 1,8-bis(acetylamino)-3,6-diaza-4,5-dimethyl-3,5-octadiene (4a), 2,5-diaza-3,4-dimethyl-2,4-hexadiene (4b), 1,4-diaza-2,3-dimethyl-1,4-diphenyl-1,3-butadiene (4c), and N,N'-bis-2,3-butanediimine (4d) afford the respective isonitriles 5a-d and acetamides 6a-d.With retention of configuration, chiral α-diimines such as (-)-N,N'-bis-2,3-butanediimine and its R,R enantiomer , and (3S,8S)-(-)-3,8-dicarbomethoxy-4,7-diaza-2,5,6,9-tetramethyl-4,6-decadiene yield the corresponding enantiomerically pure isonitriles (S)-5e, (R)-5e, and (S)-5f and acetamides (S)-6e, (R)-6e, and (S)-6f.Evidence for a singlet oxygen reaction is presented.A working hypothesis is proposed which includes the formation of a transient hydroperoxide 7 that fragments into an isonitrile molecule, an aldehyde, and an N-alkyl- or N-arylnitrilium cation and a hydroxide ion; the latter combine to yield the amide groups in 2a-d and the amide compounds 6a-f.
