4,4-Dimethyl-4H-imidazole-5-carbaldehyde oxime 3oxides 4 were prepared by oxidation and nitrosation of 4,5,5-trimethyl-2,5-dihydro-1H-imidazol-1-ols. The oximes 4 were converted to 5-cyano derivatives; the latter react with primary or secondary amines to form 5-(di)alkylamino-4H-imidazole 3-oxides 6. Treatment of 6 with AlkMgX and subsequent oxidation yielded stable nitroxides 4-(di)alkylamino-2,5-dihydroimidazole-1-oxyls 7, the pHsensitive spin probes.

Imidazole derivatives Imidazole derivatives R 0190Grignard Reagent Addition of 5-Alkylamino-4H-imidazole 3-Oxides: Synthesis of New pH-Sensitive Spin Probes. -The pH-sensitive EPR spectra data of the nitroxides are given. Compounds (VIIId), (VIIIe) have higher pK and δaN values than the widely used spin probe ATI. -(KIRILYUK*, I. A.; SHEVELEV, T. G.; MOROZOV, D. A.; KHROMOVSKIH, E. L.; SKURIDIN, N. G.; KHRAMTSOV, V. V.; GRIGOR'EV, I. A.; Synthesis 2003, 6, 871-878; Vorozhtsov Inst. Org. Chem., Sib. Branch Russ. Acad. Sci., Novosibirsk 630090, Russia; Eng.) -C. Herrmann 36-098

α-Organoelement-substituted nitrones have been synthesized for the first time through the reaction of the α-lithiated cyclic aldonitrones of 3-imidazoline 3-oxide, pyrroline 1-oxide, 2H-imidazole 1-oxide, and 3,4-dihydroisoquinoline 2-oxide series with electrophilic reagents such as HgCl2, (CH3)3SiCl, (C2H5)3GeCl, (n-C4H9)3SnBr, Ph2P(O)Cl, Ph2PCl, PhSSPh, PhSeSePh, TsCl, and TsF. Aldonitrones of the 3-imidazoline 3-oxide and pyrroline 1-oxide series were shown to readily afford the products of the lithiation−electrophilic substitution reaction. In contrast, aldonitrones of the 2H-imidazole 1-oxide and 3,4-dihydroisoquinoline 2-oxide series react smoothly only with halogen-free electrophiles. It was found that an aldonitrone group could be lithiated and selectively reacted with electrophiles even when kinetically more acidic methylene and amino groups are present in the molecule. Characteristic features of IR and 13C NMR spectra of the compounds synthesized are discussed. Selected α-organoelement nitrones are characterized by an X-ray diffraction study.