α-Organoelement Nitrones:  Synthesis, Properties, and IR and ¹³C NMR Spectral and X-ray Structural Characterization

Abstract

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, 2 H -imidazole 1-oxide, and 3,4-dihydroisoquinoline 2-oxide series with electrophilic reagents such as HgCl 2, (CH 3 ) 3 SiCl, (C 2 H 5 ) 3 GeCl, ( n -C 4 H 9 ) 3 SnBr, Ph 2 P(O)Cl, Ph 2 PCl, 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 2 H -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 13 C NMR spectra of the compounds synthesized are discussed. Selected α-organoelement nitrones are characterized by an X-ray diffraction study.