Synthesis and stereochemistry of optically active selenonium imides

The first use of the free selenimide Ph2SeNH as a synthon; the synthesis and X-ray crystal structure of [Ph2SeNSePh2][BPh4]

“…More recently, studies have been performed on optically active tosyl derivatives of selenimides. 10 Although computational investigations into inversion in the free selenimide Ph 2 Se=NH have been undertaken, 11 13 The Se-N distances are shorter than those of typical Se-N single bonds, indicating some degree of multiple bonding, as expected. There is a marked asymmetry within the cation in terms of the Se-N distances, and inspection of the cationanion disposition reveals that close contacts exists between one of the two selenium atoms and the p system of one of the phenyl rings of the [BPh 4 ] − counterion.…”

“…Indeed, given the fact 5 that unstable (ie dialkyl) sulfimides have been used as nitrene (NH) sources before 8 , it may well be that the instability of Ph 2 Se=NH may actually make it a potent reagent in this sense as well. Such potential is magnified by the fact that the chemistry of the related selenium diimides, RN=Se=NR, has 10 also proved to be a fruitful area of investigation, both from structural 15a and synthetic 15b standpoints. Thus work to fully assess the chemistry of this new species is underway.…”

Theoretical studies on the conformations of selenamides

“…They also reported the generation of pyridine N-selenide in the gas phase 3 . Kamigata et al [4][5][6] have reported the syntheses, kinetics, optical activity and Se-N interactions of selenonium imides and R 2 Se=NR with the Se-N hypervalent bond. In contrast, no theoretical studies have been reported on selenamides (also known as selenenamide and selenohydroxylamine) RSe-NR 2 with Se-N single bond.…”

Isolation and Stereochemistry of Optically Active Selenonium Imides

“…The first synthesis of an optically active selenonium imide was reported by Krasnov et al in 1981, but the specific rotation was very low, and the optical purity and absolute configuration were not determined. In 1994, we succeeded in isolating a diastereomerically pure selenonium imide by optical resolution of a diastereomeric selenonium imide with a l -menthyloxycarbonyl group as the chiral source and determined the absolute configuration by comparing the CD spectra of the optically active selenonium imide with those of sulfoxides, sulfonium imides, and selenoxides of known absolute configuration . However, an attempt to transform the diastereomerically pure selenonium imide into the selenonium imide enantiomer by transesterification of the l- menthyl group into an achiral one failed.…”

“…In 1994, we succeeded in isolating a diastereomerically pure selenonium imide by optical resolution of a diastereomeric selenonium imide with a l-menthyloxycarbonyl group as the chiral source and determined the absolute configuration by comparing the CD spectra of the optically active selenonium imide with those of sulfoxides, sulfonium imides, and selenoxides of known absolute configuration. 18 However, an attempt to transform the diastereomerically pure selenonium imide into the selenonium imide enantiomer by transesterification of the l-menthyl group into an achiral one failed. Later, optically active selenonium imide enantiomers were obtained in 80% ee by reacting optically pure selenoxide with toluene-p-sulfonamide 19 or in 20-36% ee by catalytic asymmetric imidation of selenide.…”