Chiral diselenide ligands for the asymmetric copper-catalyzed conjugate addition of Grignard reagents to enones

Organoselenium(ii) halides containing the pincer 2,6-(Me2NCH2)2C6H3ligand – an experimental and theoretical investigation

“…Singlet 1 H and 13 C signals were observed both for the methylene and methyl protons and carbons, respectively, indicating equivalence of the two pendant arms and a high symmetry of the cation on the NMR time scale due to a fast conformational change of the chelate five-membered SeC 3 N rings. For compounds 5-8, typical 1 H (sometimes overlapped) and 13 C resonances were observed for the organic groups in the anion. In the case of 5 the spectra show broad 1 H resonances for the methyl and methylene protons in anion [2-{(Me 2 NCH 2 )C 6 H 4 } 2 SbCl 2 ] − .…”

“…The atoms are drawn with 50% probability ellipsoids [symmetry equivalent atoms (1 − x, y, 1.5 − z), (−0.5 + x, 0.5 + y, z), (−0.5 + x, −0.5 + y, z) and (1.5 − x, −0.5 + y, 1.5 − z) are given by "prime", "a", "b" and "c", respectively]. The organoselenium compounds 1-8 were investigated in solution by multinuclear NMR spectroscopy ( 1 H, 13 C, 77 Se) and the 1 H and 13 C resonances were assigned based on 2D experiments, according to the numbering scheme illustrated in Scheme 3.…”

“…The 1 H, 13 (COSY, HSQC and HMBC) which were performed using standard pulse sequences in the version with z-gradients, as delivered by Bruker with TopSpin 1.3 PL6 spectrometer control and processing software. The 77 Se spectra were obtained using diphenyldiselenide as an external standard.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] While one pendant arm ligands such as 2-(Me 2 NCH 2 )C 6 H 4 , 2-[E(CH 2 CH 2 ) 2 NCH 2 ]C 6 H 4 (E = O, NMe), 2-(2′-oxazolinyl)phenyl, 2-(RNvCH)C 6 H 4 or related ones were quite often used in organoselenium chemistry, only a few compounds containing "pincer" aromatic groups have been reported. 1,6 Examples include mainly organic groups with oxygen as a potential donor atom in the pendant arm, e.g.…”

“…All new compounds were investigated in solution by multinuclear NMR spectroscopy ( 1 H, 13 and Electron Localization Function (ELF) jointly to a Natural Bond Orbital (NBO) approach was used to shed light on the effect of the nature of the halogen species X on the bonding within the 3c-4e N-Se-N moiety.…”