RESUMO
The highly enantioselective Mannich reaction of diazoacetate esters with N-Boc aldimines catalyzed by silver(I) triflate in the presence of (R)-DM-SEGPHOS is reported. The reaction is broad in scope with respect to the (hetero)aromatic aldehyde-derived aldimine and tolerates significant variability of the diazoacetate ester component. Yields and enantioselectivities are good to excellent, and the reaction can be performed on a gram scale with catalyst loadings as low as 1 mol %.
RESUMO
An approach to the indirect measurement of nuclear spin relaxation rates of low-magnetogyric ratio (γ) nuclei using the process of satellite exchange is described. The method does not require the observation of, or even the ability to provide radio-frequency pulses to, the low-γ nucleus, but requires this to be scalar coupled to an NMR observable nucleus, such as 31 P or 1 H, making it especially attractive for the study of diamagnetic transition metals. In situations where spin relaxation is dominated by chemical shift anisotropy (CSA), the determination of the longitudinal spin relaxation time constant (T1 ) of the metal becomes possible, as illustrated for 195 Pt and 107/109 Ag.