The asymmetric borylation of N-tert-butanesulfinyl imines with bis(pinacolato)diboron is achieved using a Cu(II) catalyst and provides access to synthetically useful and pharmaceutically relevant α-amino boronic acid derivatives. The Cu(II)-catalyzed reaction is performed on the benchtop in air at room temperature using commercially available, inexpensive reagents at low catalyst loadings. A variety of N-tert-butanesulfinyl imines, including ketimines, react readily to provide α-sulfinamido boronate esters in good yields and with high stereoselectivity. In addition, this transformation is applied to the straightforward, telescoped synthesis of α-sulfinamido trifluoroborates.

The MgCl(2)-enhanced addition of benzyl zinc reagents to N-tert-butanesulfinyl imines proceeds readily at room temperature to afford the N-tert-butanesulfinyl-protected amine products in good yields and diastereomeric ratios. This method is functional group tolerant in both the imine substrate and benzyl zinc coupling partner. Moreover, benzyl zinc reagent addition to the N-tert-butanesulfinyl imine 3o prepared from isopropylidene-protected glyceraldehyde proceeds in high yield and with exceptional selectivity to provide rapid entry to hydroxyethylamine-based aspartyl protease inhibitors.

The convergent, asymmetric synthesis of vicinal amino alcohols is achieved by the Rh-catalyzed addition of α-amido trifluoroborates to carbonyl compounds.

The rhodium-catalyzed addition of readily accessible arylboroxines to N-tert-butanesulfinyl ketimines derived from oxetan-3-one, N-Boc-azetidin-3-one, and isatins proceeds in high yields with excellent functional group compatibility. Moreover, high diastereoselectivities are observed for the additions to the N-sulfinyl ketimines derived from isatins.

Highly Functional Group Compatible Rh-Catalyzed Addition of Arylboroxines to Activated N-tert-Butanesulfinyl Ketimines. -Arylboroxines with labile functional groups, that are not compatible with Grignard and organolithium reagents, are converted with moderate to excellent yields. The process is applied to oxetanes and azetidines including an asymmetric version which provides high diastereoselectivity to produce interesting pharmacophores. -(JUNG, H. H.; BUESKING, A. W.; ELLMAN*, J. A.; Org. Lett. 13 (2011) 15, 3912-3915, http://dx.doi.org/10.1021/ol201438k ; Dep. Chem., Yale Univ., New Haven, CT 06520, USA; Eng.) -H. Simon