ABSTRACT
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.
Subject(s)
Borates/chemical synthesis , Boron Compounds/chemistry , Boronic Acids/chemical synthesis , Butanones/chemistry , Copper/chemistry , Imines/chemistry , Sulfonamides/chemical synthesis , Boronic Acids/chemistry , Catalysis , Molecular Structure , Stereoisomerism , Sulfonamides/chemistryABSTRACT
Arylboroxines, which are easily accessed by drying commercially available arylboronic acids, are added to N-(isopropanesulfinyl)ketimines derived from cyclohexanone, N-Boc-piperidin-4-one, and tetrahydropyran-4-one in high yields and with excellent functional group compatibility via rhodium catalysis. These results contrast with additions to the corresponding ketimines incorporating the larger N-tert-butanesulfinyl group, which give considerably lower yields. Efficient two-step preparation of racemic isopropanesulfinamide from inexpensive isopropyl disulfide and recycling of the isopropanesulfinyl group from the addition products are also described.
ABSTRACT
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.
ABSTRACT
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.
