RESUMO
The design of a radical relay chaperone to promote selective C-H functionalizations is described. A saccharin-based imine was found to be uniquely suited to effect C-H amination of alcohols via an in situ generated hemiaminal. This radical chaperone facilitates the mild generation of an N-centered radical while also directing its regioselective H atom transfer (HAT) to the ß carbon of an alcohol. Upon ß C-H halogenation, aminocyclization, and reductive cleavage, an NH2 is formally added vicinal to an alcohol. The development, synthetic utility, and chemo-, regio-, and stereoselectivity of this imine chaperone-mediated C-H amination is presented herein.
Assuntos
Álcoois/química , Iminas/síntese química , Chaperonas Moleculares/síntese química , Radicais Livres/química , Iminas/química , Chaperonas Moleculares/química , Estrutura MolecularRESUMO
An efficient enantioselective hypervalent iodine promoted oxylactonization of 4-pentenoic acids has been achieved using stoichiometric or a catalytic amount of chiral aryl-λ3-iodane. This reaction provides straightforward access to a wide range of sulfonyloxy- and phosphoryloxy-γ-butyrolactones in respectable yields with moderate to excellent enantioselectivities.
RESUMO
Asymmetric [3 + 2] cycloaddition of quinones with ene- and thioene-carbamates was achieved by chiral phosphoric acid catalysis, providing the corresponding 3-amino-2,3-dihydrobenzofurans in excellent yields with moderate to good diastereoselectivities and excellent enantioselectivities. An asymmetric tandem oxidative cycloaddition protocol starting from hydroquinones was also accomplished with phenyliodine(III) diacetate and a chiral phosphoric acid in the same reaction vessel.
RESUMO
A general and practical N-iodosuccinimide (NIS)-promoted aza-Friedel-Crafts reaction of various aromatic nucleophiles with N-acylimines generated in situ from α-amidosulfides to give a rapid access to highly functionalized amines is described. The newly developed methodology is very mild, fast, efficient, and complementary.
RESUMO
A general and practical CAN-mediated oxidative radical α-coupling reaction of various imine surrogates with allylsilanes has been described. This multicomponent process affords ß-allylated α-carbamido ethers as stable imine precursors in respectable yields under mild conditions.
Assuntos
Carbamatos/síntese química , Cério/química , Iminas/química , Nitratos/química , Carbamatos/química , Catálise , Estrutura Molecular , Silanos/química , EstereoisomerismoRESUMO
Highly enantio- and diastereoselective three-component inverse electron-demand aza-Diels-Alder reaction of aldehydes, anilines, and isoeugenol derivatives catalyzed by a chiral phosphoric acid catalyst are reported. A wide variety of 2,3,4-trisubstituted tetrahydroquinolines containing an aryl group at the 4-position were obtained in a one-pot process with good to high yields and excellent stereoselectivities (>95:5 dr and up to >99% ee).