A multistep flow process for the synthesis of highly functionalized benzoxazoles.

An efficient and scalable transformation of 3-halo-N-acyl anilines to the corresponding benzoxazoles within a continuous flow reactor is reported. This transformation proceeds via base-mediated deprotonation, ortho-lithiation, and intramolecular cyclization to provide unstable lithiated benzoxazole moieties. The subsequent in-line electrophilic quench results in the formation of substituted benzoxazoles in high yield and quality. Continuous flow technology allowed for accurate temperature control and immediate in-line quench while minimizing the hold-up time for the unstable lithiated intermediates thereby minimizing associated byproduct formation.

KMnO(4)-Mediated oxidation as a continuous flow process.

An efficient and easily scalable transformation of alcohols and aldehydes to carboxylic acids and nitroalkane derivatives to the corresponding carbonyls and carboxylic acids using permanganate as the oxidant within a continuous flow reactor is reported. Notably, the generation and downstream processing of MnO(2) slurries was not found to cause any blocking of the reactor when ultrasound pulses were applied to the flow system.

C1-symmetric oxazolinyl sulfoximines as ligands in copper-catalyzed asymmetric mukaiyama aldol reactions.

Aryl-bridged C1-symmetric oxazolinyl sulfoximines are applicable in copper-catalyzed asymmetric Mukaiyama aldol reactions with methyl pyruvate. The resulting alpha-hydroxy esters have been obtained with up to 94% ee in good yields. They contain a quaternary stereogenic center and represent valuable precursors for biologically active molecules.

Application of beta-hydroxysulfoximines in catalytic asymmetric phenyl transfer reactions for the synthesis of diarylmethanols.

Enantiomerically enriched diarylmethanols have been prepared by catalyzed asymmetric phenyl transfer reactions onto aromatic aldehydes with use of readily available beta-hydroxysulfoximines as catalysts. As the aryl source, combinations of diethylzinc with either diphenylzinc or triphenylborane have been applied affording arylphenylmethanols with up to 93% ee in good yields. Various functionalized aldehydes and heterocyclic substrates are tolerated, yielding synthetically relevant products.

Efficient copper-catalyzed N-arylation of sulfoximines with aryl iodides and aryl bromides.

Two simple and inexpensive systems for copper-catalyzed N-arylations of sulfoximines with aryl bromides and aryl iodides have been developed. Using 10 mol % of a copper(I) salt in combination with 20 mol % of a 1,2-diamine and Cs2CO3 provides N-arylated sulfoximines in high yields. Various functional groups and heteroatoms are tolerated. The method is complementary to the known protocols for N-arylations of sulfoximines, which require stoichiometric quantities of copper salts or cost-intensive palladium/BINAP catalysts.