Enantioselective catalytic conjugate addition of dialkylzinc reagents using copperphosphoramidite complexes; Ligand variation and non-linear effects Arnold, L.A.; Imbos, R.; Mandoli, A.; de Vries, A.H.M.; Naasz, R.; Feringa, B.L.

Novel chiral Er complexes based on both enantiomers of extended i PrPyBox (2,]pyridine) show strong near-infrared circularly polarized luminescence (CPL) within the 1400 to 1600 nm spectral region under 450 nm irradiation. CPL activity in this region, despite being particularly rare, would open the way to potential applications in the domain, e.g., of fiber-optic telecommunications and free-space long-distance optical communications employing circularly polarized light. Moreover, the long wavelength excitation is advantageous for applications in the field of (circularly polarized) microscopy and bioimaging.

Abstract:The explosively-growing applications of the Cu-catalyzed Huisgen 1,3-dipolar cycloaddition reaction between organic azides and alkynes (CuAAC) have stimulated an impressive number of reports, in the last years, focusing on recoverable variants of the homogeneous or quasi-homogeneous catalysts. Recent advances in the field are reviewed, with particular emphasis on systems immobilized onto polymeric organic or inorganic supports.

Radical copolymerisation of divinylbenzene and a properly modified enantiomerically pure imidazolidinone inside a stainless steel column in the presence of dodecanol and toluene as porogens afforded the first example of a chiral organocatalyst immobilized onto a monolithic reactor. Organocatalyzed cycloadditions between cyclopentadiene and cinnamic aldehyde were performed under continuous-flow conditions; by optimizing the experimental set up, excellent enantioselectivities (90% ee at 25 [degree]C) and high productivities (higher than 330) were obtained, thus showing that a catalytic reactor may work efficiently to continuously produce enantiomerically enriched compounds. The same catalytic reactor was also employed to carry out three different stereoselective transformations in continuo, sequentially, inside the chiral column (Diels-Alder, 1,3-dipolar nitrone-olefin cycloaddition, and Friedel-Crafts alkylation); excellent results were obtained in the case of the former two reactions (up to 99% yield, 93% ee and 71% yield, 90% ee, at 25 [degree]C, respectively). In addition to simplify the product recovery, the monolithic reactor performed better than the same supported organocatalyst in a stirred flask and could be kept working continuously for more than 8 days