Hydrogenation of 2-vinyl azines 1a-1e in the presence of N-arylsulfonyl imines 2a-2l at ambient temperature and pressure employing cationic rhodium catalysts ligated by tri-2-furylphosphine results in regioselective reductive coupling to furnish branched products of imine addition 3a-3v, which embody modest to high levels of syn-diastereoselectivity. Catalytic coupling of 6-bromo-2-vinylpyridine 1a to imine 2l under an atmosphere of elemental deuterium provides deuterio-3l, with deuterium exclusively at the former beta-position of the vinyl moiety. These data are consistent with a catalytic mechanism involving oxidative coupling of the vinyl azine and imine partners to furnish a cationic aza-rhodacyclopentane, which upon deuteriolytic cleavage releases the adduct and regenerates cationic rhodium(I) to close the catalytic cycle. These studies represent the first metal catalyzed reductive C-C couplings of vinyl azines.

A novel ligand-functionalized adsorbent material was prepared using a combination of radiation-induced graft polymerization (RIGP) and click chemistry (1,3 cycloaddition reaction). The design of the ligand-containing amidoxime functionality is based on its chelating efficiency with uranium. In this process, RIGP is used to graft polymer chains on fiber substrates, where the fibers are prepared by irradiating and treating polyethylene (PE) with different bulk ratios of vinyl benzyl chloride and acrylic acid or itaconic acid. Furthermore, chemical modifications of these fibers are performed using a two-step process, where novel bisimidoxime ligands are incorporated into fibers. These ligands contain imidedioxime, which is known to be a uranophile. Also, the core structure of the ligand containing three donor atoms facilitates the formation of chelate with uranyl ion in media such as seawater. Density functional theory calculations were performed to quantify the binding strength with the uranyl ion. When tested with simulated seawater with a uranium concentration of 6 ppm at pH 8.0−8.3, the developed materials showed moderate to high uranium (∼35−50 g U/kg adsorbent) adsorption capacity.

Imidedioximes are formed in hydroxylamine-treated polyacrylonitrile adsorbents used in the extraction of uranium from seawater. Although known to be a good uranophile, the glutarimidedioxime model compound 1 is rapidly hydrolyzed under acidic conditions used to elute metals from the adsorbent. This work reports the synthesis of a hydrophilic naphthalimidedioxime derivative 14, which is stable under acidic elution conditions. The synthesis starts from simple acenaphthenequinone 7 and converts it to a functional group dense imidedioxime 14 in 7 steps.

Ruthenium catalyzed tert-prenylation of isatin 1 occurs efficiently in the absence of N-protecting groups under the conditions of C-C bond forming transfer hydrogenation employing 1,1-dimethylallene as the prenyl donor. The prenylated adduct, 3-hydroxy-3-tert-prenyl-oxindole 2, is converted to the tertiary neopentyl chloride 3, which participates in nucleophilic substitution by way of an aza-ortho-xylylene intermediate to furnish adducts 4a-4i. Through tertiary neopentyl substitution, two contiguous all carbon quaternary centers are established.Prenylated indole alkaloids have attracted attention due to their remarkable biological effects and challenging structural features. 1 Those incorporating tert-prenyl moieties at the 2-or 3-position include the brevianamides, austamides, paraherquamides, marcfortines, echinulins, aspergamides, norgeamides, avrainvillamides, stephacidins, notamides, roquefortines, as well as the amauromine, ardeemin, and flustramine families of natural products. The construction of indole alkaloids that incorporate a 3-tert-prenyl moiety requires construction of two contiguous all-carbon quaternary centers. Typically, this substructure is installed through the reaction of bis-N-protected tryptophan derivatives with N-(phenylseleno)phthalimide to form 3-phenylselenio-pyrroloindoline adducts, which are ionized with methyl triflate in the presence of prenyl tributylstannane. 2 Considerable pre-activation attends this method, which requires stoichiometric use of both tin and selenium reagents, as well as protection of the indolic nitrogen.In the course of studies aimed at the development of C-C bond forming hydrogenations beyond hydroformylation, 3 we recently developed a suite of catalytic methods for carbonyl allylation, 4 b,d,e,f,i,j,k crotylation 4b,c,g,k and reverse prenylation 4a,b,h,k in the absence of stoichiometric mkrische@mail.utexas.edu. Supporting Information Available. Spectral data for all new compounds ( 1 H NMR, 13 C NMR, IR, HRMS). Single crystal X-ray diffraction data for 4e. This material is available free of charge via the internet at http://pubs.acs.org. NIH Public Access Author ManuscriptOrg Lett. Author manuscript; available in PMC 2010 October 15. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript allylmetal reagents. In the specific case of reverse prenylation, 4a,b,h,k it was found that reductive C-C bond formation is achieved simply upon hydrogenation 4a or transfer hydrogenation 4b,h,k of 1,1-dimethylallene in the presence of carbonyl partners, including isatins. 4a,k Although the synthesis of 3-tert-prenylated oxindoles can be achieved through the addition of n-prenylindium reagents to isatins 5 or through enolate-Claisen rearrangement, 6 N-protected isatins are generally required. 7,8eHere, we report that under the mild conditions of transfer hydrogenation, direct tert-prenylation of isatin occurs in the absence of N-protecting groups. Furthermore, the resulting adduct, 3-hydroxy-3-tert-prenyl-oxindole 2, is readily converted to th...

Category Metal-Catalyzed Asymmetric Synthesis and Stereoselective ReactionsKey words rhodium reductive coupling hydrogenation 2-vinyl pyridines