Bifunctional acid-base ionic liquid for the one-pot synthesis of fine chemicals: thioethers, 2H-chromenes and 2H-quinoline derivatives

A bifunctional organocatalyst with ionic liquid properties and with an optimized distance between the acid and basic sites efficiently activates electron deficient olefins for 1,4 conjugated addition, which can be incorporated in different one-pot transformations for the preparation of cyclic and acyclic compounds of biological and synthetic interest. More specifically, the catalyst can be successfully applied for different carbon–carbon (Csingle bondC) and carbon–heteroatom (Csingle bondN, Csingle bondO, Csingle bondS) bond forming reactions integrated in a cascade sequence. The activity of the organocatalyst has been compared with that of structurally related monofunctional and bifunctional catalysts. The most attractive features of this procedure are the high atom economy and the use of inexpensive starting materials as well as the use of an environmentally friendly catalyst that can be easily recovered due to its ionic liquid properties.Financial support by Consolider-Ingenio 2010 (project MULTICAT), Spanish MICINN (Projects MAT2011-28009 and CTQ-201127550) and Program Severo Ochoa are gratefully acknowledged.Climent Olmedo, MJ.; Iborra Chornet, S.; Sabater Picot, MJ.; Vidal Castro, JD. (2014). Bifunctional acid-base ionic liquid for the one-pot synthesis of fine chemicals: thioethers, 2H-chromenes and 2H-quinoline derivatives. Applied Catalysis A: General. 481:27-38. https://doi.org/10.1016/j.apcata.2014.05.004S273848

Titanium Salalen Catalysts for the Asymmetric Epoxidation of Terminal (and Other Unactivated) Olefins with Hydrogen Peroxide

The epoxidation of terminal, unconjugated olefins with high stereoselectivity has been a long-standing problem in asymmetric catalysis. In this review, we describe the development of titanium salalen catalysts which provide a practical solution to this problem. This type of epoxidation catalyst employs aqueous hydrogen peroxide as terminal oxidant, which makes this method even more attractive from a preparative point of view. The best salalen ligands for this purpose are derived from cis-DACH as the chiral building block, and the one such ligand incorporating two 3-(pentafluorophenyl)salicylic aldehyde moieties (9c, Berkessel ligand) currently affords the most effective and selective titanium catalyst in this regard. In addition to several examples of the recent use of titanium salalen epoxidation in natural product synthesis, practical hints for catalyst preparation and application are presented. Structural and mechanistic aspects of titanium salalens are briefly addressed as well

Fluorescence reporters for phosphodiesterase activity

A sensitive indicator of nuclease activity is the fluorescence behavior of phosphodiesters 1 and 2. Although 1 and 2 do not fluoresce due to intramolecular quenching, the strongly fluorescent naphthyl phosphates and naphthols are liberated upon hydrolysis. This gives rise to an extremely strong increase in fluorescence intensity. Combined application of 1 and 2 allows detection of phosphatase in addition to phosphodiesterase activity. f = fluorophore, q = quencher

Fluoreszenz-Reporter für Phosphodiesterase-Aktivität

Als empfindlicher Nachweis auf eine Nucleaseaktivität dient das Fluoreszenzverhalten der Phosphorsäurediester 1 und 2. Zwar fluoreszieren 1 und 2 wegen intramolekularer Löschung nicht, doch werden die fluorophoren Naphthylphosphate und Naphthole durch Hydrolyse freigesetzt, was zu einem extrem starken Anstieg der Fluoreszenzintensität führt. Durch kombinierte Anwendung von 1 und 2 wird die Detektion von Phosphatase- neben Phosphodiesteraseaktivität möglich

Probing the scope of the asymmetric dihydroxylation of polymer-bound olefins : monitoring by HRMAS NMR allows for reaction control and on-bead measurement of enantiomeric excess

The aim of this study was (I) to define the scope and limitations of the Sharpless asymmetric dihydroxylation (AD) for polymer-bound olefins of different structural types and (II) to elaborate HRMAS NMR methods for the direct on-bead monitoring of the asymmetric dihydroxylation, including the on-bead determination of enantiomeric excess (ee). (I) 2-Methoxy-4-(2-propenyl)phenol (eugenol, E), 10-undecenoic acid (U), and (E)-4-hydroxystilbene (S) were bound to Wang-resin or TentaGel S-OH. These olefins gave low (E, 32%), intermediate (U, 88%), and very high enantiomeric excesses (S, >99%) when treated with AD mix β in solution. When bound to the polymers, the trend of the enantioselectivities remained the same [S (97%) > U (20−45%) > E (0−3%)]. However, the absolute ee values demonstrate that only the most selective types of substrates in homogeneous solution have practical potential for enantioselective AD on solid phase. (II) HRMAS NMR was successfully used for on-bead monitoring and for the first time for the ee measurement of the polymer-bound dihydroxylation product. As an example, the full assignment of all resonances of polymer-bound 10-undecenoic acid (U) and its dihydroxylation product is presented. For the ee measurement, the polymer-bound dihydroxylation product was derivatized with Mosher's acid. The integration of seven different pairs of resonances in the 13C HRMAS NMR of the diastereomeric Mosher esters gave (in each case) an ee value that agreed within <1% with that determined by chiral HPLC after cleavage of the AD product

Enantiopure N-Benzyloxycarbonyl-beta(2)-amino Acid Allyl Esters from Racemic beta-Lactams by Dynamic Kinetic Resolution using Candida antarctica Lipase B

The dynamic kinetic resolution of alpha-substituted racemic beta-lactams by alcoholytic ring-opening, catalyzed by immobilized lipase B from Candida antarctica is described. With this process, a variety of racemic a-substituted N-Cbz-azetidinones (Cbz = benzyloxycarbonyl) was transformed to the corresponding N-Cbz-protected beta(2)-amino acid allyl esters with high enantioselectivity (up to 99%) and high yields (up to quantitative) at room temperature

Asymmetric cyclopropanation of olefins catalyzed by a chiral cobalt(II) porphyrin

The cobalt(II) complex of the Halterman porphyrin, 5,10,15,20-tetrakis[(1S, 4R, 5R, 8S)-1,2,3,4,5,6,7,8octahydro- 1,4: 5,8-dimethanoanthracene-9-yl] porphyrinato cobalt(II) [Co(por*)], was synthesized and its structure was identified by X-ray analysis. Up to 80: 20 trans: cis diastereomeric ratio and 82% ee were achieved in the cyclopropanation of styrene with ethyl diazoacetate by using this cobalt(II) porphyrin complex as catalyst