ABSTRACT
A simple three-step access to n/5/m angular tricyclic skeleta from terminal cycloalkenylacetylenes, Cr(CO)(6), and propargylmalonate esters is described. The process involves a cyclopentannulation of propargylmalonates and enynyl Fischer carbenes, followed by a metal-promoted Cope-type fragmentation of the propargyl unit. The resulting 4-allenyl-carbonyl derivatives can undergo either a 5-exo annulation via a tin enolate or an unprecedented gold catalyzed 6-endo cyclization.
Subject(s)
Alkynes/chemistry , Chromium/chemistry , Polycyclic Compounds/chemical synthesis , Catalysis , Cyclization , Gold/chemistry , Malonates/chemistry , Methane/analogs & derivatives , Methane/chemistry , Molecular Structure , Polycyclic Compounds/chemistry , Stereoisomerism , Tin/chemistryABSTRACT
The copper(I)-catalyzed reaction of alkenyldiazoacetates and iminoiodinanes affords functionalized azetine derivatives. This process is consistent with the formation of an aziridinyldiazoacetate intermediate, which gives rise to the four-membered heterocycles by metal-catalyzed ring expansion. The resulting azetine structure is a direct precursor of azeditine-2-carboxylic acid derivatives (EWG = electron-withdrawing group).
Subject(s)
Azetines/chemistry , Copper/chemistry , Diazonium Compounds/chemistry , Imines/chemistry , Catalysis , Cyclization , Halogenation , Molecular Structure , Oxidation-ReductionABSTRACT
The copper(II)-catalyzed reaction of alkenyldiazo compounds with iodosylbenzene leading to ß-oxodiazo derivatives is reported. This process occurs via an unprecedented 1,2-shift of the diazoacetate function. A selection of the synthetic applications of a representative member of this new class of functionalized diazo derivatives in the regioselective synthesis of substituted 1,4-dicarbonyl compounds is also reported.
Subject(s)
Azo Compounds/chemical synthesis , Copper/chemistry , Organometallic Compounds/chemistry , Azo Compounds/chemistry , Catalysis , Molecular Structure , Oxidation-Reduction , StereoisomerismABSTRACT
Tosylhydrazones are useful synthetic intermediates that have been used in organic chemistry for almost 60 years. The recent discovery of a palladium-catalyzed cross-coupling reaction involving a tosylhydrazone coupling partner has triggered renewed interest in these reagents. This reaction shows nearly universal generality with regard to the hydrazone and can be employed for the preparation of polysubstituted alkenes. In the course of this research, novel metal-free C-C and C-O bond-forming reactions have been discovered. Since tosylhydrazones are readily prepared from carbonyl compounds, these transformations offer new synthetic opportunities for the unconventional modification of carbonyl compounds. This Minireview discusses all of these new reactions of a classic reagent.
ABSTRACT
The supramolecular architectures of a fluorophore are controlled through the design of a conjugated polycatenar molecule, the self-assembly of which can be addressed toward a columnar liquid-crystalline phase and organogels. Thus, depending on the environmental conditions for self-assembly, compound CA9 organizes into an unprecedented hexagonal columnar mesophase in the condensed state, in which half a molecule constitutes the slice of the column, or into a rectangular mesomorphic-like organization in the presence of apolar solvents such as cyclohexane and dodecane, at a concentration in which fibers form and gelling conditions are fulfilled. In this Col(r)-type arrangement, the organization within the columns depends on the solvent. All of the materials prepared show luminescence, and moreover, a remarkable 3-fold increase in fluorescence intensity was observed in going from the solution to the gel state.
ABSTRACT
Aryl nonaflates are employed as electrophiles in the Pd-catalyzed cross-coupling with tosylhydrazones affording di-, tri-, and tetrasubstituted olefins. Fine tunning of the reaction conditions are required to accomplish the coupling successfully, including the addition of LiCl and the presence of small amounts of water. Under the optimized conditions, the reactions proceed with high yield and also high stereoselectivity depending on the nature of the coupling partners.
ABSTRACT
The copper(I)-catalyzed regioselective [3 + 2] cyclization of pyridines toward alkenyldiazoacetates leading to functionalized indolizine derivatives is reported. A broad range of pyridine derivatives (including quinoline and isoquinoline) is compatible with this cyclization reaction. The process represents the first successful example of metal-catalyzed cyclization of a π-deficient heterocyclic system with alkenyldiazo compounds.
ABSTRACT
Two new rifabutin analogs, RFA-1 and RFA-2, show high in vitro antimycobacterial activities against Mycobacterium tuberculosis. MIC values of RFA-1 and RFA-2 were ≤0.02 µg/ml against rifamycin-susceptible strains and 0.5 µg/ml against a wide selection of multidrug-resistant strains, compared to ≥50 µg/ml for rifampin and 10 µg/ml for rifabutin. Molecular dynamic studies indicate that the compounds may exert tighter binding to mutants of RNA polymerase that have adapted to the rifamycins.
Subject(s)
Antibiotics, Antitubercular/pharmacology , Drug Resistance, Multiple, Bacterial/drug effects , Mycobacterium tuberculosis/drug effects , Rifabutin/pharmacology , Antibiotics, Antitubercular/chemistry , Microbial Sensitivity Tests , Molecular Structure , Rifabutin/chemistryABSTRACT
Regioselectively substituted indoles are prepared by a Pd-catalyzed C-C/C-N bond-forming sequence from imines and o-dihaloarenes or o-haloarene sulfonates. The heterogeneous reaction as a suspension in water and under microwave heating offers important advantages in comparison with the conventional reaction in an organic solvent, among them, operational simplicity, the employment of KOH solutions instead of alkoxides, and a dramatic reduction of reaction times.
