Luis D. Miranda

Efficient, intermolecular, oxidative radical alkylation of heteroaromatic systems under "tin-free" conditions.

Novel and efficient radical alkylation of several heterocyclic systems including pyrroles, indoles, furan and thiophenes is described using xanthate based radical chemistry. The present methodology could be used to provide rapid access to various nonsteroidal antiinflammatory drugs.

Two-step synthesis of 2,3-dihydropyrroles via a formal 5-endo cycloisomerization of Ugi 4-CR/propargyl adducts.

A practical two-step synthesis of 2,3-dihydropyrroles from Ugi 4-CR/propargyl adducts is presented. The protocol includes a base-mediated formation of an allenamide functional group and an in situ metal-free formal 5-endo cycloisomerization that occurs in a highly regioselective manner at the allenamide C-γ.

A tandem carbonylation/cyclization radical process of 1-(2-iodoethyl)indoles and pyrrole

Abstract The AIBN-induced radical reaction of 1-(2-iodoethyl)indoles and pyrroles with Bu 3 SnH under 80 atm of CO was examined. Carbon monoxide was efficiently trapped by an alkyl radical to form an acyl radical which underwent intramolecular addition to the aromatic system to produce bicyclic aromatic ketones after in situ oxidation.

A tandem radical addition/cyclization process of 1-(2-iodoethyl)indoles and methyl acrylate

Abstract Benzindolizidine systems are generated in moderate yields by a hexabutylditin mediated consecutive radical addition, cyclization, oxidation process from 1-(2-iodoethyl)indoles and methyl acrylate.

Intramolecular radical acylation of 2-methylsulfonylpyrroles

Abstract Primary alkyl radicals generated (AIBN/Bu 3 SnH) from 1-(2- or 3-haloalkyl)-2-methylsulfonylpyrroles are intercepted by CO (80 atm), and the acyl radicals so produced undergo intramolecular oxidative cyclization at the α-position, giving bicyclic ketones with retention or loss of the sulfonyl moiety.

Multicomponent/Palladium-Catalyzed Cascade Entry to Benzopyrrolizidine Derivatives: Synthesis and Antioxidant Evaluation.

A versatile and efficient protocol for the synthesis of highly substituted benzopyrrolizidines (tetrahydro-3H-pyrrolo[2,1-a]isoindol-3-ones) is reported. The strategy consisted of an Ugi four-component reaction/elimination methodology to afford dehydroalanines containing trans-cinnamic acid derivatives and different substituted 2-bromobenzylamines, followed by a palladium-catalyzed 5-exo-trig/5-exo-trig cascade carbocyclization process. Gratifyingly, benzopyrrolizidines were obtained in moderate to good yields (42-77%) with a Z geometry due to the structural requirements for syn-β-hydride elimination. The prepared heterocyclic scaffolds are decorated with several substituents and incorporate a benzopyrrolizidine-fused system, along with an embedded cinnamic acid derivative, two privileged medicinal chemistry scaffolds. Additionally, since some of the compounds are derived from the well-known antioxidants ferulic and sinapinic acids, they were tested for their in vitro antioxidant capacity. The data suggested that compounds having a p-hydroxyl group showed moderate 2,2-diphenyl-1-picrylhydrazyl-radical-scavenging activity and were effective antioxidants in preventing lipoperoxidation in a thiobarbituric acid reactive substances assay.

Oxidative radical cyclization on enamide systems using n-Bu3SnH and dilauroyl peroxide

Abstract Efficient 5- endo and 6- endo oxidative radical cyclizations on enamide systems are described using nBu 3 SnH and dilauroyl peroxide both as initiator and oxidant. Dibenzoyl peroxide and dicumyl peroxide were also tested in the same reaction and the product yields were very similar to those obtained with dilauroyl peroxide. The erythrina ring system was constructed in a two-step sequence featuring this novel process.

Microwave-assisted C-3 selective oxidative radical alkylation of flavones

Flavones were directly alkylated at the C-3 position in moderate yields using a xanthate-based oxidative radical addition procedure. This methodology is a suitable synthetic tool for the direct substitution of the vinylic and unactivated C-H bond of the C ring of the flavone by an alkyl functionality under neutral conditions.

meso-Dihydroguaiaretic acid derivatives with antibacterial and antimycobacterial activity

Thirty-three meso-dihydroguaiaretic acid (meso-DGA) derivatives bearing esters, ethers, and amino-ethers were synthesized. All derivatives were tested against twelve drug-resistant clinical isolates of Gram-positive and Gram-negative bacteria, including sensitive (H37Rv) and multidrug-resistant Mycobacterium tuberculosis strains. Among the tested compounds, four esters (7, 11, 13, and 17), one ether (23), and three amino-ethers (30, 31, and 33) exhibited moderate activity against methicillin-resistant Staphylococcus aureus, whereas 30 and 31 showed better results than levofloxacin against vancomycin-resistant Enterococcus faecium. Additionally, nineteen meso-DGA derivatives displayed moderate to potent activity against M. tuberculosis H37Rv with minimum inhibitory concentration (MIC) values ranging from 3.125 to 50µg/mL. Seven meso-DGA derivatives bearing amino-ethers (26-31 and 33) exhibited the lowest MICs against M. tuberculosis H37Rv and G122 strains, with 31 being as potent as ethambutol (MICs of 3.125 and 6.25µg/mL). The presence of positively charged group precursors possessing steric and hydrophobic features (e.g. N-ethylpiperidine moieties in meso-31) resulted essential to significantly increase the antimycobacterial properties of parent meso-DGA as supported by the R-group pharmacophoric and field-based QSAR analyses. To investigate the safety profile of the antimycobacterial compounds, cytotoxicity on Vero cells was determined. The amino-ether 31 exhibited a selectivity index value of 23, which indicate it was more toxic to M. tuberculosis than to mammalian cells. Therefore, 31 can be considered as a promising antitubercular agent for further studies.

Crystal structure of ethyl 2,4-di­chloro­quinoline-3-carboxyl­ate

In the crystal structure of the title compound, C12H9Cl2NO2, the mean planes through the quinoline and carboxylate groups have r.m.s. deviations of 0.006 and 0.021 Å, respectively, and form a dihedral angle of 87.06 (19)°. In the crystal, molecules are linked via very weak C—H⋯O hydrogen bonds, forming chains, which propagate along the c-axis direction.