Bismuth(III) triflate: an economical and environmentally friendly catalyst for the Nazarov reaction.

We describe the use of bismuth(III) triflate as an efficient and environmentally friendly catalyst for the Nazarov reaction of aryl vinyl ketones, leading to the synthesis of 3-aryl-2-ethoxycarbonyl-1-indanones and 3-aryl-1-indanones. By changing the temperature and reaction time, it was possible to modulate the reactivity, allowing the synthesis of two distinct product classes (3-aryl-2-ethoxycarbonyl-1-indanones and 3-aryl-1-indanones) in good to excellent yield. The reaction did not require additives and was insensitive to both air and moisture.

The pitfalls of using spin-spin coupling constants to infer hydrogen bond formation in organofluorine compounds.

Theoretical decomposition of "through space" spin-spin coupling constants (SSCCs) in organofluorine compounds signal that intramolecular hydrogen bonds (H-bonds) are not the primary mechanism of transmission for SSCCs. Increasing solvent polarity may disrupt H-bonds, but not necessarily the SSCC. Substituent effects may drastically alter the SSCC transmission pathway.

One-pot organocatalyzed synthesis of tricyclic indolizines.

Indolizines and their saturated derivatives are important structural motifs present in several biologically active compounds of both natural and synthetic origin. We describe herein a one-pot approach for the synthesis of tricyclic indolizines catalyzed by a bicyclic imidazole-alcohol. The protocol is based on an aqueous Morita-Baylis-Hillman reaction between pyridine-2-carboxaldehydes and six- or seven-membered cyclic enones, followed by sequential intramolecular cyclization and dehydration.

Anthelmintic activity of a nanoformulation based on thiophenes identified in Tagetes patula L. (Asteraceae) against the small ruminant nematode Haemonchus contortus.

The synthesis of thiophenic compounds, previously identified in Tagetes patula, revealed that 4-(5'-(hydroxymethyl)-[2,2'-bithiophene]-5-yl)but-3-yn-1-ol), or simply Thio1, has a pronounced in vitro anthelmintic effect against Haemonchus contortus, showing 100% efficacy in the egg hatch and larval development tests presenting EC = 0.1731 mg.mL and EC = 0.

Through space spin-spin coupling constant transmission pathways in 2-(trifluoromethyl)thiophenol: formation of unusual stabilizing bifurcated CFHS and CFSH interactions.

Given its importance and the possibility of organic F to participate in hydrogen bonds (H-bonds), the understanding of its behavior as a H-bond acceptor with different donors is crucial. The interest in organofluorine compounds and the works related to the study of the participation of this atom in non-covalent interactions is constantly growing. Following recent studies in this subject, we evaluated the existence of two bifurcated intramolecular interactions, a bifurcated CFHS H-bond in the cis conformer of 2-trifluoromethylthiophenol and an unusual, bifurcated CFSH interaction in the trans conformer.

Origin of the Diastereoselectivity of the Heterogeneous Hydrogenation of a Substituted Indolizine.

In this work, the stereoselective heterogeneous hydrogenation of a tetrasubstituted indolizine was studied. Partial hydrogenation products were obtained in three steps from a substituted pyridine-2-carboxaldehyde prepared from commercial pyridoxine hydrochloride. The hydrogenation of the indolizine ring was shown to be diastereoselective, forming and .

Discovery of highly potent and selective antiparasitic new oxadiazole and hydroxy-oxindole small molecule hybrids.

A series of highly active hybrids were discovered as novel antiparasitic agents. Two heterocyclic scaffolds (1,2,4-oxadiazole and 3-hydroxy-2-oxindole) were linked, and the resulting compounds showed in vitro activities against intracellular amastigotes of two protozoan parasites, Trypanosoma cruzi and Leishmania infantum. Their cytotoxicity was assessed using HFF-1 fibroblasts and HepG2 hepatocytes.

Catalyst-Free Conjugate Addition of Indolizines to -Generated Oxidized Morita-Baylis-Hillman Adducts.

Sequential one-pot 2-iodoxybenzoic acid (IBX) oxidation of Morita-Baylis-Hillman (MBH) adducts followed by catalyst-free indolizine conjugate addition was developed. The wide scopes of MBH adducts and indolizines were investigated, and densely functionalized adducts were obtained in yields of up to 94%. The conjugate addition step occurred in less than a minute at room temperature with total regioselectivity toward indolizine C3 carbon.

Intramolecular H-Bond Is Formed in 2-Fluorophenol and 2-Fluorothiophenol, but It May Not Be the Main Pathway of the Coupling Constant Transmission.

The intramolecular CF···HX (X = O or S) H-bond and spin-spin coupling constants (SSCCs) in 2-fluorophenol and 2-fluorothiophenol were investigated experimentally by H and F NMR and theoretically in the framework of the natural bond orbital analysis. In contrast with recent findings from the literature, the results obtained in this work showed that an intramolecular H-bond is formed in the cis conformers and that it has an electrostatic origin. Such an intramolecular electrostatic H-bond is the interaction that rules the conformational preferences on these compounds.

Palladium-Mediated Oxidative Annulation of δ-Indolyl-α,β-Unsaturated Compounds toward the Synthesis of Cyclopenta[ b]indoles and Heterogeneous Hydrogenation To Access Fused Indolines.

The cyclopenta[ b]indole moiety represents a key skeletal unit in several natural and synthetic compounds that exhibit diverse biological properties. We described herein a two-step sequence for synthesizing cyclopenta[ b]indoles with great structural diversity in overall yields up to 37%. The key step was a palladium-catalyzed oxidative annulation of 3-alkylindoles (Fujiwara-Moritani reaction).

Conformational signature of Ishikawa´s reagent using NMR information from diastereotopic fluorines.

The active species of the Ishikawa´s reagent [,-diethyl-(1,1,2,3,3,3-hexafluoropropyl)amine] is a fluorinating hexafluoropropylamine used to convert alcohols into alkyl fluorides. On the other hand, it is also an example of model compound useful to probe conformational preferences using spectroscopic information from diastereotopic fluorines. Moreover, the possibility of experiencing both the generalized anomeric and effects makes the Ishikawa´s reagent an ideal choice to study the governing stereoelectronic interactions of the conformational equilibrium of organofluorine compounds.

Vinyl-1,2,4-oxadiazoles Behave as Nucleophilic Partners in Morita-Baylis-Hillman Reactions.

We describe that vinyl-oxadiazoles function as a new and efficient nucleophilic partner for the Morita-Baylis-Hillman (MBH) reaction. The reaction between 5-vinyl-3-aryl-1,2,4-oxadiazoles and aromatic and aliphatic aldehydes, catalyzed by DABCO in the absence of solvent, showed high efficiency to afford a new class of heterocyclic MBH adducts with potential biological activity on yields up to 99% and short reaction times. These synthetically attractive adducts bear a heterocyclic scaffold of large pharmaceutical and commercial interest associated with a plethora of biological effects and technological applications.