Chemical constituents and allelopathic activity of Machaerium eriocarpum Benth.

Abstract

The analysis by HPLC-PDA of the hydroalcoholic extract of the leaves of M. eriocarpum together with the injection of the fractions containing the already identified metabolites allowed the detection of at least 5 flavonoids, of which two are derived from apigenin and three from luteolin. After isolating larger amounts of isovitexin (I), assays were performed to evaluate the allelopathic activity together with the crude extract. The results show that the initial inhibition indexes were very similar to those observed in the treatments with F17 (Fraction enriched in isovitexin) and F18 (isovitexin), mainly in the concentrations of 500 and 1000?mg L^?1. The index of the number of lateral roots, an increase of the inhibitory effect is observed with the increase of the concentration of M. eriocarpum extract.     

Synthesis of 1‐Arylethyl‐2‐arylethylamino‐5‐trifluoroacetyl‐1,2,3,4‐tetrahydropyridines and Related Compounds with Potential Cell Efflux Pump Inhibition

This study reports a simple, fast, and efficient method for the synthesis of a new series of 1‐arylethyl‐2‐arylethylamino‐5‐trifluoroacetyl‐1,2,3,4‐tetrahydropyridines and related compounds from the reaction of 2‐alkoxy‐5‐trifluoroacetyl‐3,4‐dihydro‐2H‐pyrans with 2‐arylethanamines and related 2‐ethanamines. The desired tetrahydropyridines were obtained in excellent yields (90–98%), through a reaction that can be described as an AAB′ three‐component reaction protocol following an ANRORC‐type mechanism.     

Microwave assisted regiospecific synthesis of 5‐trifluoromethyl‐4,5‐dihydropyrazoles and—pyrazoles

The regiospecific synthesis of a series of twelve 5‐trifluoromethyl‐4,5‐dihydropyrazoles and ‐pyrazoles from the cyclocondesation reaction of 4‐alkoxy‐1,1,1‐trifluoro‐3‐alken‐2‐ones [F₃CC(O)CH=C(R¹)OR, where R¹ = Me, Et, Pr, iso‐Pr, Bu, iso‐Bu, Ph, H; and R = Me, Et] with phenylhydrazine in toluene by environmentally benign microwave induced techniques is reported. It is shown that under appropriated conditions, the variation of microwave irradiation power leads to 4,5‐dihydropyrazole or pyrazole derivatives. This paper also includes the use of montmorillonite K‐10 as a solid support for the synthesis of pyrazoles under solvent free conditions.     

Haloacetylated enol ethers: 15. Study of the regiochemistry of the cyclo‐condensation of β‐alkoxyvinyl trihalomethyl ketones with N‐methyl thiourea

A study of the regiochemistry of the cyclo‐condensation reaction of ß‐alkoxyvinyl trihalomethyl ketones with an unsymmetric dinucleophile N‐methyl thiourea to afford a series of 1‐methyl‐3‐(4,4,4‐trifluoro[chloro]‐3‐oxo‐1‐butenyl)thioureas and the corresponding N‐methyl pyrimidinethione derivatives is reported. The absolute assignment of the position of the N‐methyl group in the pyrimidine ring was obtained through a nmr study based on two dimensional HMBC and NOESY experiments.     

On regularity of block triangular fuzzy matrices

Necessary and sufficient conditions are given for the regularity of block triangular fuzzy matrices. This leads to characterization of idempotency of a class of triangular Toeplitz matrices. As an application, the existence of group inverse of a block triangular fuzzy matrix is discussed. Equivalent conditions for a regular block triangular fuzzy matrix to be expressed as a sum of regular block fuzzy matrices is derived. Further, fuzzy relational equations consistency is studied.     

New succinyl‐spaced pyrazoles: Regioselective synthesis of 1,4‐bis[5‐(trichloromethyl)‐1H‐pyrazol‐1‐yl]butane‐1,4‐diones

The facile and convenient access by a conventional procedure in ethanol as solvent to a new series of succinyl‐spaced pyrazoles including 1,4‐bis[5‐(trichloromethyl)‐5‐hydroxy‐4,5‐dihydro‐1H‐pyrazol‐1‐yl]butane‐1,4‐diones (64–82%) and the respective dehydrated derivatives as 1,4‐bis[5‐(trichloromethyl)‐1H‐pyrazol‐1‐yl]butane‐1,4‐diones in 57–82% yields, from the regioselective cyclocondensation reactions of 4‐substituted 4‐methoxy‐1,1,1‐trichloroalk‐3‐en‐2‐ones with succinic acid dihydrazide, where the 4‐substituents are Me, Ph, 4‐FC₆H₄, 4‐ClC₆H₄, 4‐NO₂C₆H₄, 2‐furyl, and 2‐thienyl, is reported. J. Heterocyclic Chem., 2011.     

Regioselective synthesis and characterization of new 3‐aryl‐7‐trifluoromethyl‐[1,2,4]triazolo[4,3–a]pyrimidines

The regioselective synthesis and characterization of a new series of 3‐aryl‐7‐trifluoromethyl[1,2,4]triazolo[4,3–a]pyrimidines from the oxidative heterocyclization of 2‐(N′‐benzylidenehydrazino)‐4‐trifluoromethylpyrimidines with copper dichloride is described. J. Heterocyclic Chem., (2011).     

New one-pot, efficient, and regioselective method for the synthesis of 3-Trifluoromethyl-1H-1-phenylpyrazoles and alkyl 3-carboxylate analogs

An efficient and regioselective procedure for the synthesis of a series of alkyl(aryl/heteroaryl) substituted 3-trifluoromethyl-1H-1-phenylpyrazoles and alkyl 3-carboxylate analogs, from the cyclocondensation reactions of 4-alkoxy-1,1,1-trihaloalk-3-en-2-ones [CX₃C(O)CR²=CR¹(OMe/OEt), where R¹ = H, Me, Ph, 2-Furyl; R² = H; R¹-R² = -C₄H₈- and X = F, Cl] and 1-phenylsemicarbazide in an acidified alcoholic medium (R³OH/H₂SO₄), where R³ = Me, Et, Prⁱ was successfully applied and is described here in detail.     

Probabilistic Inductive Classes of Graphs

A unifying framework—probabilistic inductive classes of graphs (PICGs)—is defined by imposing a probability space on the rules and their left elements from the standard notion of inductive class of graphs. The rules can model the processes creating real-world social networks, such as spread of knowledge, dynamics of acquaintanceships or sexual contacts, and emergence of clusters. We demonstrate the characteristics of PICGs by casting some well-known models of growing networks in this framework. Results regarding expected size and order are derived. For PICG models of connected and 2-connected graphs order, size and asymptotic degree distribution are presented. The approaches used represent analytic alternative to computer simulation, which is mostly used to obtain the properties of evolving graphs.     

DAST promotes the synthesis of new 5-(trifluoromethyl)-3-(1,1-difluoroethan-2-yl)-1H-pyrazoles

This study describes, firstly, the synthesis of a new precursor, 4,6,6-trimethoxy-1,1,1-trifluorohex-3-en-2-one (1), from the trifluoroacetylation reaction of 1,1,3,3-tetramethoxybutane, in 65% yields. Afterwards, the reaction of 1 with two hydrazines (NH₂NHR, where R = 2-furanoyl, C₆F₅) led to a new series of 4,5-dihydro-1H-pyrazoles, containing an acetal-protected aldehyde function as substituent, in 90-97% yields. In a subsequent step, the dehydration reactions of these 4,5-dihydro-1H-pyrazoles gave the respective aromatic 1H-pyrazoles. Finally, we report the results of the deprotection reactions of the acetals to obtain the respective aldehyde function, as well as, the subsequent fluorination reaction using DAST, leading to new difluorinated derivatives in 55-60% yields.