Cu-assisted C–N bond formations in six-membered N-heterocycle synthesis

Abstract

One of the highly emerging and important aspect of organic chemistry is the metal-catalyzed synthesis of the heterocycles. The methodologies used earlier for its synthesis were less approachable to the organic chemist because of their high cost, highly specified instrumentation and inconvenient methods. For both the stereoselective and regioselective synthesis of six-membered nitrogen-containing heterocycles, cyclic reactions that are Cu-catalyzed have known to be very efficient. The presented review covers the varied applications of Cu as a catalyst and its importance in the formation of six-membered nitrogen-containing heterocycles. The fascinating research that has been done in this area is also enclosed in this review.     

Unlike surfactant–polymer interactions of sodium dodecyl sulfate and sodium dodecylbenzene sulfonate with water-soluble polymers

Single and mixed micelle formation by sodium dodecyl sulfate (SDS) and sodium dodecylbenzene sulfonate (SDBS) and their mixtures in pure water and in the presence of water-soluble polymers such as Synperonic 85 (triblock polymer, TBP), hydroxypropylcellulose (HPC), and carboxymethylcellulose sodium salt (CMC) were studied with the help of conductivity, pyrene fluorescence, cyclic voltammetry, and viscosity measurements. Conductivity measurements showed a single aggregation process for pure surfactants and their mixtures both in pure water as well as in the presence of water-soluble polymers. Triple breaks corresponding to two aggregation processes for SDS, SDBS, and their mixture in the presence of TBP were observed from fluorescence measurements. The first one demonstrated the critical aggregation process due to the adsorption of surfactant monomers on TBP macromolecule. The second one was attributed to the participation of surfactant–polymer aggregates formed at the first one, in the micelle formation process. The aggregation number ( N _agg) of single and mixed micelles and diffusion coefficient ( D) of electroactive probe were computed from the fluorescence and cyclic voltammetry measurements, respectively. Both parameters, along with the viscosity results, indicated stronger SDS–polymer interactions in comparison to SDBS–polymer interactions. Mixed surfactant–polymer interactions showed compensating effects of both pure surfactants. The nature of mixed micelles was found to be ideal in all cases, as evaluated by applying the regular solution and Motomura's approximations.     

Solid-phase fluorescent BODIPY–peptide synthesis via in situ dipyrrin construction

Traditional fluorescent peptide chemical syntheses hinge on the use of limited fluorescent/dye-taggable unnatural amino acids and entail multiple costly purifications. Here we describe a facile and efficient protocol for in situ construction of dipyrrins on the N-terminus with 20 natural and five unnatural amino acids and the lysine''s side chain of selected peptides/peptide drugs through Fmoc-based solid-phase peptide synthesis. The new strategy enables the direct formation of boron–dipyrromethene (BODIPY)–peptide conjugates from simple aldehyde and pyrrole derivatives without pre-functionalization, and only requires a single-time chromatographic purification at the final stage. As a model study, synthesized EBNA1-targeting BODIPY1–Pep4 demonstrates intact selectivity in vitro, responsive fluorescence enhancement, and higher light cytotoxicity due to the photo-generation of cytotoxic singlet oxygen. This work offers a novel practical synthetic platform for fluorescent peptides for multifaceted biomedical applications.

Solid-phase fluorescent BODIPY–peptide synthesis via in situ dipyrrin construction offers an efficient fluorescent peptide synthetic platform for multifaceted biomedical applications.     

Designing,antifungal and structure activity relationship studies of Azomethines and β-lactam derivatives of aza heterocyclic amines

The present investigation deals with the synthesis of seven azomethine derivatives 1–7 of aza heterocyclic amines by carrying out condensation reaction of them with veratraldehyde followed by cyclizing the CHN moiety in synthesized azomethines of 4-amino-1,2,4-triazole and 4-amino antipyrine to yield β lactam derivatives 8–9. The chemical constituents in the synthesized compounds were confirmed by UV, IR, 1H NMR, ¹³C NMR, and elemental analysis. In vitro antifungal activity of all the synthesized products was done against four pathogenic maize fungal strains i.e. Fusarium verticillioides, Macrophomina phaseolina, Rhizoctonia solani, and Dreschlera maydis. It was found that azomethine derivative having 4-amino-1,2,4-triazole ring was as effective as standard carbendazim 50 WP against R. solani and may be considered as promising antifungal agent; therefore further modifications may be done in its structure to get better drug candidate in future.     

[1,3]Dioxolo[5,6][1]benzothieno[2,3-c]-quinolin-6(5H)-ones

Summary The reaction of 3,4-methylenedioxycinnamic acid (1) with thionyl chloride resulted in the formation of 7-chlorothieno[2,3-f]-1,3-benzodioxole-6-carbonyl chloride (2) and cinnamoyl chloride (3). Subsequent reaction of the former withp-substituted anilines led to the formation of 7-chloro-N-(p-substituted phenyl)-thieno[2,3-f]-1,3-benzodioxole-6-carboxamides (4a–c) which on photocyclization afforded 2-substituted [1,3]dioxolo[5,6][1]benzothieno[2,3-c]quinolin-6(5H)-ones (5a–c) in fairly good yields and high purity. The structures have been confirmed by IR,¹H NMR, and analytical methods.Accepted for presentation at the Hong Kong International Symposium on Heterocyclic Chemistry (August 13–16, 1995)     

Kinetics and mechanism of the oxidation of DL-methionine bybis(2,2′-bipyridyl)copper(II) permanganate

Summary The oxidation ofDL-methionine (MT) bybis(2,2-bipyridyl)copper(II) permanganate (BBCP) to the corresponding sulphoxide is first order in BBCP. Michaelis-Menten-type kinetics were observed with respect to MT. The formation constant of the intermediate complex and the rate constant for its decomposition were evaluated. The thermodynamic and activation parameters were also evaluated. The reaction is catalysed by H⁺ but 2,2-bipyridine does not affect the reaction rate. A mechanism is proposed.     

Non-collective oblate states in119Te

High spin states of¹¹⁹Te, populated in¹¹⁰Pd(¹³C, 4n) and¹¹⁰Pd(¹²C, 3n) reactions, have been studied throughγ-ray spectroscopy. The level scheme has been established up to j^π=(55/2^?). Three-quasiparticle states, based onπg ₇ ^2/2 ?vh _11/2 andπg _7/2 d _5/2?vh _11/2 configurations, have been identified. A particularly favoured 39/2^? state is suggested to be the fully aligned [πg ₇ ^2/2 ]₆₊?[vh ₁₁ ^2/3 ]_27/2? yrast non-collective oblate configuration. This assignment is supported by Total Routhian Surface (TRS) calculations which also suggest a similar oblate assignment to states at 21/2^?, 23/2^? and 37/2^?.     

A new band in doubly-odd118I

High spin states in¹¹⁸I, populated through¹⁰⁵Pd(¹⁶O,p2n) and¹⁰⁶Pd(¹⁶O,p3n) reactions, have been investigated through -ray spectroscopy. A new rotational-like structure, showing energy staggering in odd-even spin states, has been identified. This band, probably based on g_7/2 vh_11/2 configuration, exhibits competing noncollective behaviour above I=20 state. Recent assignment of this band to¹¹⁸Cs has been ruled out.     

Synthetic Ionophores. 13. Pyridine-Diamide-Diester Receptors: Remarkable Effect of Amide Substituents on Molecular Organization and Ag(+) Selectivity

The N(Py).HN(amide) hydrogen bonding within the macrocyclic cavities in 9, 10, and 13 invokes their symmetrical electron-deficient structures ((1)H NMR) and consequently bind with water. This results in their poor ionophore characters. The steric requirement of methyl/benzyl substituents on amide N in 11 and 12 takes the substituents out of the cavity and thus positions the amide O toward the cavity ((1)H, (13)C NMR and X-ray analysis). This arrangement of two pyridine N and two amide O ((13)C NMR, IR) binding sites provides an appropriate environment for selective binding toward Ag(+) over Pb(2+), Tl(+), alkali, and alkaline earth cations. The increased spacer length in 14 leads to a lop-sided twist of pyridine rings (X-ray) and disturbs the above arrangement and leads to its poor binding character.     

Effect of temperature on the ML of Au doped(Zn,Cd)S mixed phosphors

In this paper the effect of temperature on the mechanoluminescence of Au doped phosphors of(Zn,Cd)S is described.It is found that the ML disappears beyond a particular temperature.The temperature dependence of ML intensity follows the relation I =I_T~O(1-TIT_C)~n,where I_T~O is a constant,n is the slop of log I_T versus log(1- TIT_C) plot which lies between 0.9 and 1.10,T_C is the temperature at which ML disappear.It is found that the ML intensity in(Zn,Cd)S:Au disappear at 600 K.