Thermal cyclization of N-[2-(2-propenyl)-1-naphthyl] ketenimines: intramolecular Diels-Alder reaction versus [1,5] hydrogen migration. Synthesis of dibenz[b,h]acridines and benzo[h]quinolines

The thermal treatment of N-(2-propenyl)-1-naphthylamines provided the expected aza-Claisen rearranged products, 2-(2-propenyl)-1-naphthylamines and benz[g]indoles, these last derived from an intramolecular hydroamination reaction on those primary products. The 2-(2-propenyl)-1-naphthylamines were converted into their triphenylphosphazene derivatives, which by aza-Wittig reaction with disubstituted ketenes yielded N-[2-(2-propenyl)-1-naphthyl] ketenimines. The heating of these ketenimines in boiling toluene induced their cyclization either via an intramolecular Diels-Alder reaction, to afford dibenz[b,h]acridines, or via [1,5] hydrogen migration from the sp³ carbon atom of the propenyl substituent to the central carbon atom of the ketenimine fragment, followed by a 6π electrocyclic ring closure, to give benzo[h]quinolines.     

Efficient rearrangement of epoxides catalyzed by a mixed-valent iron trifluoroacetate [Fe3O(O2CCF3)6(H2O)3]

The mixed-valent oxo-centered triiron(III, III, II) trifluoroacetate complex [Fe₂^IIIFe^IIO(O₂CCF₃)₆(H₂O)₃] was prepared by reacting anhydrous iron(III) chloride with boiling trifluoroacetic acid under nitrogen. The non-hygroscopic and readily available mixed-valent triiron trifluoroacetate complex was found to be an efficient catalyst for the regioselective rearrangement of epoxides. A number of carbonyl compounds formed via the rearrangement of epoxides could be obtained by a simple filtration of the reaction mixture through a short plug of silica gel.     

Reactions with heterocyclic amidines,VII: Synthesis of some new pyrazolo[1,5-c]-1,2,4-triazines,pyrazolo[1,5-a]-1,3,5-triazines and pyrazolo[1,5-a]pyrimidines

Diazotised 5-amino-3-methyl-4-phenyloyrazole (1) reacted with active methylene reagents and with -naphthol to yield the pyrazolo[1,5-c)-1,2,4-triazine derivatives2a-e and5. Compound1 reacted with benzoyl isothiocyanate and with phenyl isothiocyanate to yield the corresponding pyrazol-5-ylthiourea derivatives6a, b. 5a was converted into the thiourea derivative8 by the action of acids or alkalies. A synthesis of 2-methyl-3-phenyl-4,5,6,7-tetrahydropyrazolo[1,5-a]-pyrimidin-5-one from the reaction of -phenylacetoactonitrile (3-oxo-2-phenyl-butyric nitrile) and -cyanoethylhydrazine is reported.

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Reaktionen mit heterocyclischen Amidinen, VII: Synthese einiger neuer Pyrazolo[1,5-c]-1,2,4-triazine, Pyrazolo[1,5-a]-1,3,5-triazine und Pyrazolo[1,5-a]pyrimidine

Zusammenfassung Diazotiertes 5-Amino-3-methyl-4-phenylpyrazol (1) reagiert mit einer aktiven Methylenkomponente und -Naphthol zu den Pyrazolo[1,5-c]-1,2,4-triazin-Derivaten2a-e und5. 1 ergibt mit Benzoylisothiocyanat und Phenylisothiocyanat die entsprechenden Pyrazol-5-yl-thioharnstoffe6a, b. 5a wurde mittels Säure oder Base in das Thioharnstoffderivat8 umgewandelt. Es wird über eine Synthese von 2-Methyl-3-phenyl-4,5,6,7-tetrahydropyrazolo[1,5-a]-pyrimidin-5-on aus -Phenylacetoacetonitril (3-Oxo-2-phenyl-butyronitril) und -Cyanoethylhydrazin berichtet.

     

Synthesis of new 5-aza-isosteres of guanine—5-aminosubstituted 1,2,4-triazolo[1,5-a]-1,3,5-triazin-7-ones

The reaction of 4-amino-substituted 6-hydrazinyl-1,3,5-triazin-2(1H)-ones with orthoformate proceeds via the Dimroth-type rearrangement to give 5-amino-substituted 1,2,4-triazolo[1,5-a]-1,3,5-triazine-7-ones. IR, NMR and X-ray studies have shown that the only product of the reaction was the [1,5-a]-isomer as prototropic 3H- and 6H-tautomers.     

Reactions of cyclo-octatetraene and its derivatives—VII: Reactions of cyclo-octatetraene tetramer and of the dimer heptacyclo[8.6.0.02,6.03,9.07,15.08,12.011,16]hexadeca-4,13-diene

Supplementary evidence has been obtained for the formulation of the cyclo-octatetraene tetramer as 1. Thus tetracyano-ethylene gives a 2:1 adduct 7, and at ca 310° the tetramer fragments cleanly to afford the cyclo-octatetraene dimer 9. Additions to dimer 9 may be effected selectively at the 4,5-double bond, and occur in the exo-mode. The generation of tetrachlorobenzyne from 3,4,5,6-tetrachlorobenzenediazonium carboxylate in tetrahydrofuran results in the ether-ester 22.     

Synthesis of some new purine-related compounds: Regioselective one-pot synthesis of new tetrazolo[1,5-a]pyrimidine,pyrazolo[1,5-a]pyrimidine and pyrimido[1,6-a]pyrimidine derivatives

An easy and efficient route for the synthesis of some tetrazolo[1,5-a]-, pyrazolo[1,5-a]- and pyrimido[1,6-a] pyrimidine derivatives was described through the reaction of sodium salts of formyl ketones with 5-aminotetrazole, 5-aminopyrazole derivatives and 6-aminothiouracil, respectively. The antimicrobial screening of some derivatives of the prepared compounds has been achieved, and it exhibited a moderate activity against the tested microorganisms.     

Synthesis of new heterocyclic phenols: 8-Hydroxy-s-triazolo[1,5-c] and [4,3-c] pyrimidines

The unknown title phenols have been prepared by condensation of ethyl orthoformate with 5-benzyloxy-4-hydrazino-pyrimidine and subsequent hydrogenolysis of the protecting group.     

High temperature bromination. Part 22: Bromination of 1a,2,7,7a-tetrahydro-1H-cyclopropa[b]naphthalene

The high-temperature bromination of 1a,2,7,7a-tetrahydro-1H-cyclopropa[b]naphthalene and its carboethoxy derivative was studied. Reaction of the title compound with 1 mol of bromine in refluxing carbon tetrachloride resulted in the formation of ring-opening products. In the case of the carboethoxy derivative, bromination took place both regio- and stereospecifically at the benzylic positions, the cyclopropane ring did not undergo bond cleavage. A mechanism for the formation of the products and their dehydrobromination reactions is discussed.     

Effect of intramolecular hydrogen bond on the azide-tetrazole equilibrium of 5-(2′-hydroxyphenyl)tetrazolo[1,5-a]pyrimidine,-tetrazolo[1,5-c]pyrimidme, -tetrazolo[1,5-c]quinazoline,and 7-(2′-hydroxyphenyl)tetrazolo[1,5-c]pyrimidine

The intramolecular hydrogen bond between the phenolic hydroxyl and the pyrimidine nitrogen atom in the title compounds exerts a destabilizing effect on the tetrazole ring and shifts the azide-tetrazole equilibrium toward the azide form, especially in the case of tetrazolo[c]pyrimidine and -[c]quinazoline. It has been found that the introduction of a methoxy group into theortho-position of the phenyl fragment stabilizes the tetrazole tautomer more efficiently than introduction of this group into thepara-position.For preliminary communication, see Ref. l.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1494–1502, August, 1995.This work was carried out with financial support from Russian Foundation for Basic Research (Project No. 94-03-0836 la).     

A computational investigation on the sequential rearrangement mechanism of 2-allyl-2,4,5-hexatrienaldehyde involving [1,5]-hydrogen migration and 8pi-electrocyclization

The sequential rearrangement reaction mechanism of the 2-allyl-2,4,5-hexatrienaldehyde has been studied at the unrestricted Becke three-parameter hybrid functional combined with Lee-Yang-Parr correlation functional (UB3LYP)/6-31G**, Complete Active Space Self-Consistent Field (CAS (8,8))/6-31G**, Configuration Interaction with Single and Double Excitations (CISD)//UB3LYP/6-31G** and the second-order perturbation theory based on the CASSCF reference wave function (CASPT2)//CAS(8,8)/6-31G** levels. Two pathways have been found to be involved for this reaction. The first pathway includes four processes of the rotation of the C3--C4 single bond, the stepwise [2 + 2] cycloaddition, the [1,5]-hydrogen migration, and the ring opening isomerization, while the second pathway undergoes only two processes of the [1,5]-hydrogen migration and the 8pi-electrocyclization. The calculation results indicate that the second pathway is favorable, in good agreement with the recent experimental observation. The whole reaction is stepwise and strong exothermic.     

A new synthesis of thes-triazolo[1,5-a]pyridine ring system

Summary A novel and efficient synthesis ofs-triazolo[1,5-a]pyridines was elaborated by reacting 1,2-diaminopyridinium salts with aldehydes.Dedicated to Prof.F. Sauter on the occasion of his 65^th birthday     

Computational and cyclic voltammetry studies of high effective-molarity assisted reversible reductions of [4]- and [5]heli-viologens: Potential building blocks for new materials

Computational and cyclic voltammetry studies have been used to explore electrochemical reductions of three helically chiral homologues, 2²⁺, 3²⁺, and 4²⁺, of methyl viologen. Thermochemical-electrochemical cycles are used as frameworks to describe the reversible redox properties of these helically chiral viologens as novel reversible four-sided ECEC (Electron-transfer Chemical-reaction Electron-transfer Chemical-reaction) processes.     

One pot three component synthesis of spiro [indolo-3,10’-indeno[1,2-b]quinolin]-2,4,11’-triones as a new class of antifungal and antimicrobial agents

A simple and efficient three component procedure has been developed for the synthesis of highly substituted spiro[indolo-3,10'-indeno[1,2-b]quinolin]-2,4,11'-triones by one pot three component condensation of enaminones, isatin and indane-1,3-dione in ethanol:water (1:1) in presence of ceric ammonium nitrate (CAN) as catalyst. This method provides several advantages such as lesser reaction time, high yield of products and operational simplicity. The antimicrobial activity of some of the compounds has been investigated against six microbial strains, some of the tested compounds showed good antimicrobial activity.     

Synthesis and antitumor activity of some new pyrazolo[1,5-a] pyrimidines

New series of pyrazolo[1,5-a]pyrimidine derivatives 7a-i, 11a-c and Schiff bases 13a-c were synthesized and screened for their in vitro antitumor activity against three human carcinoma cell lines, namely colorectal carcinoma (HCT116), prostate adenocarcinoma (PC-3) and liver carcinoma (HepG-2) using MTT cytotoxicity assay at 100 μg/mL. Some of the tested compounds displayed good anticancer activities against HCT-116 and PC-3 cells. Whereas, compounds 7d and 11a showed better antitumor activity than the rest of the compounds against both cell lines. A structure-activity relationship (SAR) has been discussed and structures of the newly synthesized compounds were confirmed by different spectral data (MS, IR, ¹H NMR and ¹³C NMR) and elemental analysis.     

SnAr Reactions of 2,4-Diazidopyrido[3,2-d]pyrimidine and Azide-Tetrazole Equilibrium Studies of the Obtained 5-Substituted Tetrazolo[1,5-a]pyrido[2,3-e]pyrimidines

A straightforward method for the synthesis of 5-substituted tetrazolo[1,5-a]pyrido[2,3-e]pyrimidines from 2,4-diazidopyrido[3,2-d]pyrimidine in SnAr reactions with N-, O-, and S- nucleophiles has been developed. The various N- and S-substituted products were obtained with yields from 47% to 98%, but the substitution with O-nucleophiles gave lower yields (20–32%). Furthermore, the fused tetrazolo[1,5-a]pyrimidine derivatives can be regarded as 2-azidopyrimidines and functionalized in copper(I)-catalyzed azide-alkyne dipolar cycloaddition (CuAAC) and Staudinger reactions due to the presence of a sufficient concentration of the reactive azide tautomer in solution. In total, seven products were fully characterized by their single crystal X-ray studies, while five of them were representatives of the tetrazolo[1,5-a]pyrido[2,3-e]pyrimidine heterocyclic system. Equilibrium constants and thermodynamic values were determined using variable temperature ¹H NMR and are in agreement of favoring the tetrazole tautomeric form (ΔG₂₉₈ = −3.33 to −7.52 (kJ/mol), ΔH = −19.92 to −48.02 (kJ/mol) and ΔS = −43.74 to −143.27 (J/mol·K)). The key starting material 2,4-diazidopyrido[3,2-d]pyrimidine presents a high degree of tautomerization in different solvents.     

Synthesis of Nonsymmetric Dibenzoyldihydromonobenzotetraazacyclo[14]annulenes as Transition Metal Hosts: X-ray Structure of 13,14-Benzo-3,10-di(p-chlorobenzoyl)-5, 8-dihydro-2,4,9,11-tetramethyl-1,5,8,12-tetraazacyclotetradeca-1,3,9,11-tetraene

In this paper, we evaluated the behavior of fibrous cerium (IV) acid phosphate (CeP) in insertion procedures involving a strong Lewis base (ethylamine) and a weak one (ɛ-caprolactam). In the former case, the procedure was performed by exposing a sample of CeP to a saturated amine atmosphere. Insertion was shown to be independent of the crystallinity of CeP, and the products showed strong host–guest interactions of the Coulombic type. Conversely, ɛ-caprolactam insertion was achieved by immersing CeP samples into its fused form. This process was dependent on the crystallinity of the inorganic solid, and host–guest interactions were characterized as involving hydrogen bonds.     

Synthesis of a 1,2,3-triazolo[1,5-a]-1,3,5-triazine. A new heterocyclic system

The synthesis of 3-methyl-7-oxo-5-thioxo-4H,6H-1,2,3-triazolo[1,5-a]-1,3,5- triazine (a new bicyclic system) is described. The key step involves reaction of 4-amino-5-methyl-1,2,3-triazole with carbethoxyisothiocyanate followed by cyclization with alkali.