2-(Prenyloxymethyl)benzoyl (POMB) as a new temporary protecting group for alcohols

The 2-(prenyloxymethyl)benzoyl (POMB) group was introduced in high yields to hydroxyl functions using the crystalline reagent, 2-(prenyloxymethyl)benzoic acid, in the presence of dicyclohexylcarbodiimide (DCC) and 4-dimethylaminopyridine (DMAP). 2-(Prenyloxymethyl)benzoic acid is readily available, in two steps, from phthalide in 65% overall yield. The POMB group can be cleaved, in two steps, by treatment with 2,3-dichloro-5,6-dicyanoquinone (DDQ) followed by intramolecular lactonisation of the resulting hydroxy ester induced by a catalytic amount of Yb(OTf)₃·H₂O. The reaction conditions are compatible with the presence of a number of protecting groups such as isopropylidene, benzyl, acetyl, chloroacetyl, benzoyl, levulinoyl, Fmoc and Boc groups.     

Alkoxyacetyl (AAc) group as a useful linker for organic synthesis on poly(ethylene glycol) support

An alkoxyacetyl group (AAc) group was found to be an efficient linker for high-throughput synthesis of small molecules on a soluble polymer support. The linker allows high-yield loading of alcohols and phenols either by conventional carbodiimide-mediated esterification or transesterification using Yb(OTf)₃. Chemoselective cleavage to release small molecules is attained also by Yb(OTf)₃ or TMSCHN₂. The preparation, protocols for loading and releasing of small molecules, and an application to the Ugi four-component coupling reaction are reported.     

Urea as leaving group in the synthesis of 3-(tert-butyl)perhydro-1,5,3-dithiazepine

The new compound 3-(tert-butyl)perhydro-1,5,3-dithiazepine has been synthesised from 5-(tert-butyl)perhydro-1,3,5-triazin-2-one in 45% yield. In the reaction, urea acts as the leaving group being exchanged for the S-CH₂-CH₂-S fragment of the product.     

Migratory insertion of bis(diethylamino)phosphine group into the N–N bond in the reaction of substituted hydrazobenzene with (Et2N)2PCl

Oxidative dehydrogenation of 2-bromo-4-methylaniline with manganese(iv) oxide leads to the formation of (E)-1,2-bis(2-bromo-4-methylphenyl)diazene (1). The reaction of 1 with hydrazine hydrate gives the reduction product, 1,2-bis(2-bromo-4-methylphenyl)hydrazine (2). Compound 2 sequentially treated with methyllithium and two equivalents of (Et₂N)₂PCl in diethyl ether is converted to the diazadiphosphinine derivative. The reaction includes the following steps: 1) the phosphorylation of the nitrogen atom in the dilithium salt of hydrazo derivative 2, 2) the migratory insertion of (Et₂N)₂P group into the N–N bond, 3) phosphorylation of the second nitrogen atom, 4) arylation of the phosphorus in the (Et₂N)₂P group.

     

Selective reduction of the nitro group in the presence of the azoxy group. Synthesis of 2-(alkyl-NNO-azoxy)anilines

Tin(ii) chloride selectively reduces the aromatic nitro group to the amino group, the azoxy group remaining intact. This allows the preparation of 2-(R-NNO-azoxy)anilines from 2-(R-NNO-azoxy)nitrobenzenes bearing electron-donating or weak electron-withdrawing substituents (Me or Br) in the benzene ring and alkyl substituents at the distal N atom of the azoxy group. The presence of electron-withdrawing substituents at the azoxy group (for example, CO₂Et) leads to a change in the direction of the reaction resulting in selective reduction of the azoxy group to the hydrazo group.     

A one-dimensional barium(II) coordination polymer with a coordinated nitro group of 2-nitrobenzoate

The aqueous reaction of barium carbonate with 2-nitrobenzoic acid (2-nbaH) results in the formation of a one-dimensional coordination polymer, catena-poly[[hexa(aqua)dibarium(II)]bis[(μ ₂-2-nitrobenzoate-O,O,O-NO₂)(μ ₂-2-nitrobenzoate-O,O,O′)]] 1. On heating at 100°C compound 1 is dehydrated to anhydrous barium bis(2-nitrobenzoate) 2. The anhydrous compound can be re-hydrated to 1 on exposure to water vapour. Compounds 1 and 2 were characterized by elemental analysis, IR and UV-Vis spectra, DSC thermograms, weight loss studies and the structure of 1 was determined. 1 and 2 can be thermally decomposed to BaCO₃ by heating at 800°C. The polymer [[Ba(H₂O)₃]₂(μ ₂-2-nba-O,O,O-NO₂)₂ (μ ₂-2-nba-O,O,O′)₂] _n 1 crystallizes in the centrosymmetric triclinic space group Pī and all atoms are located in general positions. The polymeric structure is based on a dimeric unit and consists of three water molecules coordinated to a central Ba(II) and two unique 2-nitrobenzoate (2-nba) anions, one of which (μ ₂-2-nba-O,O,O-NO₂) functions as a tridentate ligand and is linked to a Ba(II) through the oxygen atom of the-NO₂ group and forms a monoatomic μ ₂-carboxylate bridge between two symmetry related Ba(II) ions with a Ba···Ba distance of 4·5726(14) ?. The second unique 2-nba anion (μ ₂-2-nba-O,O,O′) also functions as a tridentate ligand with the carboxylate oxygen atoms linked to a Ba(II) ion in a bidentate fashion and one of the carboxylate oxygen atoms forming a monoatomic bridge between two symmetry related Ba(II) ions resulting in a Ba···Ba separation of 4·5406(15) ?. These differing tridentate 2-nba ligands link {Ba(H₂O)₃} units into a one-dimensional polymeric chain extending along b axis. In the infinite chain each nine coordinated Ba(II) is bonded to three water molecules and further linked to six oxygen atoms of four different 2-nitrobenzoate anions with alternating pairs of Ba(II) ions in the chain bridged by a pair of (μ ₂-2-nba-O,O,O-NO₂) and (μ ₂-2-nba-O,O,O′) ligands resulting in alternating Ba···Ba distances of 4·5406(15) and 4·5726(14) ? across the chain. Dedicated to Prof. S. K. Paknikar on the occasion of his 73rd birthday.     

Interaction between peroxide ion and phenol group which are coordinated to the same iron(III) ion

We have prepared several new iron(III) complexes with ligands which contain a phenol group; these are tetradentate [(X-phpy)H, X and H(phpy) represent the substituents on the phenol ring and N,N-bis(2-pyridylmethyl)-N-(2-hydroxybenzyl)amine, respectively] and pentadentate ligands [(R-enph-X)H; R=ethyl(Et) or methyl(Me) derivative and H(Me-enph) denotes N,N-bis(2-pyridylmethyl)-N″-methyl-N″-(2″-hydroxyl-benzylamine)ethylenediamine] and have determined the crystal structures of Fe(phpy)Cl₂, Fe(5-NO₂-phpy)Cl₂, and Fe(Me-enph)ClPF₆, which are of a mononuclear six-coordinate iron(III) complex with coordination of one or two chloride ion(s). These compounds are highly colored (dark violet) due to the coordination of phenol group to an iron(III) atom. When hydrogen peroxide was added to the solution of the iron(III) complex, a color change occurs with bleaching of the violet color, indicating that oxidative degradation of the phenol moiety occurred in the ligand system. The bleaching of the violet color was also observed by the addition of t-butylhydroperoxide. The rate of the disappearance of the violet color is highly dependent on the substituent on the phenol ring; introduction of an electron-withdrawing group in the phenol ring decreases the rate of bleaching, suggesting that disappearance of the violet band should be due to a chemical reaction between the phenol group and a peroxide adduct of the iron(III) species with an η¹-coordination mode and that in this reaction the peroxide adduct acts as an electrophile towards phenol ring. The intramolecular interaction between the phenol moiety and an iron(III)-peroxide adduct may induce activation of the peroxide ion, and this was supported by several facts that the solution containing an iron(III) complex and hydrogen peroxide exhibits high activities for degradation of nucleosides and albumin.     

o-Nitrobenzoyl group as a new amino protecting group for peptide synthesis and the synthesis of some anthranilyl peptides

N (o-nitrobenzoyl)amino acids can be coupled with other amino acids using DCC and the resulting product on hydrogenation gives peptides, containing the anthranilyl group as —NH₂ end group. N (anthranilyl)amino acids or peptides can also be obtained by reaction of isatoic anhydride on amino acids or peptides. The anthranilyl end group is easily cleaved by metal (Cu⁺²) catalysed hydrolysis to give α-amino acid peptides and the insoluble copper(II) anthranilate.     

Diorgano-tellur-bis-(dialkylcarbamate) und -(dithiocarbamate)

Diorganyltellurium Bis-(dialkylcarbamates) and -(dithiocarbamates) Compounds of the type R₂Te(X₂CNR′₂)₂, with R ? C₆H₅, CH₃; R′ ? CH₃, C₂H₅, i-C₃H₇, c-C₆H₁₁, C₆H₅, and X ? S, are obtained by reaction of dimethyltellurium with tetraorganyl-thiuram-disulfides. Dimethyltellurium diiodide or diphenyltellurium dichloride react with sodium dithiocarbamates or with in situ prepared ammonium dithiocarbamates. Some compounds can be synthesized by reaction of diphenyltellurium oxide with amine in solutions of carbon disulfide. The synthesis of diphenyltellurium- and dimethyltellurium bis-(dimethylcarbamates) results from the interaction of diorganyltellurium diethanolate with dimethylammonium dimethylcarbamate. Decomposition reactions of the compounds in solid and solution are studied ¹H-NMR, ¹³C-NMR, and mass spectroscopically. Diorganyltellurium diethylen-bis-(N,N′-dimethyldithiocarbamates) are obtained by reaction of dimethyltellurium diiodide or diphenyltellurium dichloride and sodium ethylen-bis-(N,N′-dimethyldithiocarbamate) as polymeric products.     

Cycloaddition Reactions of (NSCl)3 with Organic Nitriles

Abstract

The six-membered ring system RCN(NSCl)₂ (R= ^tBu, CCl₃, Me₂N, Et₂N, ⁱPr₂N) can be prepared by a cycloaddition reaction of the free nitrile, RCN, with cyclo-(NSCl)₃ at mom temperature. This reaction is slow for R= ^tBu and CCl₃, but it can be accelerated by UV light. The six-membered rings are converted to five-membered rings RCN₂S₂ ⁺ Cl^- by thermolysis. By varying the conditions of the cycloaddition reaction, 1,3-(RCN)₂(NSCl)₂ (R= Me₂N, Et₂N) and 1,5- RCN(NSN)₂SCl can be obtained.     

Perhalogenmethylmercapto-heterocyclen,IX (perchlormethylmercapto)- und (perfluormethylmercapto)pyridine

Methods of substituting pyridine by perhalogenomethylmercapto groups are discussed. The side chain chlorination of 2-(methylmercapto)pyridine leads gradually to 2-(trichloromethylmercapto)pyridine hydrochloride ($\text{1a}$) and 2-(trichloromethylmercapto)pyridine ($\text{1b}$). Neither a direct reaction of pyridine with CF₃SCl nor the way over a Grignard reaction or a sulfenylcarboxylate lead to CF₃S-substituted products. Reactions of pyridine and bromopyridines with Hg(SCF₃)₂ yield 1:1-adducts ($\text{2a-d}$) only. Lithium tetrakis(1,2-dihydro-1-pyridyl)aluminate (LDPA) reacts with CF₃SCl to give 3-(trifluoromethylmercapto)pyridine ($\text{3}$); in addition a disubstituted product can be identified massspectroscopically. ¹H- and ¹⁹F-NMR-spectra are reported.     

Anthraquinon-2-ylethyl-1′,2′-diol (Aqe-diol) as a new photolabile protecting group for aldehydes and ketones

A new photolabile protecting group for aldehydes and ketones, 2-(1,2-dihydroxyethyl) anthraquinone (Aqe-diol) and four caged compounds have been prepared and their photochemistry investigated. Upon 350 nm light irradiation, the caged compounds 2a-d in CH₃CN–H₂O solution can efficiently release the carbonyl compounds (conversion rate 60–90%), and their uncaging quantum efficiencies were measured, ranging from 0.03 to 0.09. On the basis of HPLC analysis and quenching experiments, a mechanism of the uncaging reaction was suggested.     

Infrared spectra and methyl group properties in dicyclopentadienyldimethyl-titanium(IV), -zirconium(IV) and -hafnium(IV)

Infrared spectra are reported for CH₃-, CD₃- and CHD₂-substituted Cp₂MMe₂ (Cp = η⁵-C₅H₅, M = Ti, Zr, Hf) in CCl₄ solution. The isolated CH stretching frequencies, ν(^isCH), measured in the CHD₂ species are lower than any previously observed in methylmetal compounds and the methyl CH bonds in Cp₂HfMe₂ are predicted to be the longest and weakest such bonds yet to have been characterised by this method. The methyl groups in Cp₂ZrMe₂ and Cp₂HfMe₂ have all three CH bonds equal, but in Cp₂TiMe₂ each methyl group contains two strong CH bonds and one weak one. This may be the result of steric overcrowding effects around the relatively small titanium atom. The symmetric deformation δ_s(CH₃) rises with increasing atomic number of the metal atom, the reverse of the trend observed for methyl derivatives of Main Group elements.     

Spectroscopic,anti-bacterial,anti-cancer and molecular docking of Pd(II) and Pt(II) complexes with (E)-4-((dimethylamino)methyl)-2-((4,5-dimethylthiazol-2-yl)diazenyl)phenol ligand

New ligand (E)-4-((dimethylamino)methyl)-2-((4,5-dimethylthiazol-2-yl)diazenyl)phenol (HDmazo) was prepared by the coupling reaction between 4,5-dimethylthiazol-2-amine and 4-((dimethylamino)methyl)phenol. Moreover, the [MCl₂(HDmazo)] and [M(HDmazo)₂] [M^II = Pd and Pt] were prepared using the direct reaction of equivalent molar of HDmazo and Na₂PdCl₄ or K₂PtCl₄. The HDmazo and its complexes were investigated by different spectroscopic techniques. In complexes (1–2) HDmazo ligand behaves as bidentate style through the nitrogen of azo group and nitrogen of thiazole ring towards Pd(II) and Pt(II). Or in a bidentate fashion via the oxygen atom of the hydroxylate group and nitrogen atom of azo group as mono-anion in complexes (3–4). Further, the study of biological activity against four pathogenic bacteria showed that compound (3) exhibited good activity compared to other compounds. Additional the anti-tumor action against A2870 cell lines was screened, and the complexes (1) and (2) displayed good activity with 7.45 ± 0.98 µM and 13.23 ± 1.43 µM, respectively. The binding mechanism of the prepared compounds with EGFR tyrosine kinase, was investigated using molecular docking experiments.     

Synthesis of N-aminopyrazoles by Fe(II)-catalyzed rearrangement of 4-hydrazonomethyl-substituted isoxazoles

A novel effective method is reported for the preparation of 1-amino-1H-pyrazole-4-carboxylic acid derivatives by Fe(II)-catalyzed rearrangement of isoxazoles having (2,4-dinitrophenylhydrazono)methyl substituent at C4. The reaction proceeds smoothly for both E and Z isomers of 4-(hydrazonomethyl)isoxazoles, and this means it is not necessary to separate mixtures of E/Z-isomers of the hydrazones prepared by reaction of 5-methoxy/pirrolidino-4-carbonylisoxazoles and 2,4-dinitrophenylhydrazine. The rearrangement proceeds via the formation of an aziridine intermediate which can be isolated in certain cases. The 2-nitro group in the synthesized 1-[(2,4-dinitrophenyl)amino]-1H-pyrazole-4-carboxylic esters can be selectively reduced in two steps via acylation of the amino group followed by hydrogenation-deacylation using H₂-Pd/C.     

Reaktionen von Phosphorigsäure-bis(dimethylamid) und Phosphorsaäure-tris(methylamid) mit PCI3

Reactions of Phosphorous Bis(dimethylamide) and Phosphoric Tris(methylamide) with PCI₃ From the products of the reaction between phosphorous bis(dimethylamide) and PCl₃ in the presence of pyridine the pentakis(dimethylamide) of acid can be isolated. The reaction between phosphoric tris(methylamide) and PCl₃ in the presence of pyridine yields crystalline O = P[NCH³? PCl₂]₃ which can be converted into O = P[NCH³? PF₂]₃ with SbF₃ or AsF₃. The nmr data of the new compounds and some by-products of the reaction are given and discussed.     

Oxidative alkylamination of 2-methyl-3(2H)-cinnolinone: unexpected dealkylation of the entering alkylamino group

The oxidative alkylamination of 2-methyl-3(2H)-cinnolinone by secondary alkylamines in the presence of KMnO₄ leads to the smooth formation of the expected 4-alkylamino-2-methyl-3(2H)-cinnolinones. The analogous reaction with primary alkylamines is accompanied by the partial or complete N-dealkylation of the entering alkylamino group depending on the temperature. *Dedicated with gratitude to an outstanding heterocyclic chemist, Prof. Henk van der Plas on the occasion of his eightieth jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 602-611, April, 2009.     

SYNTHESIS AND CHARACTERIZATION OF PHTHALAZINONE POLY(ARYL ETHER SULFONE KETONE)WITH CARBONYL GROUP*

A kind of novel heat-resistant, high performance engineering thermoplastic phthalazinone poly(aryl ether sulfoneketone) (PPESK) containing a carboxyl group in its side chain was prepared by the nucleophilic displacement reaction of 4-(4-hydroxylphenyl)-1(2H)-phthalazinone with di(4-chlorophenyl) sulfone, 4,4'-difluoro-benzophenone and phenolphthalin insulfolane in the presence of K_2CO_3 to produce high molecular weight polymers which can be dissolved in some polarsolvents such as chloroform and nitrobenzene at room temperature and can be easily can into flexible, yellowish andtransparent films. PPESK is an amorphous polymer having a decomposition temperature above 400℃, which indicates that ithas high thermal stability. At the same time, the thermal properties of PPESKs with dicyandiamide (DICY) as curing agentindicated that the heat-resistance properties of the PPESKs are improved after curing. The apparent activation energy (ΔE) ofthe cross-linking reaction and the reaction order (n) of PPESK/DICY were found to be 52.2 kJ/mol and ca. 1.0, respectively.Therefore, the cross-linking reaction is approximately a first order reaction.     

Design of postmetallocene catalytic systems of arylimine type for olefi n polymerization: XV. Synthesis of (N-Aryl)salicylaldimine ligands containing a but-3-enyloxy group and their complexes with titanium(IV) dichloride

A series of (N-aryl)salicylaldimines was synthesized by the reaction of salicylaldehydes substituted in the positions 3 and 5 by bulky tert-butyl or α-cumyl groups with hydrochlorides of o-, m-, and p-(but-3-enyloxy) aniline in the presence of triethylamine. The obtained compounds formed by the reaction with TiCl₂(OPr-i)₂ complexes of titanium(IV) dichloride L₂TiCl₂.     

Lithium-silylindolide als Precursor für 1,2-, 1,3-Bis(silyl)indole und Bis(indol-1,3-yl)silane

Lithium-silylindolide as Precursor of 1,2-, 1,3-Bis(silyl)indoles and Bis(indole-1,3-yl)silane Lithium-indolide reacts with difluorosilanes (F₂SiR₂: R = CHMe₂ ( 1 ); CMe₃ ( 2 )) in a molar ratio 2 : 1 with formation of bis(indole-1-yl)silanes. The 1-(di-tert-butylfluorosilyl)-3-(fluorodiisopropylsilyl)indole ( 3 ) is obtained in the reaction 1-(di-tert-butylfluorosilyl)-3-lithium-indolide and F₂Si(CHMe₂)₂. In a molar ratio 2 : 1 the bis(1-di-tert-butylfluorosilyl-indole-3-yl)diisopropylsilane 4 is formed. As a byproduct bis(1-di-tert-butylfluorosilyl-indole-3-yl)dimethylmethane ( 5 ) is isolated. A cleavage of THF and the formation of (indole-1-yl)diisopropylvinyloxysilan ( 6 ) occurs in the reaction of 1-diisopropylfluorosilylindole with t-BuLi in THF. 1-(di-tert-butylfluorosilyl)indole reacts with n-BuLi/TMEDA accompanied by an 1,2-anionic silyl group migration to give the 2-(di-tert-butylfluorosilyl)-1-lithiumindolide 7 . Hydrolysis of 7 gives the 2-(di-tert-butylfluorosilyl)indole ( 8 ). In the reaction of 7 with F₂Si(CHMe₂)₂ the 1-(diisopropylfluorosilyl)-2-(di-tert-butylfluorosilyl)indole 9 is obtained. 1-n-Butyl-diisopropylsilylindole ( 10 ) is the product of the reaction of F₂Si(CHMe₂)₂, n-BuLi/TMEDA and indole at –70 °C. Lithium-indolide reacts with 3 to give the 1-(di-tert-butylfluorosilyl)indole-3-yl)(indole-1-yl)-diisopropylsilane ( 11 ), the first example of this class of substances. In the reaction of 1 , F₂SiMe₂, and t-BuLi in THF the 1-(diisopropyl(indole-1-yl)silyl)-3-dimethyl-(3.3-dimethylbutylsilyl)indole 12 is isolated. The crystal structures of 2 , 5 and 9 are discussed.