Synthesis and Transformations of 4-Phosphorylated 2-Alkyl(aryl)-5-hydrazinooxazoles

Treatment of 1-phosphorylated 2,2-dichloroethenylcarboxamides with excess hydrazine hydrate gives in high yields phosphorylated derivatives of 2-alkyl(aryl)-5-hydrazinooxazoles containing the P(O)(OCH₃)₂, P(O)(OC₂H₅)₂, and P⁺(C₆H₅)₃ClO₄ ^- groups in the 4-position of the ring. The presence of the hydrazine group in these oxazole derivatives was confirmed not only by the spectral data, but also by the reactions with p-toluic aldehyde, p-toluic chloride, and phenyl isothiocyanate.     

Polyfuryl(aryl)alkanes and their derivatives

The reduction of 2-nitrophenyldifurylmethane with SnCl₂ leads to an indolenyl ketone as a result of intramolecular heterocycloaddition of the intermediately formed nitroso derivative. During the reduction of 2-nitroaryldifurylmethanes in the Zn+HCl or NH₂NH₂·H₂O+Pd/C systems, 2-aminoaryldifurylmethanes are formed; when treated with trityl perchlorate, their acetyl derivatives are converted into indolo[2,3-h]-1-oxazulenium perchlorates.For Communication 14, see [1].Kubansk State Technological University, Krasnodar. Severo-Osetinsk State University, Vladikavkaz. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1614–1621, December,1997.     

Unusual redox play of Mo(V/IV) during oxidative aryl–aryl coupling

The oxidative treatment of a suitable 1,3-diarylpropene precursor by MoCl₅ causes a series of redox steps yielding a dimer of dibenzo[a,c]cycloheptene. After the oxidative aryl–aryl bond formation, a C,H activation occurs providing a tropylium intermediate. Upon aqueous workup the metal waste acts as reductive media generating the dimer in an almost quantitative manner. The oxidative generation of the tropylium species as well as the subsequent redox play by the metal waste is unique and unprecedented. The dimeric compound can be oxidatively cleaved and subsequently decarboxylated providing the key intermediate of a previous synthesis of metasequirin-B derivatives.     

Palladium-catalyzed direct ortho-alkynylation of aryl acetamides with low catalyst loading

The palladium-catalyzed alkynylation of phenylacetic acid derivatives using 4-CF₃C₆F₄NH₂ as the auxiliary is described. The reaction efficiency can be greatly promoted by pyridine ligand, which enables the reaction to proceed at a catalyst loading as low as 1 mol%. Various functional groups are tolerated under the reaction conditions. The kinetic studies show that the rate of the reaction is first order in phenylacetamide and the Pd(OAc)₂ in combination of the pyridine ligand provides a highly robust and effective catalyst.     

Ruthenium-catalyzed coupling reaction of 2,3,5-trisubstituted furans with aryl halides through C-H bond cleavages

A variety of functionalized furans were synthesized by way of a ruthenium-catalyzed coupling reaction of 2,3,5-trisubstituted furans with aryl halides through C-H bond cleavages. The feature of the reaction was facilitative preparation of furan derivatives good functional group tolerance. All reactions gave the desired products in moderate to good yields (56-89%) in the presences of [RuCl₂(p-cymene)] and K₂CO₃ in NMP at 120 °C.     

Carbamic acid 2-trimethylsilylethyl ester as a new ammonia equivalent for palladium-catalyzed amination of aryl halides

Carbamic acid 2-trimethylsilylethyl ester (Teoc-NH₂) serves as an ammonia equivalent in the palladium-catalyzed amination of aryl bromides and aryl chlorides. Anilines with sensitive functional groups can be readily prepared using these amine derivatives.     

Synthesis and antifungal property of N-(aryl) and quaternary N-(aryl) chitosan derivatives against Botrytis cinerea

A series of N-(aryl) and their quaternary N-(aryl) chitosan derivatives were synthesized and evaluated for their antifungal activity against crop-threatening fungus Botrytis cinerea. Schiff bases were firstly synthesized by the reaction of chitosan with cinnamaldehyde, cuminaldehyde and 4-dimethylaminobenzaldehyde followed by reduction with sodium borohydride to form N-(aryl) chitosans. Quaternary N-(aryl) chitosans were then obtained by reaction of N-(aryl) chitosan compounds with ethyl iodide. The chemical structures were characterized by ¹H-NMR, FT-IR and UV spectroscopic techniques. The antifungal activity was evaluated in vitro against B. cinerea by mycelial growth inhibition method and in vivo by application of compounds to tomato plants prior to inoculation with fungal spores. In an in vitro experiment, all quaternized chitosans were more active than N-(aryl) chitosan derivatives and N,N,N-(diethylcinnamyl) chitosan (QC1) was the most potent (EC₅₀ = 1,147 mg/L) against mecelia however, N,N,N-(diethyl-p-dimethylaminobenzyl) chitosan (QC3) was the most potent (EC₅₀ = 334 mg/L) against spores. In an in vivo study, no disease incidence (0.0 %) was observed with QC1 and QC3 at 1,000 mg/L. Spray liquid chitosan enhanced total phenolics and guaiacol peroxidase in inoculated leaves.     

Cationic iridium-BINAP complex-catalyzed addition of aryl ketones to alkynes and alkenes via directed C-H bond cleavage

Cationic Ir complex ([Ir(cod)₂]BF₄ + BINAP) catalyzed the addition of ortho-C-H bonds in aryl ketones to alkynes, which gave alkenylated products in good to high yield. Styrene derivatives were good substrates, and the enantioselective addition to norbornene was also described.     

Highly efficient CuOx/OMS-2 catalyst for synthesis of phenoxathiin derivatives via intramolecular arylations of phenols with aryl halides

Phenoxathiin and its derivatives have attracted a great deal of interest due to their unique chemical and physical properties and their applications in fluorescent materials, antifungal activities and selective inhibitors. In the presence of copper supported on manganese oxide-based octahedral molecular sieves OMS-2 (CuO_x/OMS-2), the heterogeneously catalytic synthesis of phenoxathiinan derivatives via intramolecular arylations of phenols with aryl bromide or aryl chloride has been achieved. TEM and XRD have confirmed the CuO_x/OMS-2 catalyst has been successfully reused 8 times without a significant decrease in the yield, with simple filtration and washing as a means of separation.     

Ligand free palladium catalyzed decarboxylative cross-coupling of aryl halides with oxalate monoester salts

Ligand free Pd-catalyzed decarboxylative cross-coupling of potassium oxalate monoester and derivatives with aryl iodides and bromides is described. Functionalized aromatic esters can be efficiently synthesized via this method with only 1.0 mol % Pd(OAc)₂ catalyst without any phosphine ligand. This method illustrates an inexpensive and operationally simple method for the preparation of aromatic esters and acids, which is especially beneficial for a large scale synthesis.     

Selective synthesis of (E)-triethyl(2-arylethenyl)silane derivatives by reaction of aryl bromides with triethyl vinylsilane catalysed by a palladium-tetraphosphine complex

Cis, cis, cis-1,2,3,4-tetrakis(diphenylphosphinomethyl)cyclopentane / 0.5 [PdCl(C₃H₅)]₂ system catalyses the Heck reaction of vinylsilane derivatives with a range of aryl bromides with high ratio substrate/catalyst in good yields. The formation of mixtures of styrene, (E)-triethyl(2-arylethenyl)silane and triethyl(1-arylethenyl)silane derivatives was observed in some cases. Very high selectivities (up to 100%) in favour of the formation of (E)-triethyl(2-arylethenyl)silane derivatives were obtained in the presence of sodium acetate as base. With other bases such as potassium carbonate, the formation of large amounts of styrene derivatives was observed. The reaction tolerates several functions such as fluoro, trifluoromethyl, methoxy, dimethylamino, acetyl, formyl, benzoyl, carboxylate, nitro or nitrile. Moreover, turnover numbers up to 10,000 can be obtained for this reaction.     

Photopolymerization studies of alkyl and aryl ester derivatives of ethyl α-hydroxymethylacrylate

Several new benzoate ester derivatives of ethyl α-hydroxymethylacrylate were synthesized using phase transfer catalysis and found to display unexpectedly rapid photopolymerization; i.e., from 2 to 8 times faster than MMA. New derivatives described here include the 4-fluoro-, 4-trifluoromethyl-, 4-methyl-, 2-hydroxy-, 4-nitro-, 4-methoxy-, 4-cyano-, and 3,4,5-trimethoxybenzoate esters along with the parent benzoate ester. Relative reactivities of these monomers in photopolymerizations were compared with those of the nonaromatic formate, acetate, hexanoate, and stearate derivatives. Reactivities of the nonaromatic ester derivatives increased with the length of the side chain while for the more reactive aromatic esters, rates increased in the order 4-methyl-, 4-fluoro- and benzoate < 4-trifluoromethyl- and 2-hydroxy- < 4-cyano- < 4-methoxy- < 3,4,5-trimethoxybenzoate. T_gs of the benzoate polymers ranged from 125°C for the 4-fluoro to 163°C for the 4-cyanobenzoate while those of the alkyl ester derivatives ranged from 15 to 78°C. Number average molecular weights of photoinitiated polymers (ca 10,000–20,000) were lower than those found for bulk and solution polymers (20,000—708,000) consistent with higher radical concentrations from photoinitiation. These materials greatly expand the number of candidates available for rapid photocure in thin film and coating applications, especially because their physical properties are those of linear rather than highly crosslinked structures formed from multifunctional systems. © 1996 John Wiley & Sons, Inc.     

Efficient halogen-lithium exchange reactions to functionalize poly(alkyl aryl ether) dendrimers

Poly(alkyl aryl ether) dendrimers were functionalized with bromophenyl groups at their peripheries, so as to have 3, 6, 12, and 24 groups in the zero, first, second, and third generation dendrimers, respectively. The new bromophenyl functionalized dendrimers were assessed for their reactivities in C-heteroatom and C-C bond forming reactions. For this purpose, the bromophenyl functionalized dendrimers were converted quantitatively to their polylithiated derivatives, using n-BuLi in benzene. The polylithiated dendrimers were reacted either with D₂O or with CO₂, so as to afford the corresponding deuterated and carboxylic acid functionalized dendrimers, respectively. The carboxylic acid functionalized dendrimers were modified further to the methyl esters during their characterization.     

2-(Trimethylsilyl)ethanesulfonyl amide as a new ammonia equivalent for palladium-catalyzed amination of aryl halides

2-(Trimethylsilyl)ethanesulfonyl amide (SES-NH₂) is an ammonia equivalent for the palladium-catalyzed amination of aryl bromides and aryl chlorides. Using these amine derivatives, it has been observed that anilines and anilines with sensitive functional groups can be readily prepared.     

Preparation of methyl/benzyl(2-hydroxynaphthalen-1-yl)(aryl)methylcarbamate derivatives using magnesium hydrogen sulfate

A new approach to the synthesis of methyl/benzyl(2-hydroxynaphthalen-1-yl)(aryl)methylcarbamate derivatives based on the reaction of aldehydes, 2-naphthol and methyl/benzyl carbamate, using a catalytic amount of magnesium hydrogen sulfate [Mg(HSO₄)₂] as an efficient heterogeneous catalyst under solvent-free conditions has been developed.     

Synthesis of 3-[(aryl)-1,2,4-oxadiazol-5-yl]propionic acids

Seven 3,5-disubstituted oxadiazole derivatives, 3a-g , have been prepared by direct condensation of appropriate benzamidoxime with succinic anhydride. Spectroscopic properties, especially uv, ir and mass spectra confirmed the cyclic 1,2,4-oxadiazole structure. No ring-opened intermediate or side product could be observed. The ¹H-nmr assignments of the two CH₂ groups were unequivocally made by acid- and base-induced shifts.     

Highly substituted 2,3,7,8,12,13,17,18-octaethylporphyrins with meso aryl residues

Highly substituted porphyrin-bearing meso aryl groups are useful compounds for optical applications and for studies on the interrelationship between the substituent pattern, macrocycle conformation and physical properties. They serve as biomimetic models for the function of tetrapyrroles in nature and help to elucidate modulation of cofactor properties through conformational effects. Using a sequence of lithium organic substitution reactions the synthesis of novel free base 5,10-A₂- and 5,10-AB-2,3,7,8,12,13,17,18-octaethylporphyrins bearing donating groups such as -OMe and -NMe₂ on the aryl-substituent was achieved. Larger aromatic residues (1-naphthyl, 9-anthracenyl and 9-phenanthrenyl) could be introduced into the macrocycle system as well, and these systems were used for the preparation of highly substituted porphyrins with a mixed substituent pattern. Using phenanthrenyl derivatives, the complete series of meso phenanthrenyl substituted octaethylporphyrins was successfully synthesized and the palladium complexes were prepared for photophysical investigations. Structural studies clearly showed the influence of individual substituents on the conformation of the tetrapyrrole macrocycle and conformational analyses revealed the variation of the underlying distortion modes depending on the type and arrangement of the meso substituents.     

Iron/copper co-catalyzed highly selective arylation of sulfinamides with aryl iodides

In the present study, an inexpensive but efficient Iron(III) and Copper(II) co-catalyst without ligands catalyzed arylation of sulfinamides with aryl iodide was primarily reported. In brief, in the presence of Fe(NO₃)₃·9H₂O, CuO and K₃PO₄, the highly selective C–N cross coupling of several sulfinamides and aryl iodides was achieved in high chemical yield, while the aryl chlorides and bromides could not yield coupling products. It is noteworthy that through the arylation of chiral tert-butanesulfinamide with aryl iodides, N-aryl tert-butanesulfinamides are provided without racemization, even in gram-scale. The possible mechanism was that This oxidative addition process between copper catalyst and aryl-iodides might be significantly accelerated by active Fe(III) species. Moreover, using this synthetic method, a facile and efficient access was developed for the derivatives of N-phenyl sulfinamides, which might help to develop new drug molecules and material chemicals.     

Triorganotin aryl selenides

The SnSe bond in trimethyltin aryl selenides is cleaved on reaction with selenenyl halides, sulphenyl halides, alkyl halides and allyl halides. Thus Me₃SnSePh reacts with PhSeCl, 4-Me-2-NO₂C₆H₃SCl, RI (R = CH₃ or Ph₃SnCH₂) and CH₂CHCH₂Br to give PhSeSePh, 4-Me-2-NO₂C₆H₃SSePh, RSePh and CH₂CHCH₂SePh, respectively. The diselenide, PhSeSePh, is also obtained from Me₃SnSePh on reaction with either 4-MeC₆H₄SO₂Cl or NaIO₄. Exchange reactions also occur between Me₃SnSePh and Ph₃SnCl or PhHgCl.