Synthesis and Antioxidant Activity of Some New Binary Pyrazoles Containing Core Phenothiazine Moiety

α,β‐Unsaturated ketones containing phenothiazine moiety 4 , 5 , and 7 were synthesized by condensation of 2‐acetylphenothiazine ( 1 ) with different aryl aldehydes 2 , 3 and dimethylformamide dimethylaceal. Pyrazoles 11 , 18 , 20 , 22 , 23 , 24 , 25 , 26 , 28 , 29 , 31 , 32 and oxazole 34 skeletons were also synthesized by 1,3‐dipolar cycloaddition reactions of α,β‐unsaturated ketones with different nucleophilic reagents. Formylpyrazole derivative 36 was synthesized through Vilsmeier–Haack reaction of phenylhydrazone 35b . Newly synthesized compounds were screened for antioxidant activity. The data showed clearly that most of the compounds anchored to phenothiazine moiety displayed good antioxidant activity using ABTS method. Furthermore, compounds 11 , 14 , and 28 exhibited high protection against DNA damage induced by the bleomycin iron complex.     

Synthesis of 1‐Aryl‐1H‐indazoles via a Ligand‐Free Copper‐ Catalyzed Intramolecular Amination Reaction

A general synthesis of 1‐aryl‐1‐H‐indazoles from o‐halogenated aryl aldehydes or ketones and aryl hydrazines was described. This protocol included an intermolecular condensation and a ligand‐free copper‐catalyzed intramolecular Ullmann‐type coupling reaction. This method was applied to a wide range of substrates to produce the indazole products in good yields.     

Ligand‐free Pd/Cu‐catalyzed decarboxylative coupling of aryl iodides with α‐oxocarboxylates

This paper describes a palladium/copper‐catalyzed decarboxylative coupling of aryl iodides with α‐oxocarboxylates. The cross‐coupling reaction gives high chemical yields of aryl ketones and has wide functional group tolerance, making the transformation an attractive alternative to the traditional cross‐coupling approaches for aryl ketones. Copyright © 2014 John Wiley & Sons, Ltd.     

Regioselective synthesis of 1-alkyl- or 1-aryl-1H-indazoles via copper-catalyzed cyclizations of 2-haloarylcarbonylic compounds

[reaction: see text] A general method for the one-step regioselective synthesis of 1-alkyl- or 1-aryl-1H-indazoles from ortho-halogenated alkanoylphenones, benzophenones, and arylcarboxylic acids, via copper-catalyzed amination, was developed by using 0.2% mol of CuO in the presence of K(2)CO(3). The reaction involves amination followed by intramolecular dehydration. Different functionalized alkyl aryl ketones, diaryl ketones, and benzoic acid derivatives were efficiently coupled with several hydrazines. Ligands commonly employed as catalysts for intermolecular amination were shown to be ineffective for this cyclization.     

Palladium-catalyzed tandem reactions to form 1-vinyl-1h-isochromene derivatives

The palladium-catalyzed reaction of pinacolone with tert-butyldimethyl(3-(2-bromophenyl)allyloxy)silane results in direct formation of 1-vinyl-3-tert-butyl-1H-isochromene. This is the result of a ketone arylation followed by an intramolecular cyclization of the enolate with the allylic system. The use of a lithium diamide base appears to be essential for success. The tert-butyldimethylsilyl protecting group is also an essential choice as it furnishes the appropriate reactivity to promote allylic substitution after the aryl coupling process. The use of more effective leaving groups, such as acetate, results in reaction of the allylic group, and no aryl coupling is observed. Through the appropriate selection of phosphine ligand and solvent, either the cyclized isochromene product or the noncyclized intermediate may be formed selectively. A short combinatorial study of the scope and limitations of the reaction, involving 24 ketones, is described.     

A Simple and Efficient Procedure for the Preparation of Benzal Chlorides and Benzal Bromides

Benzal chlorides and benzal bromides were conveniently synthesized by reaction of aryl aldehydes with a Vilsmeier type reagent formed in situ by reduction of CC1₄ or CBr₄ in dimethylformamide (DMF) as solvent.     

Development of new synthetic methods with aryl 1-chlorovinyl sulfoxides

Aryl 1-chlorovinyl sulfoxides were easily synthesized from ketones and aldehydes with aryl chloromethyl sulfoxide in three-steps with high overall yields. Low-temperature treatment of the aryl 1-chlorovinyl sulfoxides with alkyllithium or a Grignard reagent gave alkylidene carbenoids via a sulfoxide-metal exchange reaction. From the alkylidene carbenoids, acetylenic compounds, tetra-substituted olefins, and allenes were synthesized. Enolization of alpha-chloro alpha-sulfinyl ketones, which were synthesized from methyl esters and chloromethyl phenyl sulfoxide, is another method for the generation of aryl 1-chloroalkyl sulfoxides. Treatment of 1-chlorovinyl phenyl sulfoxides so generated with t-BuLi followed by some nucleophiles having an acidic hydrogen gave one-carbon elongated carboxylic acids and their derivatives. Conjugate addition of some carbanions with 1-chlorovinyl p-tolyl sulfoxides was found to have taken place. For example, reaction of 1-chlorovinyl p-tolyl sulfoxides with cyanomethyllithium gave high yields of cyclic enaminonitriles. Acidic treatment of the enaminonitriles afforded good yields of 4,4-disubstituted 2-cyclopentenones. By using unsymmetrical ketones and optically pure chloromethyl p-tolyl sulfoxide, this procedure suggests a good method for an asymmetric synthesis of optically pure 4,4-disubstituted 2-cyclopentenones. This method achieved an asymmetric total synthesis of (+)-alpha-cuparenone starting from methyl 4-methylphenyl ketone and (R)-(-)-chloromethyl p-tolyl sulfoxide. A novel synthesis of 2,4,4-trisubstituted 2-cyclopentenones is also successful using cyanomethyllithium and its homologues. Conjugate addition of the lithium enolate of tert-butyl acetate and its homologues gave high yields of the adduct, 3,3-disubstituted esters. Synthesis of various kinds of carboxylic acids and their derivatives and lactones was realized from the adducts.     

Reaction of Tröger’s base analogues with Vilsmeier reagents

As part of a program aimed at introducing functionality onto the Tröger’s base framework post-synthesis, we investigated the formylation reaction of Tröger’s base analogues with Vilsmeier reagents. We found that rather than the anticipated reaction at the aryl rings, these compounds react with Vilsmeier reagents to afford compounds with a modified strap, whereby the apical methylene group is replaced by a methylene strap bearing an N,N-disubstituted amine.     

Synthesis of Aryl α,α-Difluoroalkyl Ketones as Potent Inhibitors of Cholesterol Esterase

Aryl α,α-difluoroalkyl ketones were synthesized from the reaction of ethyl α,α-difluoroacylate with aryl lithium at ?78°C or from the coupling of aryl iododifluoromethyl ketone with 1-alkene in the presence of tetcrakis(triphenylphosphine)palladium(0). These compounds were potent inhibitors of pancreatic cholesterol esterase with K_i values in the range 15 μM-20 nM.     

Direct asymmetric aldol reaction of aryl ketones with aryl aldehydes catalyzed by chiral BINOL-derived zincate catalyst

Direct asymmetric aldol reaction of aryl ketones with aryl aldehydes catalyzed by chiral metal complex is reported for the first time herein. Two novel semicrown chiral ligands 1a and 1b were synthesized from (S)- and (R)-BINOL, respectively, and then employed to catalyze the direct asymmetric aldol addition of aryl ketones to aryl aldehydes. Introduced with 2.0 equiv of diethylzinc, 1b had higher enantioselectivity than 1a. Up to 97% yield and up to 80% enantioselectivity were achieved.     

Synthesis of carbazoles related to carbazomycin,hyellazole and ellipticine.

Two synthetic routes to 1,2-disubstituted carbazoles are described. The first involves condensation of 2-alkyl-substituted indoles with 2,3-unsaturated ketones in the presence of Pd/C and molecular sieves, the second is based on the reaction of a 2-vinylic indole with the Vilsmeier reagent. The vinylic indoles were prepared by a Fischer indole synthesis, or via 1-benzenesulphonyl-2-lithioindole.     

Formylation of 3,4-Dihydropyrrolo[1,2-a]pyrazines

Formylation of 3,4-dihydropyrrolo[1,2-a]pyrazines containing alkyl or aryl substituents at position 1 has been studied under the conditions of the Vilsmeier reaction. The direction of the reaction depends on the structure of 3,4-dihydropyrrolo[1,2-a]pyrazine starting materials. Formylation of 1-methyl-substituted 3,4-dihydropyrrolo[1,2-a]pyrazines occurs at the methyl group.     

A Facile One‐Pot Synthesis of Chloropyridines from Chalcones

Malononitrile undergoes Michael addition to iminoalkylated chalcones under Vilsmeier–Haack reaction condition. In situ intramolecular cyclization followed by aromatization of the adduct resulted in the formation of 4,6‐bis(aryl)‐2‐chloropyridines in good yields.     

Metallation reactions. XXXIV. Synthesis of 2‐(1‐hydroxy‐1‐arylethyl)‐1,3‐benzoxathiol‐3‐oxide derivatives

The reaction of benzoxathiole‐3‐oxide with lithiumdiisopropylamide in tetrahydrofuran gave an anion, which was reacted with various aryl‐methyl‐ketones to give 2‐(1‐hydroxy‐1‐arylethyl)‐1,3‐benzoxathiol‐3‐oxide derivatives. The reaction was carried out in different temperature conditions: at ‐88 °C the trans addition stereoisomers to the sulfoxide oxygen atom were the main products.     

Nickel N‐Heterocyclic Carbene Catalyzed CC Bond Formation: A New Route to Aryl Ketones

A novel nickel N‐heterocyclic carbene catalyzed cross‐coupling reaction of aryl aldehydes with boronic esters for the synthesis of aryl ketones was developed. This reaction provides a mild, practical method toward aryl ketones, which are versatile intermediates and building blocks in organic synthesis.     

Gold catalysis: five new bonds by a domino hydroarylation/cycloisomerization

The gold-catalyzed reaction of furans possessing one unsubstituted 2-position with ethynyl vinyl ketones bearing alkyl groups on the alkene led to interesting phenols of the indan-1-one-type by a domino hydroarylation/cycloisomerization. The yields were moderate but higher than in longer routes described before. With ethynyl vinyl ketones that have an aryl substituent, the chemoselectivity of the reaction was different. Then products from an initial reaction at the ethynyl group were observed.     

Microwave-promoted cross-coupling of acid chlorides with arylboronic acids: a convenient method for preparing aromatic ketones

Simple catalytic systems for cross-coupling reactions of acyl chlorides with arylboronic acids under microwave conditions were tested. Microwave irradiation facilitated the reaction course. Mild reaction conditions afford the symmetrical and unsymmetrical aryl ketones in reasonable to high yields within a short time. A wide range of substrates bearing an electron-donating or an electron-withdrawing substituent on aryl ring of acid chloride as well as on boronic acid were examined and high yields of ketones were produced.     

Palladium-catalyzed synthesis of aryl ketones by coupling of aryl bromides with an acyl anion equivalent

Palladium-catalyzed couplings of aryl bromides with N-tert-butylhydrazones as acyl anion equivalents to form aryl ketones are reported. The coupling process occurs at the C-position of hydrazones to form N-tert-butyl azo compounds. Isomerization of these azo compounds to the corresponding hydrazones, followed by hydrolysis, gave the desired mixed alkyl aryl ketones. The selectivity of C- versus N-arylation was strongly influenced by the substituent on nitrogen. Arylation at carbon occurred with N-tert-butylhydrazones, whereas N-arylation occurred with N-arylhydrazones. The arylation of hydrazones containing primary and secondary alkyl groups, as well as aryl groups, gave the desired ketones in good yields after hydrolysis. Functional groups on the aromatic ring, such as alkoxy, cyano, trifluoromethyl, carboalkoxy, carbamoyl, and keto groups, were tolerated. This reaction likely occurs by C-C bond-forming reductive elimination from an intermediate containing an eta1-diazaallyl ligand.     

Synthesis and properties of z-1,3-bis-(aryl)-4-bromo-2-buten-1-ones

Bromination of 1,3-bis(aryl)-2-buten-1-ones by N-bromosuccinimide in anhydrous carbon tetrachloride gives Z-1,3-bis(aryl)-4-bromo-2-buten-1-ones. The effect of the nature of substituent in the benzene ring on the course of a reaction with nucleophiles has been studied. Heating an alcohol solution of these ketones (Ar = 4-MeOC₆H₄, 4-ClC₆H₄) in the presence of acid or in the presence of base (Ar = Ph) gave 2,4-bis(aryl)furans. Treatment of 1,3-bis(aryl)-4-bromo-2-buten-1-ones with thioacetamide gave 2,4-bis(aryl)thiophenes. The oxidation of the halo-substituted dypnones with H₂O₂/NaOH gave (3-bromomethyl-3-aryl-2-oxiranyl)(aryl)methanones. The reaction of halo-substituted dypnones with aryl hydrazines gave 1,3,5-triaryl-1,6-dihydropyridazines or 1,3,5-triarylpyridazinium bromides depending on the structure of the reagents.     

Catalytic [4+1] cycloaddition of alpha,beta-unsaturated carbonyl compounds with isocyanides

The GaCl(3)-catalyzed [4+1] cycloaddition reactions of alpha,beta-unsaturated ketones with isocyanides leading to lactone derivatives are described. While some other Lewis acids also show catalytic activity, GaCl(3) was the most efficient catalyst. The reaction is significantly affected by the structure of both the isocyanides and the alpha,beta-unsaturated ketones. Aromatic isocyanides, especially sterically demanding ones and those bearing an electron-withdrawing group, can be used, but aliphatic isocyanides cannot. The bulkiness of substituents at the beta-position of acyclic alpha,beta-unsaturated ketones is an important factor for the reaction to proceed efficiently. Generally, the more the bulky substituent, the higher is the yield. The reaction of alpha,beta-unsaturated ketones bearing geminal substituents at the beta-position gave the corresponding products in high yields. In monosubstituted derivatives, the yields are relatively low. However, substrates having a bulky substituent, such as a tert-Bu group, at the beta-position give high yields. Bulkiness is also required in cyclic alpha,beta-unsaturated ketones, but the effect is small. In alkyl vinyl ketones, the reactivity decreased with the steric bulk of the alkyl group. In aryl vinyl ketones, the presence of an electron-donating group on the aromatic ring decreases the reactivity. The success of the catalysis can be attributed to the low affinity of GaCl(3) toward heteroatoms, compared with usual Lewis acids.