One‐pot synthesis of aryl and heteroaroyl‐substituted hydroxypyrazolines from the reactions of β‐alkoxyvinyl trichloromethyl ketones with heteroarylhydrazides

The one‐step regiospecific synthesis of a novel series of 10 trichloromethyl‐, aryl‐, and heteroaroyl‐substituted 5‐hydroxy‐2‐pyrazolines affords 1‐(2‐thenoyl)‐, 1‐(2‐furoyl)‐, and 1‐(isonicotinoyl)‐3‐aryl‐5‐hydroxy‐5‐trichloromethyl‐4,5‐dihydro‐1H‐pyrazoles in 63–92% yields from the cyclocondensation reactions of 1,1,1‐trichloro‐4‐methoxy‐4‐aryl‐3‐buten‐2‐ones (where aryl substituents are –C₆H₅, 4‐CH₃C₆H₄, 4‐OCH₃C₆H₄, 4‐FC₆H₄, 4‐ClC₆H₄, 4‐BrC₆H₄) with 2‐thiophenecarboxylic hydrazide, furoic hydrazide, and isonicotinic acid hydrazide, respectively. Dehydration reaction of two 2‐pyrazolines with P₂O₅ furnished the corresponding 1H‐pyrazoles in low yields (21–29%). © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:685–691, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20261     

Synthesis of novel 5‐aryl‐1H‐tetrazoles

In this study phenylselenocyanate and some of its derivatives (o‐Cl, p‐Cl, p‐Br, o‐NO₂, p‐NO₂, o‐CH₃, p‐CH₃, o‐COOH, p‐COOH, p‐OCH₃ substituted) were synthesized ( 3a–3j ). The synthesized compounds were converted to 5‐aryl‐1H‐tetrazole ( 4a–4j ), by Et₃N ċ HCl‐NaN₃ in toluene, which are a new series of phenylselanyl‐1H‐tetrazoles. The structure of all the presently synthesized compounds were confirmed using spectroscopic methods (FTIR, ¹H NMR, MS). © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:255–258, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20293     

Unexpected regioselectivity in the palladium‐catalyzed reaction of silacyclobutanes with aryl iodides

The reaction of aryl iodides with 1,1‐diphenyl‐silacyclobutane in the presence of a catalytic amount of Pd(PPh₃)₄ affords unexpected ring‐opening adducts, 1‐ and 2‐propenyl(triaryl)‐silanes, in good yields. On the other hand, the PdCl₂(PhCN)₂‐catalyzed reaction of 1,1‐diphenylsilacyclobutanes with aryl halides gives ­unexpected products, triarylsilanols, after ­hydrolysis in moderate yields. The catalysis involves the reaction of aryl–palladium intermediates with silacyclobutanes along with ­regioselective aryl–silicon bond formation. Copyright © 2001 John Wiley & Sons, Ltd.     

Heck reactions of aryl halides with alk‐1‐en‐3‐ol derivatives catalysed by a tetraphosphine–palladium complex

cis,cis,cis‐1,2,3,4‐Tetrakis(diphenylphosphinomethyl)cyclopentane–[PdCl(C₃H₅)]₂ efficiently catalyses the Heck reaction of alk‐1‐en‐3‐ol with a variety of aryl halides. In the presence of hex‐1‐en‐3‐ol or oct‐1‐en‐3‐ol, the β‐arylated carbonyl compounds were selectively obtained. Turnover numbers up to 84 000 can be obtained for this reaction. Linalool and 2‐methylbut‐3‐en‐2‐ol led regio‐ and stereoselectively to the corresponding (E)‐1‐arylalk‐1‐en‐3‐ol derivatives. A minor electronic effect of the substituents of the aryl bromide was observed. Quite similar reaction rates were generally observed in the presence of activated aryl bromides such as bromoacetophenone and deactivated aryl bromides such as bromoanisole, indicating that, with these alkenols and this catalyst, the oxidative addition of aryl bromides to palladium is not the rate‐limiting step. It should be noted that this reaction also proceeds with sterically very congested aryl bromides such as 9‐bromoanthracene or 2,4,6‐triisopropylbromobenzene or with a vinyl bromide. On the other hand, low yields were obtained with aryl chlorides. Copyright © 2006 John Wiley & Sons, Ltd.     

Benzimidazolin‐2‐ylidene–palladium‐catalysed coupling reactions of aryl halides

The in situ prepared three‐component system Pd(OAc)₂–1,3‐dialkylbenzimidazolium chlorides ( 2a – f ) and Cs₂CO₃ catalyses, quantitatively, the Suzuki cross‐coupling of deactivated aryl chlorides and Heck coupling reactions of aryl bromide and iodide substrates. The 1,3‐dialkylbenzimidazolium salts ( 2a – f ) were characterized by conventional spectroscopic methods and elemental analysis. Copyright © 2005 John Wiley & Sons, Ltd.     

Photolytic transformation of aryl benzobisoxazole and aryl benzobisthiazole compounds into carbon dioxide

Solid‐state aryl benzobisoxazole and aryl benzobisthiazole compounds photolyzed in the presence of O₂ undergo cleavage to produce benzobisoxazoles (or benzobisthiazoles), benzonitriles, and benzamides. A very high percentage of the carbon atoms in one of the two segments from chain cleavage are converted to CO₂. This very unusual observation has been carefully confirmed by gas chromatography/mass spectroscopy analysis of the gaseous components in the photolysis vessel before and after photolysis, labeling experiments, and the correlation of the mass reduction in photolyzed polymers and the amount of CO₂ that evolves. The rate of CO₂ generation is used to compare the relative photostability of aryl benzobisoxazole and aryl benzobisthiazole model compounds, films, and fibers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1868–1877, 2007     

Efficient cyanation of aryl halide with K4[Fe(CN)6]⋅3H2O catalyzed by a P–O bidentate chelate palladium complex under air

Cyanation of aryl halide with K₄[Fe(CN)₆]?3H₂O has been carried out in the presence of a high‐activity catalyst: an air‐stable P–O bidentate chelate palladium complex. This method is applicable to both activated and deactivated aryl halides, and even a variety of aromatic nitriles are obtained in good yields under aerobic conditions. Copyright © 2014 John Wiley & Sons, Ltd.     

Synthesis of novel N‐alkyl/aryl‐N′‐(4‐arylthiazol‐2‐yl)‐N″‐xylosyl guanidines

The reaction of 2,3,4‐tri‐O‐acetyl‐β‐D‐xylopyranosyl isothiocyanate ( 1 ) and 2‐amino‐4‐arylthiazoles ( 2 ) gave xylosylthioureas 3 . These thiourea derivatives reacted with alkyl/aryl amine in the presence of HgCl₂ to give a new series of N‐alkyl/aryl‐N″‐(4‐arylthiazol‐2‐yl)‐N″‐xylosyl guanidines 4 . Some of the synthesized guanidines were screened for their biological activity. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:688–694, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20379     

Palladium‐catalysed Suzuki reaction of aryl chlorides in aqueous media using 1,3‐dialkylimidazolidin‐2‐ylidene ligands

A highly effective, easy to handle and environmentally benign process for palladium‐mediated Suzuki cross‐coupling is developed. The in situ prepared three‐component system Pd(OAc)₂–1,3‐bis(alkyl)imidazolinium chlorides (2a–f) and Cs₂CO₃ catalyses quantitatively the Suzuki cross‐coupling of deactivated aryl chlorides. Copyright © 2005 John Wiley & Sons, Ltd.     

Thiophene‐2,5‐dicarboxylic acid bis‐aryl(alkyl) amides

A base‐catalyzed condensation of diacetamido sulfides [(RNHCOCH₂)₂S)] with glyoxal affording thiophene‐2,5‐dicarboxylic acid bis‐aryl(alkyl)amides has been accomplished under mild conditions. Excellent results were readily obtained when R was a substituted 3‐nitrophenyl, 4‐nitrophenyl, 4‐chlorophenyl group, but the yield was poor when R was cyclohexyl. Unknown compounds were characterized by elemental analyses, IR, ¹H, and ¹³C NMR techniques. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:503–506, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20153     

Original recyclization of S‐phenacyl derivatives of 4‐acylamino‐2‐mercapto‐1,3‐oxazoles and their analogues

Readily accessible acylamino(chloro)acetophenones, if treated with sodium rhodanide and α‐halogenocarbonyl compounds, provide 4‐acylamino‐5‐aryl‐2‐mercapto‐1,3‐oxazole derivatives which undergo recyclization on heating in polyphosphoric acid to give substituted 1,3‐thiazol‐2(3H)‐ones or 1,3‐thiazolidin‐2,4‐diones containing 2‐alkyl(aryl)‐5‐aryl‐1,3‐oxazol‐4‐yl residues at the N³ atom. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:432–437, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20317     

Suzuki–Miyaura coupling reactions of aryl chlorides catalyzed by a new nickel(II) σ‐aryl complex

A new nickel(II) σ‐aryl complex, trans‐chloro(9‐phenanthrenyl)bis(triphenylphosphine)nickel(II), was used as a precatalyst for the Suzuki–Miyaura coupling reactions of aryl chlorides. The catalytic conditions were optimized by investigating the cross‐coupling of p‐chloroanisole with phenylboronic acid. The results show that this complex is efficient for both electron‐rich and electron‐deficient aryl chlorides, though it gives better yields for activated arylboronic acids than deactivated ones. All isolated cross‐coupled biaryl products have been characterized by ¹H and ¹³C NMR, and their spectral data are consistent with those reported. Side products from the coupling of arylboronic acid with the precatalyst complex have also been isolated and characterized, which is helpful for understanding the coupling mechanism. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthesis of 5‐methyl‐4‐oxo‐2‐(coumarin‐3‐yl)‐N‐aryl‐3,4‐dihydrothieno[2,3‐d]‐pyrimidine‐6‐carboxamides

Possible approaches to synthesis of 5‐methyl‐4‐oxo‐2‐(coumarin‐3‐yl)‐N‐aryl‐3,4‐dihydrothieno[2,3‐d]pyrimidine‐6‐carboxamides 4 have been discussed. It is shown that the preferable approach is cyclization of 2‐iminocoumarin‐3‐carboxamides 1 , utilizing 5‐amino‐3‐methyl‐N²‐arylthiophene‐2,4‐dicarboxamides 2 as binucleophilic reagents. The proposed procedure allowed us to easily obtain 4 in two stages, using common reagents. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:341–346, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20303     

New cyclization of N‐hydroxyiminoyl chlorides with N‐alkyl ethynesulfonamides: Synthesis of 4‐alkyl‐3‐aryl‐4,5‐dihydro‐1,5,2,4‐oxathiadiazepine‐5,5‐diones

N‐Hydroxyiminoyl chlorides reacted with N‐alkyl ethynesulfonamides in the presence of triethylamine in CH₂Cl₂ to afford the 4‐alkyl‐3‐aryl‐4,5‐dihydro‐1,5,2,4‐oxathiadiazepine‐5,5‐diones (3) as the major products together with N‐alkyl‐3‐aryl‐5‐isoxazolesulfonamides (4). © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 461–464, 1999     

Pentafluoro(aryl)‐λ6‐tellanes and Tetrafluoro(aryl)(trifluoromethyl)‐λ6‐tellanes: From SF5 to the TeF5 and TeF4CF3 Groups

The TeF₅ group is significantly underexplored as a highly fluorinated substituent on an organic framework, despite it being a larger congener of the acclaimed SF₅ group. In fact, only one aryl‐TeF₅ compound (phenyl‐TeF₅) has been reported to date, synthesized using XeF₂. Our recently developed mild TCICA/KF approach to oxidative fluorination provides an affordable and scalable alternative to XeF₂. Using this method, we report a scope of extensively characterized aryl‐TeF₅ compounds, along with the first SC‐XRD data on this compound class. The methodology was also extended to the synthesis and structural study of heretofore unknown aryl‐TeF₄CF₃ compounds. Additionally, preliminary reactivity studies unveiled some inconsistencies with previous literature regarding phenyl‐TeF₅. Although our studies conclude that the arene‐based TeF₅ (and TeF₄CF₃) group is not quite as robust as the SF₅ group, we find that the TeF₅ group is more stable than previously thought, thus opening a door to explore new applications of this motif.     

Dppc+PF6−–PdCl2–[bmim][PF6]–a copper‐free recyclable catalytic system for Sonogashira coupling reaction

An air‐stable, copper‐free and highly efficient Dppc⁺PF₆^?–PdCl₂–[bmim][PF₆] catalytic system has been developed for the Sonogashira coupling reaction of aryl iodides with various aryl‐ and alkylacetylenes. The catalytic system allows for facile separation and can be recycled at least eight times with minimal loss of activity. Copyright © 2007 John Wiley & Sons, Ltd.     

BiCl3‐catalyzed carbon‒carbon cross‐coupling of organoboronic acids with aryl iodides

A procedure for BiCl₃‐catalyzed carbon‐carbon cross‐coupling reaction of organoboronic acids with aryl iodides is described. This protocol has a wide substrate scope and uses an inexpensive and non‐toxic catalyst. Copyright © 2013 John Wiley & Sons, Ltd.     

Suzuki reaction of aryl chlorides using saturated N‐heterocarbene ligands

From readily available starting materials, six 1,3‐dialkyl‐imidazolinium bromides ( 2a–f ) have been prepared and characterized by conventional spectroscopic methods and elemental analyses. The incorporation of saturated N‐heterocyclic carbenes into palladium precatalysts gives high catalyst activity in the Suzuki coupling of deactivated aryl chloride substrates in aqueous media. The complexes were generated in the presence of Pd(OAc)₂ by in situ deprotonation of 2a–f . © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:557–561, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20140     

Iron‐catalyzed cross‐coupling of heteroaromatic tosylates with alkyl and aryl Grignard reagents

An Fe(III)‐catalyzed cross‐coupling of N‐heteroaromatic tosylates with aryl and alkyl Grignard reagents is presented. The reaction proceeds at ?20°C to room temperature with short reaction time (15–30 min.), and the corresponding products are obtained with moderate to high yields. In particular, low‐cost and abundantly available FeCl₃ or Fe(acetylacetonate)₃ catalyze the reaction without other special ligands. All tested N‐heteroaromatic tosylates that are available including pyridine and pyrimidine derivatives were subject to the reaction, resulting in the expected products. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis and properties of fluorine‐containing poly(aryl ether oxadiazole)s

Fluorine‐containing poly(aryl ether 1,3,4‐ozadiazole)s were synthesized by the nucleophilic aromatic substitution reaction of 2,5‐bis(2,3,4,5,6‐pentafluorophenyl)‐1,3,4‐oxadiazole and various bisphenols in the presence of potassium carbonate. The polymerizations were carried out at 30 °C in 1‐methyl‐2‐pyrrolidinone to avoid the gelation caused by a crosslinking reaction at para and ortho carbons to the 1,3,4‐oxidiazole ring. The obtained polymers were all para‐connected linear structures. The obtained fluorine‐containing poly(aryl ether 1,3,4‐ozadiazole)s showed excellent solubility and afforded tough, transparent films by the solution‐casting method. They also exhibited a high glass transition temperature depending on the molecular structure, and the glass transition temperature could be controlled by the bisphenols in the range of 157–257 °C. They showed good thermal stability and excellent hydrophobicity due to the incorporation of the 2,3,5,6‐tetrafluoro‐1,4‐phenylene moiety. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2855–2866, 2007