Copper-mediated fluorination of aryl iodides

The synthesis of aryl fluorides has been studied intensively because of the importance of aryl fluorides in pharmaceuticals, agrochemicals, and materials. The stability, reactivity, and biological properties of aryl fluorides can be distinct from those of the corresponding arenes. Methods for the synthesis of aryl fluorides, however, are limited. We report the conversion of a diverse set of aryl iodides to the corresponding aryl fluorides. This reaction occurs with a cationic copper reagent and silver fluoride. Preliminary results suggest this reaction is enabled by a facile reductive elimination from a cationic arylcopper(III) fluoride.     

Copper catalyzed aryl amidation between Nα-Fmoc-protected amino-acid azides and aryl boronic acids

Abstract

A simple and efficient method for the synthesis of aryl amides via oxidative copper-catalyzed coupling of commercially available aryl boronic acids and bench stable N^α-protected amino-acid azides is reported. The potential utility of this protocol is demonstrated through a survey of diversely substituted aryl boronic acids and several side-chain functionalized amino-acid azides, leading to the preparation of the desired amidated products in good to excellent yields. This amide synthesis is suitable for the preparation of amides (such as peptide aryl amides and sterically hindered amino acids) that are not or hardly accessible via classical approaches.     

Microwave-assisted selenium dioxide oxidation of aryl methyl ketones to aryl glyoxals

We report an improved procedure for the synthesis of phenyl glyoxal and a series of para-substituted aryl glyoxals by microwave-assisted selenium dioxide oxidation. The reaction time has been reduced from several hours to three minutes for activated aryl methyl ketone substrates and 18 min for deactivated substrates, with all reactions affording quantitative conversion into the corresponding aryl glyoxals.     

Metal-free synthesis of aryl esters by coupling aryl carboxylic acids and aryl boronic acids

A facile synthesis of aryl esters is developed by coupling aryl carboxylic acids and aryl boronic acids in the presence of PhI(OAc)₂ and carbonyl diimidazole. A wide range of functional groups were tolerant to the metal-free reaction condition that led to the desired products in good yields.     

Copper-catalyzed aerobic oxidation and cleavage/formation of C-S bond: a novel synthesis of aryl methyl sulfones from aryl halides and DMSO

With atmospheric oxygen as the oxidant, a novel copper(I)-catalyzed synthesis of aryl methyl sulfones from aryl halides and widely available DMSO is described. The procedure tolerates aryl halides with various functional groups (such as methoxy, acetyl, chloro, fluoro and nitro groups), which could afford aryl methyl sulfones in moderate to high yields. The copper-catalyzed aerobic oxidation and the cleavage/formation of C-S bond are the key steps for this transformation.     

Fmoc-SPPS chemistry compatible approach for the generation of (glyco)peptide aryl thioesters

A new approach is described for the general Fmoc-based solid-phase synthesis of (glyco)peptide aryl thioesters. A peptide alkyl oxoester obtained by standard Fmoc-based chain elongation undergoes an O-to-S acyl shift, and is followed by alkyl thioester exchanges with a large excess of aryl thiol, affording the corresponding peptide aryl thioester. The newly developed methodology is useful for the chemical synthesis of post-translationally modified proteins because of its compatibility with standard Fmoc-SPPS conditions. In addition, the peptide aryl thioesters are essential intermediates for chemical synthesis of proteins by kinetically controlled convergent strategy.     

Synthesis of dendritic oligo(aryl sulfone)s as supports for synthesis

A short, divergent route to G₁ oligo(aryl sulfone)s and a G₂ oligo(aryl sulfone) dendrimer using nucleophilic aromatic substitution reactions is described. A range of tetrasubstituted pentasulfones are proposed for applications as homogeneous supports for synthesis. Key to achieving selectivity in the syntheses is the activation of leaving groups by sulfide to sulfone oxidation. Preparation of the G₂ oligo(aryl sulfone) is low-yielding due to competition from SET processes that are interesting from a mechanistic point of view. The utility of the supports is exemplified with a four step synthesis of a dipeptide and by ‘react and release’ synthesis of amides.     

An efficient synthesis of enantiomerically pure unnatural aryl glycinols and aryl glycines

A quick route to enantiomerically pure unnatural aryl glycinols and aryl glycines has been established based on an asymmetric azidation reaction using a chiral benzosultam auxiliary. The synthesis of aryl glycinols involves three steps starting from arylacetic acids, and the chiral auxiliary can be readily recovered.     

Palladium-catalyzed cross-coupling reactions of aryl mesylates

Palladium-catalyzed cross-coupling reactions are state-of-the art methods for synthesis of many important compounds. The development of the use of the phenol-derived sulfonated hydroxyl group in the coupling reactions is highly attractive as the hydroxyl group is commonly present in organic compounds and they are versatile alternatives to aryl halides in cross-coupling reactions. In this tutorial review, we summarize the current development of palladium-catalyzed cross-coupling reactions of aryl mesylates.     

Palladium-catalysed symmetrical and unsymmetrical coupling of aryl halides

Pd(OAc)₂ is a convenient catalyst under basic conditions for the synthesis of symmetrical biaryl moieties from aryl halides. This homocoupling of aryl halides is a good catalytic alternative to classical biaryl formations involving stoichiometric amounts of metal. This method is compatible with sensitive functional groups. We also studied the extension of this reaction to unsymmetrical aryl coupling.     

Iodine-mediated aryl transfer reaction from arylhydrazine hydrochlorides to nitriles

An iodine-promoted, metal-, base-, and solvent-free cross-coupling reaction was developed for the synthesis of various useful secondary amides via an aryl N-addition reaction of aryl groups to cyano groups. This aryl transfer reaction proceeds with arylhydrazine hydrochlorides serving as the aryl donors. A labelling experiment shows that the N atom in the product comes from the cyano group of the nitriles, which are low in cost. A plausible radical-driven mechanism is also proposed.     

Ni(COD)2/PCy3 catalyzed cross-coupling of aryl and heteroaryl neopentylglycolboronates with aryl and heteroaryl mesylates and sulfamates in THF at room temperature

Reaction conditions for the Ni(COD)(2)/PCy(3) catalyzed cross-coupling of aryl neopentylglycolboronates with aryl mesylates were developed. By using optimized reaction conditions, Ni(COD)(2)/PCy(3) was shown to be a versatile catalyst for the cross-coupling of a diversity of aryl neopentylglycolboronates with aryl and heteroaryl mesylates and sulfamates containing both electron-donating and electron-withdrawing substituents in their para, ortho, and meta positions in THF at room temperature. This Ni-catalyzed cross-coupling of aryl neopentylglycolboronates is also effective for the synthesis of heterobiaryls and biaryls containing electrophilic functionalities sensitive to organolithium and organomagnesium derivatives. In combination with the recently developed Ni-catalyzed neopentylglycolborylation, all Ni-catalyzed routes to functional biaryls and heterobiaryls are now easily accessible.     

Copper-mediated cross-coupling of aryl boronic acids and alkyl thiols

[reaction: see text] The cross-coupling of aryl boronic acids and alkanethiols mediated by copper(II) acetate and pyridine in anhydrous dimethylformamide affords aryl alkyl sulfides in good yield with a wide variety of substituted aryl boronic acids. The method is applicable to the synthesis of aryl sulfides of cysteine.     

Solid-phase synthesis of alkyl aryl ethers via the Ullmann condensation

Alkyl aryl ether formation is a frequently employed reaction in organic synthesis. Ullmann condensation is an alternative method to the widely used Mitsunobu reaction and is very useful in situations where application of the Mitsunobu reaction is limited. By application of this reaction to solid-phase synthesis of a series of alkyl aryl ethers, reaction conditions (catalyst, solvent, temperature, time, etc.) for a sterically hindered class of alcohols were investigated and optimized. A range of aryl halides was used to explore the scope of the reaction in solid phase.     

Synthesis of aryl benzyl NH-sulfoximines

Efficient synthesis and characterisation of a series of aryl benzyl NH-sulfoximines are described. While N-protected versions of aryl benzyl sulfoximines have been previously described, reports of their deprotection are very limited, presumably due to lability under the typically harsh deprotection conditions which can be employed with the less reactive aryl alkyl derivatives. Use of N-cyanosulfoximines as key intermediates overcomes these difficulties leading to an effective synthetic route to these compounds.     

Copper oxide nanoparticles catalyzed synthesis of aryl sulfides via cascade reaction of aryl halides with thiourea

Recyclable copper oxide nanoparticles catalyzed simple and highly efficient protocol for the synthesis of symmetrical aryl sulfides was developed by the cross-coupling of aromatic halides with inexpensive and commercially available thiourea which was used as an effective sulfur surrogate. The present cross-coupling protocol of thiourea, via cascade reaction with various substituted aryl halides, producing desired aryl sulfides, has an added advantage of avoiding foul-smelling thiols.     

"One-pot" two-step synthesis of aryl sulfur compounds by photoinduced reactions of thiourea anion with aryl halides

[reaction: see text]. The photoinduced reactions of aryl halides with the thiourea anion afford arene thiolate ions in DMSO. These species without isolation, and by a subsequent aliphatic nucleophilic substitution, S(RN)1 reaction, oxidation, or protonation, yield aryl methyl sulfides, diaryl sulfides, diaryl disulfides, and aryl thiols with good yields (50-80%). This is a simple and convenient approach which involves the use of the commercially available and inexpensive thiourea in a "one-pot" two-step process for the synthesis of aromatic sulfur compounds.     

Science and technology of perfluorocyclobutyl aryl ether polymers

This article highlights the preparation of perfluorocyclobutyl (PFCB) aryl ether polymers for a multitude of commercial technologies that are of academic and commercial global interest. In this account, the synthesis of various aryl trifluorovinyl ether (TFVE) monomers tailored for specific applications is discussed. The preparation of PFCB aryl ether polymers and their properties is then presented. Topics of PFCB aryl ether polymers and their applications include photonics, polymer light emitting diodes (PLEDs), proton exchange membranes (PEMs) for fuel cells, atomic oxygen (AO) resistant coatings, and hybrid composites. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5705–5721, 2007     

Synthesis of aryl α-keto esters via the rearrangement of aryl cyanohydrin carbonate esters

A facile synthesis of aryl α-keto esters is reported involving the rearrangement of aryl cyanohydrin carbonate esters induced by the α-carbanion to the nitrile group generated by LDA. However, under similar conditions, an o-benzyloxycyanohydrin carbonate ester rearranged via a domino reaction leading to 2-phenylbenzofuran-3-carboxylic acid.     

Application of the Pictet-Spengler reaction to aryl amine substrates linked to deactivated aromatic heterosystems

Three new substrates with an aryl amine moiety attached to quinoxalines, triazoles and tetrazoles either via C or N have been used for the Pictet-Spengler reaction. The substrates have been designed by applying the concept of ‘aryl amine attached to a deactivated heteroaromatic ring’ in a manner to facilitate endo cyclization. This is in contrast to the substrates used traditionally and reported earlier by us that are based on either aliphatic or aryl amine, respectively, attached to an activated heterocyclic ring. The Pictet-Spengler condensation of the three substrates with aldehydes led to the synthesis of novel N-rich polyheterocyclic system hitherto not reported. Our modified strategy opens up possibilities to design novel substrates with aryl amines linked via C or N to either deactivated or activated heterocyclic privileged structure, which in turn can be used for the synthesis of novel fused polyheterocyclic skeletons.