Preparation of N-Arylsulfonyl Imines from Sulfonamides and Aryl Aldehydes Using Magnesium Oxide as a Heterogeneous and Reusable Catalyst Under Solvent-Free Conditions

An efficient solvent-free procedure for the preparation of N-arylsulfonyl imines from sulfonamides and aryl aldehydes in the presence of a catalytic amount of magnesium oxide and tetrabutylammonium bromide (TBAB) under microwave irradiation is described. The advantages of this method are good to high yields, short reaction times, low cost, and matching with green chemistry protocols.     

Copper-catalyzed N-arylation of sulfonamides with aryl bromides and iodides using microwave heating

The copper-catalyzed N-arylation of sulfonamides with a variety of aryl bromides and iodides using microwave heating is described.     

Palladium-catalyzed intermolecular coupling of aryl chlorides and sulfonamides under microwave irradiation

[reaction: see text] An efficient intermolecular N-arylation of sulfonamides with aryl chlorides is realized using palladium catalysis. The reaction proceeds under microwave irradiation at 180-200 degrees C for 10 min with 2-10 mol % of Pd catalyst in 32-85% isolated yields.     

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.     

A general and mild two-step procedure for the synthesis of aryl and heteroaryl sulfonamides from the corresponding iodides

A mild two-step preparation of aryl and heteroaryl sulfonyl chlorides and sulfonamides from their corresponding iodides is developed. Acid labile functionalities are shown to be stable under both the copper-catalysed coupling and the subsequent oxidative chlorination.     

Microwave-promoted aminocarbonylation of aryl triflates using Mo(CO)6 as a solid CO source

Palladium-catalyzed carbonylations of aryl triflates with a range of nucleophiles using Mo(CO)₆ as a solid CO source were explored. The reactions proceeded smoothly providing moderate to good yields of the corresponding aryl amides, esters, or acylsulfonamides after only 20 min of microwave irradiation. The acyl transfer reagent 4-dimethylaminopyridine was found to promote some of the more difficult transformations.     

Microwave-assisted synthesis utilizing supported reagents: a rapid and versatile synthesis of 1,5-diarylpyrazoles

The application of microwave heating to a silica-assisted solution-phase synthesis technique has been utilized to develop a rapid and efficient two-step protocol for the preparation of pyrazoles from aryl methyl ketone and aryl hydrazine monomers.     

5-(hydroxymethyl)oxazoles: versatile scaffolds for combinatorial solid-phase synthesis of 5-substituted oxazoles

A scheme combining the preparation of building blocks in solution followed by solid-phase combinatorial chemistry has been developed to side-chain diversify 5-(hydroxymethyl)oxazole scaffold (1) into aryl ethers, thioethers, sulfones, sulfonamides, and carboxamides. Protected heterocyclic scaffolds 2 were linked to the solid phase and N-terminal derivatized using active ester chemistry, providing chemset 4?1-4,1-4?. The free side-chain hydroxyl of 4 was smoothly converted to aryl ethers 6 under Mitsunobu conditions, with a broad range of substituted phenols. Alternatively, quantitative conversion of hydroxyl to bromide followed by displacement with alkyl and aryl thiols gave thioethers 8. Thioethers were optionally oxidized to sulfones 9. Bromide displacement by azide, followed by reduction to amine and acylation with a range of carboxylic acids and sulfonyl chlorides gave carboxamides 11 and sulfonamides 13, respectively. Crude purity at typically >90% was observed for each of the five modifications detailed. A series of 20 compounds, exemplifying each modification, was reprepared, purified, and fully characterized.     

A robust method for the Hiyama-type coupling of arylsiloxanes and disiloxanes with aryl halides

Palladium catalysed Hiyama-type coupling of aryl disiloxanes or aryl silanols with aryl halides in the presence of stoichiometric silver(I) oxide and catalytic TBAF allows the rapid preparation of biaryls in moderate to high yield under mild thermal or microwave irradiation conditions.     

Facile synthesis of acyl sulfonamides from carboxyic acids using the Mukaiyama reagent

A fast and convenient method using the Mukaiyama reagent was developed to prepare acyl sulfonamides from carboxylic acids and sulfonamides. This methodology is effective for a range of acids and sulfonamides proceeding in moderate to good yields with the majority of reactions complete within one hour under the optimized condition.     

Boron trichloride as an efficient and selective agent for deprotection of tert-butyl aryl sulfonamides

A fast, mild and selective method for deprotection of tert-butyl aryl sulfonamides utilizing BCl₃ as deprotection reagent has been developed. A variety of tert-butyl aryl sulfonamides used under these conditions gave the corresponding primary sulfonamides in high yields. The method does not cleave methoxy groups and prevents incorporation of tert-butyl groups onto electron-rich aromatic rings.     

Microwave-assisted copper-catalyzed preparation of diaryl chalcogenides

Diaryl chalcogenide synthesis employing diaryl dichalcogenides and aryl halides as starting materials in the presence of excess magnesium and a catalytic amount of CuI/bipyridyl is significantly improved by microwave heating. Reaction times can be reduced from 2 to 3 days to 6-8 h. Both aryl bromides and aryl chlorides can be used as substrates in the substitution reaction. The procedure is useful not only for diaryl sulfide and diaryl selenide synthesis but also for the preparation of unsymmetrical diaryl tellurides. Starting from suitable aryl halides, the novel microwave-assisted procedure was used for the facile preparation of novel chalcogen analogues (PhS-, PhSe-, and PhTe-) of various antioxidants (ethoxyquin and 3-pyridinol). Attempts to use dialkyl dichalcogenides for the coupling of alkylchalcogeno moieties to aryl halides were only successful in the case of long-chain (such as n-octyl) disulfides and diselenides.     

Cu(II)-catalyzed decarboxylation/elimination of N-arylsulfonyl amino acids to primary aryl sulfonamides

A novel protocol for CuO-catalyzed decarboxylation/elimination of N-arylsulfonyl amino acids was developed. It is the first example of using an accessible amino acid as an ammonia synthetic equivalent for the synthesis of primary aryl sulfonamides via oxidative decarboxylation/elimination reactions. The present protocol shows excellent functional group tolerance and provides an efficient method for the synthesis of primary aryl sulfonamides in excellent yields.     

N-(吡啶-2-基羰基)取代芳基磺酰胺的合成及除草活性

N-(吡啶-2-基羰基)取代芳基磺酰胺的合成及除草活性     

A new strategy for the synthesis of benzylic sulfonamides: palladium-catalyzed arylation and sulfonamide metathesis

An efficient two-step strategy has been developed to access diversely functionalized benzylic sulfonamides. Execution of this strategy required the development of two reaction methods: the palladium-catalyzed cross-coupling of aryl halides with CH-acidic methanesulfonamides and a metathesis reaction between the resulting alpha-arylated sulfonamides and diverse amines. The broad scope of the cross-coupling process combined with a versatile sulfonamide metathesis constitutes an efficient strategy for the synthesis of various benzylic sulfonamides.     

A useful Pd-catalyzed Negishi coupling approach to benzylic sulfonamide derivatives

A mild catalytic system to access diversely functionalized benzylic sulfonamides has been developed. Palladium-catalyzed alpha-arylation by Negishi cross-coupling of sulfonamide-stabilized anions and a wide range of aryl iodides, bromides, and triflates constitutes a practical strategy for the synthesis of various benzylic sulfonamides.     

Harnessing the catalytic behaviour of 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP): An expeditious synthesis of thioesters

A novel, efficient, metal-, base- and acid-free straightforward protocol has been developed for the construction of useful thioesters. The immense catalytic potential of HFIP for promoting the thiocarbonylation of acyl halides and thiols is disclosed. HFIP was recovered with ease and reused for further reactions without any loss of reactivity. Both aryl and alkyl thiols bearing electron-donating and electron-withdrawing groups as well as aryl- and alkyl acyl halides worked well in this reaction. Inexpensive precursors, short reaction time, obviating workup, high atom economy, and gram-scale preparation are the significant features of the developed eco-friendly route for S-carbonylation of thiols.     

Palladium‐Catalyzed Site‐Selective C−H Functionalization of Weakly Coordinating Sulfonamides: Synthesis of Biaryl Sulfonamides

A novel and site selective C?H functionalization of unsubstituted sulfonamides has been developed for the synthesis of ortho aryl sulfonamides. The reaction involves highly regioselective ortho mono arylation of weakly coordinating SO₂NH₂ directing group by means of aryl iodides. Palladium acetate in the presence of silver(I) oxide is found to be the most effective catalytic system.     

Recognition properties of carboxylic acid bioisosteres: anion binding by tetrazoles, aryl sulfonamides, and acyl sulfonamides on a calix[4]arene scaffold

Tetrazoles and acyl sulfonamides are functional groups that are common in medicinal chemistry but virtually unexplored as recognition elements in supramolecular chemistry. We report here on the anion binding properties of these highly acidic N-H functional groups. We have prepared two new calixarene-based tetrazole-containing hosts, as well as new acetyl sulfonamide and benzoyl sulfonamide hosts. We also report on analogous hosts bearing the better-known aryl sulfonamide functional group as a point of comparison. We find that these hosts are competent anion binders and that the recognition of anions by these groups is highly dependent on their conformational preferences. We also report in detail on the preferred molecular shape of each acid bioisostere as determined by calculations and structural database surveys, and discuss how these shapes impact binding in the context of the reported hosts.     

Biaryl and Aryl Ketone Synthesis via Pd‐Catalyzed Decarboxylative Coupling of Carboxylate Salts with Aryl Triflates

A bimetallic catalyst system has been developed that for the first time allows the decarboxylative cross‐coupling of aryl and acyl carboxylates with aryl triflates. In contrast to aryl halides, these electrophiles give rise to non‐coordinating anions as byproducts, which do not interfere with the decarboxylation step that leads to the generation of the carbon nucleophilic cross‐coupling partner. As a result, the scope of carboxylate substrates usable in this transformation was extended from ortho‐substituted or otherwise activated derivatives to a broad range of ortho‐, meta‐, and para‐substituted aromatic carboxylates. Two alternative protocols have been optimized, one involving heating the substrates in the presence of Cu^I/1,10‐phenanthroline (10–15 mol %) and PdI₂/phosphine (2–3 mol %) in NMP for 1–24 h, the other involving Cu^I/1,10‐phenanthroline (6–15 mol %) and PdBr₂/Tol‐BINAP (2 mol %) in NMP using microwave heating for 5–10 min. While most products are accessible using standard heating, the use of microwave irradiation was found to be beneficial especially for the conversion of non‐activated carboxylates with functionalized aryl triflates. The synthetic utility of the transformation is demonstrated with 48 examples showing the scope and limitations of both protocols. In mechanistic studies, the special role of microwave irradiation is elucidated, and further perspectives of decarboxylative cross‐couplings are discussed.