Sulfonylation of arenes with sulfonamides

In the presence of triflic anhydride, sulfonylation of arenes with sulfonamides proceeded smoothly in Cl₂CHCHCl₂ at 80-140 °C, which gave rise to the desired products in good to excellent yields.     

Efficient microwave-assisted synthesis of 4-amino-2-benzazepin-3-ones as conformationally restricted dipeptide mimetics

In this paper, we describe the synthesis of conformationally constrained dipeptide mimetic derivatives. Microwave flash heating was used in several synthetic steps providing the opportunity to perform the reactions in dramatically shortened time as well as to increase the obtained yields. The efficiency of the methodology makes it useful in order to prepare other dipeptides containing the 4-amino-tetrahydro-2-benzazepin-3-one motif.     

Synthesis and characterization of benzo[c]thiophene analogs tethered with dibenzo-heterocycles as potential OLEDs

Synthesis of mixed heterocyclic system containing benzo[c]thiophene, dibenzo-heterocycles, and thiophene unit is described.     

Indirect regioselective heteroarylation of indoles through a Friedel-Crafts reaction with (E)-1,4-diaryl-2-buten-1,4-diones

A two-step synthesis of 3-heteroaryl indoles has been developed. The first step of the sequence involves a Friedel-Crafts alkylation of indoles with 1,4-diaryl-2-buten-1,4-diones to give the corresponding indoles bearing a 1,4-dicarbonyl moiety. The reaction is catalyzed by InCl₃ and takes place with good yields. Cyclization of the diones under different Paal-Knorr conditions allows to prepare indoles substituted at the C3 position with 3-furanyl, 3-pyrrolyl- and 3-thienyl moieties.     

Synthesis of 3-geranyl- and 3-prenyl-2,4,6-trihydroxybenzophenone

Biologically active phenyl[3-(3,7-dimethyl-2,6-octadienyl)-2,4,6-trihydroxyphenyl]methanone (2) and phenyl[2,4,6-trihydroxy-3-(3-methyl-2-butenyl)phenyl]methanone (3) were synthesized by an efficient and convenient synthetic sequence. The reaction steps of this synthesis included methylation, Friedel-Crafts acylation, demethylation and geranylation steps.     

Reaction of 2-propargylphenylcarbamates with diphenyliodonium salts via Meyer-Schuster rearrangement

The syntheses of 2,3-dihydro-4-quinolones from 2-propargylphenylcarbamates by one-pot tandem process that involves Meyer-Schuster rearrangement or arylative Meyer-Schuster rearrangement/Michael addition of carbamate nitrogen to the resulting vinyl ketones have been developed. Phenylcarbamates tethering tertiary propargyl alcohols underwent arylative Meyer-Schuster rearrangement/Friedel-Crafts alkylation to produce 2,3-dihydroindenones.     

Asymmetric Friedel-Crafts alkylation of activated benzenes with methyl (E)-2-oxo-4-aryl-3-butenoates catalyzed by [Pybox/Sc(OTf)3]

The asymmetric Friedel-Crafts reaction between methyl (E)-2-oxo-4-aryl-3-butenoates (1a-c) and activated benzenes (2a-d) has been efficiently catalyzed by the Sc^III triflate complex of (4′S,5′S)-2,6-bis[4′-(triisopropylsilyl) oxymethyl-5′-phenyl-1′,3′-oxazolin-2′-yl]pyridine (pybox 3). The 4,4-diaryl-2-oxo-butyric acid methyl esters (4) are usually formed in good yields and the enantioselectivity is up to 99% ee. The sense of the stereoinduction can be rationalized with the same octahedral complex (10) between 1, pybox 3 and Sc triflate already proposed for other reactions involving pyruvates, and catalyzed by the same complex.     

Ab initio study of the mechanism of the formation of p-rosolic acid from trifluoromethoxybenzene under HF/Lewis acid conditions

The mechanism of the formation of p-rosolic acid from trifluoromethoxybenzene under HF/Lewis acid conditions was studied using ab initio methods. A series of cationic intermediates is initiated by the expulsion of a fluorine atom of trifluoromethoxybenzene with anomeric assistance of the trifluoromethoxy oxygen. The resulting difluorocarbonium ion is attacked by a second trifluoromethoxybenzene to generate the first carbon-carbon bond on what will be the central carbon of p-rosolic acid. Elimination of phenol results in the formation of cationic intermediate 4 which is susceptible to carbon-alkylation by the same phenol to form the second carbon-carbon bond. Attack on subsequent difluorocarbonium ions by trifluoromethoxybenzene strips trifluoromethyl groups from the downstream intermediates, eventually leading to p-rosolic acid, and continues the generation of 4, each of which initiate a fresh mechanistic series toward another p-rosolic acid molecule.     

High-Throughput Synthesis of Alkylbenzophenones with Indium Triflate in the Absence of Solvents Using Microwave

Abstract

A series of alkylbenzophenones were rapidly and efficiently prepared from alkylbenzenes and benzoyl chlorides by Friedel-Crafts acylation catalyzed with indium triflate under solvent-free conditions by microwave heating.     

Comparisons of O-acylation and Friedel-Crafts acylation of phenols and acyl chlorides and Fries rearrangement of phenyl esters in trifluoromethanesulfonic acid: effective synthesis of optically active homotyrosines

Reactions involving phenol derivatives and acyl chlorides have to be controlled for competitive O-acylations and C-acylations (Friedel-Crafts acylations and Fries rearrangements) in acidic condition. The extent for these reactions in trifluoromethanesulfonic acid (TfOH), which is used as catalyst and solvent, is examined. Although diluted TfOH was needed for effective O-acylation, concentrated TfOH was required for effective C-acylations in mild condition. These results have been applied to the novel synthesis of homotyrosine derivatives. Both Fries rearrangement of N-TFA-Asp(OBn)-OMe and Friedel-Crafts acylation of phenol with N-TFA-Asp(Cl)-OMe in TfOH afforded the homotyrosine skeleton, followed by reduction and deprotection afforded homotyrosines maintaining stereochemistry of Asp as an optically pure form.