Convenient method for the synthesis of C-phosphorylated N-arylformamidines

C-Phosphorylated (P^V) arylformamidines have been prepared by the reaction of N-arylamidotrichloromethyl derivatives of phosphorus, thiophosphorus, and selenophosphorus acids with secondary amines. Dependence of the reaction on the nature of chalcogene, electronic and steric factors has been studied. By reduction of N-arylformamidinophosphonoselenides the corresponding C-phosphorylated (P^III) arylformamidines have been synthesized.     

One-pot synthesis of 12H-benzo[b]xanthen-12-ones and naphtha[2,3-b]furans from non-naphthalene substrates

An efficient one-pot synthesis of 12H-benzo[b]xanthen-12-ones via an oxidant initiated and base promoted tandem reaction of 2-(4-(2-haloaryl)-4-hydroxybut-1-ynyl)benzaldehydes has been developed. By using similar strategy, a one-pot synthesis of naphtha[2,3-b]furans from the cascade reaction of 2-(4-hydroxy-but-1-ynyl)benzaldehydes with 2-bromoacetonitrile or α-bromocarbonyl compounds has also been achieved.     

Synthesis of methyl (5Z,8Z,10E,12E,14Z)-eicosapentaenoate

The first total synthesis of methyl (5Z,8Z,10E,12E,14Z)-eicosapentaenoate has been achieved in seven steps and in 16% overall yield. The synthesis confirmed the assigned structure of this polyunsaturated natural product.     

Determination of microcystin-LR in surface water using high-performance liquid chromatography/tandem electrospray ionization mass detector

The need for a rapid, sensitive, and reliable analytical method for microcystin-LR has been emphasized by the awareness of toxic cyanobacteria as a human-health risk through drinking water. Microcystin-LR is the most commonly reported microcystin which is produced by cyanobacteria. The WHO guideline for microcystin-LR in drinking water is 1 μg/l. In this paper, an effective method has been developed by application of high-performance liquid chromatography/tandem electrospray ionization mass detector in the determination of microcystin-LR in surface water sample. At the LC-MS-MS CID-full scan mode, different relative collision energies have been tested with 30% being used for further microcystin-LR analysis. The possible mass dissociation path has been proposed. Based on 30% relative collision energy, present method has an excellent method detection limit (MDL), which is as low as 2.6 ng/l. To the best of our knowledge, this represents one of the most sensitive methods in existence for the microcystin-LR analysis. This method has also been validated by evaluation of the calibration linearity, precision, accuracy, recovery, and mass ratio stability.     

N-tert-Butyl-N-chlorocyanamide: a new reagent for the efficient preparation of gem-chloronitroso compounds

A new reagent for the efficient preparation of gem-chloronitroso compounds has been developed. The reaction of ketoximes with N-tert-butyl-N-chlorocyanamide takes place instantaneously in carbon tetrachloride at room temperature with excellent yields under mild conditions.     

One pot conversion of azido arenes to N-arylacetamides and N-arylformamides: synthesis of 1,4-benzodiazepine-2,5-diones and fused [2,1-b]quinazolinones

Sodium iodide in acidic media has been employed for the synthesis of N-arylformamides and N-arylacetamides. The NaI/acetic acid reagent system has also been extended for the synthesis of 1,4-benzodiazepine-2,5-diones, pyrrolo[2,1-c][1,4]benzodiazepine-5,11-diones, and fused [2,1-b]quinazolinones.     

Diastereoselective synthesis of homo-N,O-nucleosides

A new class of homo-N,O-nucleosides has been designed, based on the 1,3-dipolar cycloaddition of C-substituted nitrones with allyl nucleobases. The N-methyl-C-ethoxycarbonyl nitrone 1, and the C-α-silyloxymethyl-N-methyl nitrone 7 have been exploited: the stereochemical features of the obtained nucleosides are dependent on the nature of the dipole. The results obtained with DFT calculations fully agree with the experimental results and successfully reproduce the experimentally observed reversal of endo/exo selectivity for nitrones 1 and 7.     

PTSA catalyzed straightforward protocol for the synthesis of 2-(N-acyl)aminobenzimidazoles and 2-(N-acyl)aminobenzothiazoles in PEG

An efficient PTSA catalyzed synthesis of 2-(N-acyl)aminobenzimidazoles and 2-(N-acyl)aminobenzothiazoles has been described using S-ethylated-N-acylthioureas as substrates and polyethylene glycol as solvent.     

Highly selective acetoxylation of sulfonamides via using phenyliodine(III) diacetate

A highly efficient acetoxylation reaction of N-aryl-arylsulfonamides has been developed, presumably proceeding via the selective functionalization of N-aryl C–H bonds. A stoichiometric amount of PhI(OAc)₂ was generally employed as the oxidation reagent, and various para-acetoxylated sulfonamide derivatives had been generated in excellent yields. This chemistry endowed an economic synthesis of valuable acetoxylated sulfonamides through direct C–O bond formation processes.     

Synthesis,photophysical and electrochemical properties of novel 6,12-di(thiophen-2-yl) substituted indolo[3,2-b]carbazoles

Novel 5,11-dialkyl-6,12-di(thiophen-2-yl) substituted 5,11-dihydroindolo[3,2-b]carbazoles have been obtained and plausible ways for their further modifications via the Friedel–Crafts reaction are presented. The formylation of these indolo[3,2-b]carbazoles with dichloromethyl alkyl esters catalysed by Lewis acids leads to the formation of the corresponding 2,8-diformyl derivatives. Applicability of this formylation method for modification of indolo[3,2-b]carbazoles bearing electron-rich aromatic substituents at C-6 and C-12 has also been demonstrated. The Knoevenagel condensation of 2,8-dialdehydes with active methylene nitriles has been studied. The measurements of optical and redox properties for a number of new indolo[3,2-b]carbazoles have been performed.     

Studies of some hydrogenated thiazolo[2,3-a]isoquinoline S-oxides

Several hydrogenated thiazolo[2,3-a]isoquinolinone S-oxides have been prepared and their stereochemistry established on the basis of spectral data analysis combined with X-ray crystallography. A reversible syn/anti isomerization of diastereomeric sulfoxides has been postulated to occur via a 10b proton abstraction.     

Auxiliary strategies for the preparation of β-amino alcohols with reductive cross-coupling and a synthesis of (−)-cytoxazone

Imine auxiliaries including chiral N-tert-butanesulfinyl imines have been successfully utilized to provide stereochemical control to the reductive cross-coupling of imines with aldehydes or ketones. This methodology has been applied to the synthesis of (−)-cytoxazone.     

Synthesis of substituted benzimidazo[2,1-a]isoquinolines and its condensed analogues using Pd(0)-catalyzed cyclization/C-H activation

An efficient route for the synthesis of benzimidazo[2,1-a]isoquinolines and its condensed analogues has been developed via the palladium-catalyzed cyclization/C-H activation of N-allyl and N-methallyl derivatives of benzimidazoles.     

An expedient stereoselective synthesis of (Z)- and (E)-allyl iodides from Baylis-Hillman adducts along with selective iodination of benzylic alcohols using the polymethylhydrosiloxane-iodine system

A stereoselective method has been developed for the synthesis of (Z)- and (E)-allyl iodides from Baylis-Hillman adducts using polymethylhydrosiloxane (PMHS) and iodine in chloroform at room temperature. In addition, the reagent system has been utilized for the iodination of benzylic alcohols selectively.     

A new entry to functionalized cycloalkylamines: diastereoselective intramolecular amidoalkylation of N,O-acetal TMS ether possessing allylsilane

Highly diastereoselective cyclization (>20:1) as a new entry to functionalized cycloalkylamines has been conducted with acyclic N,O-acetal TMS ethers possessing an allylsilane moiety.     

Synthesis of modified Weinreb amides: N-tert-butoxy-N-methylamides as effective acylating agents

An efficient preparation of N-methyl-O-tert-butylhydroxylamine hydrochloride has been settled, which allowed the synthesis of modified Weinreb amides. Nucleophilic addition of organolithium and Grignard reagents on these N-tert-butoxy-N-methylamides afforded efficiently the corresponding ketones and reduction with DIBAL furnished the corresponding aldehydes in good yields up to 97%.     

Elaboration and structural studies of cyclo 1:1-[α/α-N-amino]mers

In order to investigate the ability of self-organization of the alternance of α-amino and α-N-amino-acids the synthesis of cyclo 1:1-[α/α-N-amino]mers has been achieved by an iterative sequence of deprotection and coupling reactions followed by a macrocyclization step. The self-assembling of N-amino deprotected cyclo-oligomers has been characterized using X-ray diffraction experiments and FT-IR analysis.     

Platypodiol a novel clerodane diterpene from Baccharis platypoda

There is an urgent need for effective leishmanicidal drugs to replace or supplement those in current use. Our group has been bioprospecting many Brazilian plants looking for potential new ‘hits’ to combat leishmaniasis. We found that Baccharis platypoda was one of the Asteraceae species that displayed leishmanicidal activity. We now describe the isolation of the new clerodane diterpene (1), named platypodiol after its ethanolic leaf extract. Its structure was determined by detailed NMR and ESI-TOF/MS/MS experiments. Considering the few publications about this species, this result has increased the phytochemical knowledge about B. platypoda.     

Heteroaromatic annulation studies on 2-[bis(methylthio)methylene]-1,3-indanedione: efficient routes to indenofused heterocycles

2-[Bis(methylthio)methylene]-1,3-indanedione has been shown to be a useful three carbon 1,3-dielectrophilic synthon for the highly efficient regiospecific synthesis of a variety of indenofused five- and six-membered heterocycles via heteroaromatic annulation. The methodology has been further elaborated to the corresponding N,S-acetals leading to amino substituted heterocycles, thus providing further point of diversity in the newly synthesized heterocyclic frameworks. Further, the facile access to cytotoxic indeno[2,1-c]quinolin-7-ones and the novel polycyclic heteroaromatics demonstrates the versatility of heteroaromatic annulation protocol via α-oxoketene-S,S-acetal in generating novel biologically important polycyclic heteroaromatics.     

Substituent directed regioselective synthesis of 2-oxonicotonic acids and methyl nicotinates

An innovative synthesis of aryl tethered 1,2-dihydro-2-oxopyridine-3-carboxylic acids has been developed through nucleophile induced ring transformation of methyl 6-aryl-4-methylsulfanyl-2H-pyran-2-one-3-carboxylates using either cyanamide or arylamidine in excellent yields. Further, the reaction of methyl 6-aryl-4-methylsulfanyl-2H-pyran-2-one-3-carboxylates with formamidine acetate under analogous reaction conditions did not follow the same course of reaction and produced methyl nicotinate, regioselectively, in good yield. Decarboxylation of a 6-aryl-4-methylsulfanyl-1,2-dihydro-2-oxopyridine-3-carboxylic acid has been achieved by heating in PPA. The 4-methylsulfanyl substituent in 3 has also been oxidized to the corresponding methylsulfonyl group with m-chloroperbenzoic acid.