Letters in Organic Chemistry - Volume 7, Issue 6, 2010

A screening of different metal triflates as catalysts was performed to get isochromans through an oxa-Pictet- Spengler reaction. Good to high yields were obtained for various aliphatic or aromatic aldehydes and β-arylethanols. A mechanism involving catalysis by in situ liberated triflic acid to catalyse the isochroman ring formation is proposed.

The chiral monoaza-15-crown-5 lariat ethers annellated to methyl-4,6-O-benzylidene-α-D-glucopyranoside- (1) or -mannopyranoside (2) used as phase transfer catalysts in the Michael addition of 2-nitropropane to substituted chalcones and chalcone analogues resulted in a significant asymmetric induction. The type of substituent on the chalcone molecule was found to have a significant influence on both the chemical Read More

The electronic reorganization along the [3+2] cycloaddition (32CA) reaction of the simplest azomethine ylide (AY) with ethylene has been studied using the topological analysis of the ELF at the B3LYP/6-31G(d) level of theory. This 32CA reaction, which has a negligible barrier (1.2 kcal/mol), takes place through a synchronous concerted transition state structure. The analysis of the ELF stresses that the pseudo-diradical chara Read More

Various 2-iodomethyl-N-tosylindolines are obtained in high yields from the reaction of N-tosyl-2-allylanilines with iodine in water at 50°C.

Refluxing 2-Aryl-2,2'-biindan-1,1',3,3'-tetrones in acetic acid with urea produces 3-amino-2-(2'- arylindanedionyl)indenones regioselectively within 2-3 h. in good yields. X-ray crystal structures of the products clearly indicate that in the solid state the compounds exist in the keto form. On the other hand NMR studies reveal that the enaminones exist in keto form in CDCl3 and in enol form in DMSO-d6 and acetone-d6.

A novel protocol for the semi-synthesis of docetaxel was achieved in four steps from 10-deacetyl baccatin III with an overall yield of 50%. The key step is the selective protection of the C(7) and C(10) hydroxyl groups of 10- deacetyl baccatin III, utilizing benzyl chloromate as a selective protecting reagent, which are capable of being conveniently removed by Pd/C under hydrogen atmosphere.

A new series of quinoxalinic oxirane derivatives was synthesized from reaction between 2-(dibromomethyl) quinoxaline and α-dicarbonyl compounds using tetrakis(dimethylamino)ethylene (TDAE).

A stereoselective and convergent formal approach to Salicylihalamide A and B is achieved through our recently developed strategy for the construction of polyketide precursors via Prins cyclisation. The approach mainly relies upon reductive opening of 1-iodomethyl cyclic ethers, Mitsunobu inversion and ring closing metathesis along with Prins cyclisation.

A series of novel prolinamide organocatalysts based on calix[4]arene scaffold have been developed to catalyze the direct asymmetric aldol reaction of aromatic aldehydes and cyclohexanone. Under the optimal condition, high isolated yields (up to > 99%) and enantioselectivities (up to 97% ee), and moderate diastereoselectivities (up to 85/15) were obtained.

A novel one-pot four-component synthetic method for 3-(1,3,4-thiadiazol-2-ylamino)-3-arylpropanoates by condensation of 2-amino-1,3,4-thiadiazoles, aldehydes, Meldrum's acid and aliphatic alcohols catalyzed by p-toluenesulfonic acid was described. The protocol has advantages of mild conditions, high yield and simple work-up procedure.

Pyrrolizidines were synthesized from 1,3-dipolar cycloaddition of N-substituted isatins, proline, and olefins. The highly diastereoselective and regioselective one-pot three-component cyclocondensation products were obtained in the presence of ionic liquids such as 1-buthyl-3-methlylimidazolium bromide.

Asymmetric hetero Diels-Alder (HDA) reaction of highly reactive acyl nitroso intermediates are reported. Transient acyl nitroso compounds 2a'-c' are formed by Ru(II)- or Ir(I)-catalyzed hydrogen peroxide oxidation of hydroxamic acids 2a-c and are trapped in situ by the optically pure N-dienyl-L-pyroglutamates 1a-b to afford the corresponding diastereomeric adducts 3a-f and 4a-f up to 98% yield (70% de) and 72% de (70% yiel Read More

We report in this paper the regioselective synthesis of functionalized oxime ethers 3 in good yields from the reaction of readily available starting material oximes with allyl bromides, derived from Baylis-Hillman adducts, in the presence of sodium hydride and triethyl amine under mild condition.

Enaminones were efficiently prepared via modification for Gupton method, which depends on carrying out the latter procedure in one step reaction, avoiding the isolation of [3-(dimethylamino)-2-azaprop-2-en-1- ylidene]dimethylammonium chloride (Gold's reagent) (5) which is prepared in situ from cyanuric chloride (4) then it reacts successfully with ketone 1a-j to produce the enaminones 3a-j in suitable yields. The modif Read More

Seven novel 6-(1-acetyl-3-methyl-4,5-dihydro-1H-pyrazol-5-yl)-2-amino-4-substituted-phenyl-4H-chromene- 3-carbonitrile derivatives were synthesized and characterized by ESI-MS, 1H NMR and 13C NMR. All of the compounds have been screened for their antibacterial activity. The results show that compounds 7e and 7f displayed significant activity with MIC of 1.562 μg/mL against B. subtilis ATCC 6633.

An efficient oxidation of benzyl halide has been done using aqueous hydrogen peroxide (30%) in trihexyl(tetradecyl)phosphonium-tetrafluroborate ionic liquid the protocol is simple mild offering excellent yield of product.

A new type of perylenebisimide-based imidazolium chemosensor was synthesized for selective recognition of anions. Imidazolium-anchored receptor PBI-1 showed high binding affinity to F- due to the role of the phenolic hydroxyl group as an additional binding site. The hydroxyl-protected receptor PBI-2 could serve as highly selective and sensitive colorimetric and fluorometric sensor for H2PO4-. The study indicated that th Read More