Letters in Organic Chemistry - Volume 5, Issue 8, 2008

Under solvent-free condition the addition of dimethyl malonate (1) to (E)-β-nitrostyrenes 2a-j proceeds smoothly in the presence of 2.5 mol% of 6'-hydroxy cinchonine (QD-OH) and equimolar amounts of reagents at 30 °C. The corresponding products 3a-j are obtained with satisfactory enantiomeric excesses (68-88%) and high yields (70- 92%).

Simple, clean, environmentally friendly procedures for the solvent-free preparation of coumarins, dihydrocoumarins, flavones and chromones under microwave heating are described. Silica-supported Wells-Dawson heteropolyacid (H6P2W18O62·24 H2O) was employed as catalyst. High selectivity, very good yields and short reaction times were obtained. The results are compared with those of the reactions performed under conventional heating.

The Kabachnik-Fields reaction may be carried out under a variety of conditions. More recently, the application of “exotic” catalysts, in most cases in traditional solvents and a few instances in ionic liquids, came into fashion. Using a pool of simple model compounds, still extending the scope of the reaction under discussion, it is shown that the simplest, most straightforward and most environmentally friendly accomplishment of the condensation of the oxo-component, the amine and the >P(O)H species to afford α-aminophosphonates or phosphine oxides involves microwave irradiation of the neat reaction mixture without the use of any catalyst. In some cases, the reaction is more clear-cut if the title compounds are prepared by a two-step one-pot procedure.

The present paper describes a mild and efficient method to synthesize 3-aminosubstituted isothiazole sulfoxides taking advantage of arylsulfonyloxaziridines. The reactivity of the resulting isothiazole sulfoxides toward sulfur nucleophiles has been studied and resulted in the formation of 5-sulfanylsubstituted isothiazoles in a fully diastereoselective way. From 3-benzylamino-5-chloro isothiazole S-oxide an addition-elimination reaction took place affording smoothly the corresponding unsaturated 5-sulfanyl derivatives.

The Imino Diels-Alder reaction of N-benzylideneanilines with 3, 4-dihydro-2H-pyran and 2, 3-dihydrofuran proceeds smoothly to afford pyrano and furanoquinolines 3a-i and 4a-i in the presence of Antimony (III) Sulfate as catalyst. A concise and efficient synthetic route has been developed for one pot synthesis of pyrano and furano quinolines 6a-l and 7a-l by the reaction between anilines and 3, 4-dihydro-2H- pyran and 2, 3-dihydrofuran respectively in fairly good yields. This catalyst is inexpensive, easily available and it was also found that catalyst could be recovered quantitatively and reused without much loss of catalytic activity.

We report the synthesis and phytotoxicity of the compounds involved in the SRN1-Stille reactions such as methyl 2,5-diphenylbenzoate (6), methyl 5-chloro-2-phenylbenzoate (7) and methyl 2-methoxy-3,6-diphenylbenzoate (8) as well as the phytotoxicity of intermediates. 8 has a good herbicide activity compared to Disugran and it isn't a chlorinated compound.

Syntheses of diene based steroidal mimics of the estrogens, 2 and 3, were made through Wittig and McMurry reactions, as templates for estrogen receptor modulators.

Aminoalkyl phosphoramidates were obtained by either direct phosphorylation of symmetric diamines or a three steps method analogue to Gabriel's synthesis and coupled to a 4-oxoquinoline acyclonucleoside, in order to synthesize 4- oxoquinolone phosphoramidates. Two unpublished compounds demonstrated low cytotoxity in comparison to Acyclovir and good HSV-1 cytophatic effects on Acyclovir resistant strains.

Phosphomolybdic acid (PMA) supported on silica gel (SiO2) is found to catalyze efficiently the hydroamination of unactivated alkenes with sulfonamides to produce tosyl and mesyl protected secondary amines in excellent yields in short reaction times. The use of reusable solid acid catalyst, phosphomolybdic acid/SiO2 makes this method quite simple, more convenient, cost-effective and environmentally friendly.

Amberlyst-21, a kind of well-known and cheap polymeric material, was treated with ytterbium perfluorooctanesulfonate [Yb(OPf)3] giving a reagent with a ytterbium loading of 1.34 (wt %). The polymer-supported fluorous ytterbium catalyses the highly efficient synthesis of 1,5-benzodiazepine derivatives. The catalyst can be recovered by simple filtration under fluorous-solvent-free conditions and used again without a significant loss of catalytic activity.

An environmentally benign one pot synthesis of dihydropyridines and its use as hydrogen source in the reduction of α,β-unsaturated aldehydes and ketones using catalytic amount of BDMS at room temperature is described. An extensive study on the role of substituents on aldehyde for the formation of Hantzsch esters, reveals that presence of more than one electron donating substituents, hinders the formation of dihydropyridine derivative.

A novel method has been developped for synthesizing aryl ketones by means of I2-DMF mediated Friedel- Crafts acylation of aromatic substrates. The reaction is applicable to activated aromatic compounds. The present process is carried out under conditions involving minimal wastes and energy-consumption as compared to the use of molecular iodine.

An efficient and rapid procedure for the conversion of various carboxylic acid derivatives into the corresponding gem-bisallylated compounds under mild reaction conditions has been developed. Zinc-copper couple mediating Barbier- type addition of carboxylic acid derivative was utilized as a key operation to affect the transformation. The procedure is operationally simple, giving good to high product yield.

Optically pure secondary alcohols were efficiently prepared via a two-step, one-pot process involving a chemical oxidative agent in combination with an enantioselective ketone reducase Rhodotorula sp. AS2.2241 in tandem. The reaction proceeded successfully with 88∼99.5% enantiomeric excess in moderate to good conversions. A variety of substrates, including aromatic and aliphatic alcohols, could be tolerated.

The di-thioureas (1) and mono-thioureas (3) based on 1,1'-binaphthyl-2,2'-diol exhibited a preference for Cl- with a 1:1 stoichiometry. The cooperativity of the two binding sites (two thiourea groups for 1, thiourea and hydroxyl groups for 3) for anion binding was established by comparing the binding of the mono-thiourea receptors (2) based on naphthyl.

The SEM and XRD data show an unprecedented arc fabrication of spherical monoclinic crystals of nano dihydroxyacetone dimer (C6H12O6) from graphite, with a grape cluster morphology, in the size range of 40 to 150 nm, in the open air, providing another clue for the proposed arc discharge origin of organics and/or life.

Modification of A ring of 10-deacetylbaccatin III to get novel rearranged taxoids is described. The modification is achieved via manoeuvering of the C-11 double bond of 10-deacetylbaccatin III.

Butanoic moiety of 4-aryl-2,4-dioxobutanoic acids is involved in interactions with metal ions within HIV-1 integrase active site. Sixteen congeneric 4-phenyl-2,4-dioxobutanoic acid derivatives with different substitution on the phenyl ring were prepared. Effects of substitution were studied by spectrometric methods (NMR, MS, UV/VIS) and linear free energy relationships. Better metal complexation ability of meta-alkyl substituted compounds, was observed. This observation might have pharmacological implications.