Letters in Organic Chemistry - Volume 9, Issue 8, 2012

Purpurin, 1,2,4-trihydroxyanthraquinone, was regioselectively alkylated under basic conditions using bromoalcohol of varying chain length. As a base, potassium carbonate, tetrabutylammonium hydroxide or 1,8- diazabicyclo[5.4.0]undec-7-ene (DBU) was used. The reaction of alkylation proceeded exclusively on the 2-hydroxyl group of the purpurin molecule. Addition of the obtained 2-(ω-hydroxyalkoxy)purpurins to protected D-glucal catalysed by triphenylphosphine hydrobromide gave an access to new glycoconjugates with high enantioselectivity. In parallel experiments, the same substrates reacted in the presence of boron trifluoride etherate yielding the appropriate unsaturated adducts as a result of Ferrier rearrangement.

A novel diepoxide containing paracyclophane was synthesized by peracid oxidation of a known paracyclophane diene. The resulting diepoxide was characterized. It was investigated as a potential monomer for a cyclophane containing polyether by cationic ring opening polymerization. None of the standard catalyst systems for such a polymerization were successful in producing polymer.

To investigate the antitumor activities of xanthonic compounds, 10 prenylated xanthone derivatives 2-11 along with their key building block 1,3,6-trihydroxyxanthone 1 were evaluated for their potential cytotoxic activities against HeLa and MDA-MB-231 cancer cell lines. The synthesis afforded a series of prenylated derivatives with typical and new xanthone skeletons. Compounds 2, 3, 4 and 9 were reported for the first time to possess a new scaffold of 2H-xanthene- 3,9-dione. Interestingly, analogues 2 and 3 with the new scaffold demonstrated remarkable in vitro growth inhibitory activities against both the cell lines by displaying a greater cytotoxic potency than the standard drugs used in the assay, namely doxorubicin and cisplatin. In contrast, a dramatic loss of activity was observed for the O-prenylated derivatives 9- 11. These findings have highlighted the therapeutic potential of 2H-xanthene-3,9-dione scaffold to be exploitable as drug lead with specific activity against cervical and breast cancers.

The novel dihydropyranyl-functionalized resins, referred to as “JJ-DHP”, prepared from JandaJel-Cl resin, have been developed. We have also clarified that JJ-DHP has shown a good swelling property in common organic solvents and reusable ability in solid-phase organic synthesis.

We successfully prepared a novel supramolecular network complex having one-dimensional (1D) channel-like cavities by using 2-naphthylethylamine and 2,2'-bithiophene-5,5'-dicarboxylic acid. The EtOH molecules in this complex were trapped as guests in 1D channel-like cavities formed by the assembly of characteristic two-dimensional (2D) layered hydrogen- and ionic-bonded network structures.

The Pd(II)-catalyzed cyclization of hydroxyl-substituted allylic alcohols quantitatively afforded a cis/trans mixture of 2,5-substituted tetrahydrofurans.

The regioselective synthesis of the 3,4,5-trimethoxy-2-(3,4-methylenedioxy-6-nitrophenyl)benzaldehyde as key intermediate for divergent preparation of cytotoxic biaryl lignans was achieved in three steps from commercially available starting materials. Reactivity of this synthon was illustrated by its conversion into the corresponding phenanthridine and bromomethylbenzene.

The first efficient organocatalytic conjugate addition reaction of 2-arylacetates and 2-arylacetonitriles having an electron-withdrawing group to nitroalkenes has been achieved using a bifuctional amino thiourea catalyst. The reagents having NO2-, CO2Me-, and CN-functional groups on the aromatic ring can be used; the bifuctional catalyst 4i provided Michael adducts in the reaction of various nitroalkenes with broad generality in high yield and diastereoselectivity.

The solid-phase synthesis of allosamidin and its analogue di-N-acetyl-β-chitobiosyl NAG-thiazoline were investigated. The synthesis was performed using polystyrene as support and o-nitrobenzyl ether tether as linker. The target allosamidin 1 and di-N-acetyl-β-chitobiosyl N-acetylglucosamine (NAG)-thiazoline 2 were efficiently obtained by iterative glycosylation reactions, catalytic hydrogenation, acetylation, deacetylation, and photolysis, respectively.

Three-component condensation reaction of an aldehyde with β-ketoester and urea or thiourea in acetonitrile to afford the dihydropyrimidinones and thions (DHPMs) in the presence of 22% Co/CeO2-ZrO2 nano fine particle as a novel, reusable and green catalyst is reported. Utilizing of 22% Co/CeO2-ZrO2 nano fine particle catalyst also offers a cleaner process in that it can be reused and will not bring additional pollutants into the “environment” that is agreeable green chemistry point of view.

In the present paper, the coupling reaction of aldehyde, terminal alkyne, amine salt and CO2 was investigated. Copper iodide was found to be an efficient catalyst for the coupling reaction in ethyl acetate at 80 °C and under an atmospheric pressure of CO2. A diverse range of oxazolidinones was prepared by this method. Subsequently, a copper-catalyzed coupling of aldehyde, terminal alkyne, diamine salt and CO2 was developed to generate a dioxazolidinone. Finally, under the optimised conditions, we report for the first time a facile synthetic route for the synthesis of polyoxazolidinone, a new polyurethane, via a multi-component coupling of benzaldehyde, 1, 4-diethynylbenzene, 1, 6-hexadiamine and CO2.

Reaction of 3-acetyl and 3-bromoacetyl coumarins with hydrazine hydrate has resulted in the ring opening of the coumarin moiety. The reaction was attempted with a view to obtain some new pyridazinones and pyrazolones. The reaction did not proceed via the expected pathway instead led to the formation of salicyl azines, the structure of which has been confirmed by single crystal X-ray studies.

Silica bromide as heterogeneous reagent is prepared from the reaction of silica gel with PBr3 as a nonhydroscopic, filterable, cheap, and stable yellowish powder that can be stored for months. The results show that the silica bromide is a suitable and efficient reagent for conversion of alcohols to alkyl bromides under mild conditions at room temperature. The easy availability of this reagent makes this simple procedure attractive and a practical alternative to the existing methods.

A rapid and efficient method for the synthesis of novel chenodeoxycholicacid acid thiosemicarbzones under solvent-free conditions using microwave has been developed. Their structures were elucidated by ESI-MS, IR, 1H NMR and elemental analysis. Nine novel compounds have been synthesized in good yields. Compared to the conventional method, microwave irradiation method, main advantages are short reaction times, good conversions and the environmentally friendly nature of the process. Preliminary results showed that some of these compounds possess inhibitory effects against S. typhimurium and E. coli.

An efficient and simple method for the preparation of 3,3',5,5'-tetra-tert-butyl-4,4'-diphenoquinone (TBDPQ) is reported using Lewis Acid as an effective catalyst in the presence of molecular oxygen from 2,6-di-tert-butylphenol (DBP). The present methodology offers several advantages, such as excellent yields, accessible and inexpensive catalysts, easy work-up and green conditions. The oxidation reaction was found to proceed in two steps and the oxidation kinetics for FeCl3 system was examined in detail.