Letters in Organic Chemistry - Volume 8, Issue 7, 2011

Treatment of thia analogues of protoberberine alkaloids, 13-carboxy-13,13a-dihydro-6H,8H-isoquinolino [2,3-c][1,3]benzothiazin-8-ones, with thionyl chloride, followed by ethanol, unexpectedly provided 5,11-dioxoindeno [1,2-c]isoquinoline derivatives containing a novel ring system. Elucidation of their structures is presented in this paper. The antiproliferative effects of thiaprotoberberines and indenoisoquinolines were determined by MTT assay against a set of human adherent cancer cell lines (Hela, MCF7 and A431).

Two series of dendritic tryptophan derivatives have been synthesized and characterized, their emission spectra in different solvents and the reactivity of tryptophan were investigated and compared. There was a progressive shielding effect of the tryptophan in the emissive wavelengths of dendrimers increased with the size or generation of the dendritic shell.

Copper perchlorate hexahydrate is found to be an efficient catalyst for the electrophilic substitution of indole with carbonyl compounds to prepare bis(indolyl)methane derivatives without solvent in excellent yield at room temperature.

2-substituted benzimidazoles have been synthesized in a single pot from aromatic aldehydes and ophenylenediamine catalyzed by FeCl3/Al2O3 in DMF under ultrasonic irradiation and afforded good yields in a short period of time.

Citric acid was used as green, non-toxic and reusable catalyst for the preparation of substituted 2,3- dihydroquinazolin-4(1H)ones in high purity and good yields via one-pot three-component reaction of isatoic anhydride with a variety of aldehydes and primary amines or ammonium acetate in water at 80 ° C.

A novel, solvent free and efficient one pot synthesis of 1, 4-dihydropyridine derivatives was achieved in good yields via three component reaction of aldehydes, ethyl acetoacetate and ammonium acetate using inexpensive β- cyclodextrin as a supramolecular catalyst. The catalyst can be recovered and reused without loss of activity.

A mild and efficient method for the chemoselective preparation of 1,1-diacetates catalyzed by 1-methyl-3-(3- sulfopropyl)-imidazolium methyl sulfate under ultrasound irradiation has been developed. The yields are ranged in 90% ∼ 98%. This protocol offered several advantages including low catalyst loading, high yields, short reaction time and environmentally benign approach.

The reactions of some 1,3-dicarbonyl compounds with 9-benzylidene-9-H-fluorene derivatives in the presence of manganese(III)acetate and ceric ammonium nitrate (CAN) were searched. 9-benzylidene-9-H-fluorene compounds form mainly [2+3] dipolar cycloaddition products such as dihydrofuran and lactone which are spirally attached to the C-9 position of flourene ring with manganese(III)acetate and oxidative addition products with CAN. The best yield of cyclization products was obtained from the reaction between 2c and 1a-c in both oxidants. The stereochemistry of the products 3d, 4d and 5d was only transformed which has coupling constant 13 Hz.

Green Chemistry is the design of chemicals and processes that reduce or eliminate the use and generation of hazardous substances, and consequently reduce the risk to human health and the environment. Nitrones have various applications, such as building blocks in the synthesis of natural and biologically active compounds and molecular weight regulators in radical polymerization. In this work, dinitrones were successfully synthesized in a one-pot process from primary diamines and proper aromatic aldehydes employing methyltrioxorhenium (MTO) as catalyst and urea-hydrogen peroxide adduct (UHP) as oxidizing agent. Diamines, such as 1,6-diaminohexane and 1,12-diaminododecane were reacted with benzaldehydes bearing various substituent, such as 4-chloro, 4-nitro, 4-methoxybenzaldehyde, and also furfural. The resulting N,N' -bis (benzylidene)-1,6-hexanediamine N,N' -dioxides or N,N' -bis (benzylidene)-1,12-dodecanediamine N,N' - dioxides (or substituted benzylidenes) were separated with 45-60 % yields. The main advantage of the one-pot process is the elimination of need for several separation and purification steps and reduction in consumption of chemicals and waste production. The products selectively were characterized by 1H-NMR, 13C-NMR, FT-IR spectroscopies, and elemental analysis (CHNS).

Some new substituted isatin (2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl)thiosemicarbazones were synthesized by reaction between 2,3,4,6-tetra-O-acetyl-bgr;-D-glucopyranosyl thiosemicarbazide and corresponding substituted isatins using conventional and microwave-assisted heating method. It is shown that the latter gave higher yields of products.

Glycerol was successfully used as a green solvent and as an acyl acceptor in the transesterification of benzyl acetate using representatives' soluble and solid base catalysts. It was found that increasing the reaction temperature, the reaction time, the substrate concentration or the catalysts loading increased the yield of benzyl alcohol. Using glycerol as a solvent also enabled the separation of product by simple extraction with diethyl ether and catalyst recycling.

Corey-Chaykovsky epoxidation is one of the versatile methods for synthesis of structurally diverse oxiranes. The extension of simplified Corey-Chaykovsky epoxidation has been investigated. Ketones and aromatic aldehydes were epoxidized in satisfactory to excellent yields with trimethylsulfonium iodide as an ylide precursor and crushed potassium hydroxide as a base in tertiary butanol. The scope and limitation of the simplified procedure were examined. The results revealed that the procedure is applicable to the epoxidation of ketones and aromatic aldehydes.

An efficient and simple method for the synthesis of new deoxycholic acid thiosemicarbazone derivatives under solvent-free conditions using microwave irradiation has been developed. Its main advantages are short reaction times, good conversions, highly selective and the environment friendly nature of the process. Their structures were elucidated by IR, 1H NMR, ESI-Mass and elemental analyses. The preliminary results indicate that some of these compounds possess inhibitory effects against Escherichia coli.

The Michael addition of malonates to aromatic α,β-unsaturated aldehydes was efficiently organocatalyzed by (S)-2-[bis(3,4,5-trifluorophenyl)trimethylsilanyoxymethyl]pyrrolidine, derived from L-proline to afford the corresponding adducts in good yields with good to excellent enantioselectivities.

3-Substituted indolin-2-one derivatives had been designed and synthesized as a novel class of protein tyrosine phosphatase 1B (PTP1B) inhibitors. These compounds had been evaluated for their inhibitory activities against PTP1B in vitro with IC50 values in a low micromolar range. Compound 36, the lowest, bore an IC50 value of 3.48 µ M. Preliminary structure-activity relationship was summarized.