Volume 23, Issue 2

Abstract: A series of 2-substituted and 2,3-disubstituted 5-cyanoindolizine derivatives were conveniently synthesized by a one-pot tandem reaction under mild conditions in moderate yields. The reaction mechanism was proposed.

3-Formylcoumarins 2 are formed as single products in high yields upon reduction of 3-cyanocoumarins 1 with Raney nickel in formic acid. The starting materials 1 are easily accessible by Knoevenagel condensation of commercially available salicylaldehydes.

Porphyrins are of interest in many applications that involve electron transfer and absorption of light, such as solar energy and photodynamic cancer therapy. The newly synthesized 5,10,15,20-tetrakis(3,4-dibenzyloxyphenyl)porphyrin, TDBOPP, was characterized using 1 H NMR, 13 C NMR, UV-vis and fluorescence spectroscopy and MALDI-TOF/TOF high resolution mass spectrometry. Standard 1 H NMR and 13 C NMR experiments coupled with nuclear Overhauser effect (NOE) experiments confirmed the structure of the compound. The expected M + and [M+H] + ions are observed in the MALDI-TOF/TOF mass spectrum. The UV-vis absorption spectrum of TDBOPP shows a Soret band at 424 nm and three Q bands at 519 nm, 556 nm, and 650 nm with molar absorptivity 3.6×10 5 cm −1 m −1 , 1.6×10 4 cm −1 m −1 , 1.0×10 4 cm −1 m −1 and 5.3×10 3 cm −1 m −1 , respectively. Excitation at 424 nm gives emission at 650 nm. The quantum yield of the porphyrin is 0.11.

A new stereoselective cascade reaction of benzylidenecyanoacetates and 1,3-dimethylbarbituric acid by the action of bromine in the presence of a base into substituted (barbituric acid)-5-spirocyclopropanes is described. The yields are in the range of 60%–75%. Nuclear magnetic resonance (NMR) studies indicate that this cascade transformation results in the stereoselective formation of spiro products with trans -configuration of aryl and alkoxycarbonyl substituents in the cyclopropane ring. The products are a perspective class of compounds with prominent pharmacological and physiological activity.

A one-pot cyclocondensation of 1,3-dioxane-5-one ( 1 ) with malononitrile and aromatic aldehydes in aqueous sodium hydroxide under ultrasonic irradiation furnishes a series of pyrano[3,2- d ][1,3]dioxin derivatives 3 . Reactions are completed after a few minutes and the precipitated products are purified by simple crystallization from ethanol. The reaction with ethyl cyanoacetate instead of malononitrile gives the respective analogous products in high yields.

A facile method for the synthesis of [1,2,4]triazolo[4,3- b ][1,2,4,6]thiatriazine 1-oxides 3a–h is presented. The approach involves a reaction between N -triazol-3-ylamidines 2a–h and thionyl chloride in the presence of pyridine. The structures of the synthesized compounds were confirmed by spectral studies including IR, 1 H NMR, 13 C NMR, MS and elemental analysis.

2-Cyano-substituted 1,4-benzothiazine 1,1-dioxides, required for antiviral studies, were prepared by a reductive cyclodehydration of an ortho -nitro sulfone precursor containing a pendant aryl ketone group. The ring-forming reaction also furnishes a non-cyclized benzamide as a major byproduct via an unexpected acyl transfer reaction.

2-Alkyl and 2-aryl-3-(phenylamino)quinazolin-4(3 H )-ones 4a–h were synthesized in a one-pot three-component condensation of an isatoic anhydride 1a–h , ethyl or methyl ortho ester and phenylhydrazine in the presence of KAl(SO 4 ) 2 ·12H 2 O (alum) as a nontoxic, reusable, inexpensive and easily available catalyst. The synthesis was conducted under microwave irradiation or classical heating. Products 4a and 4b show good antimicrobial activities.

A procedure for the preparation of the title salts via regioselective halocyclization of 3- S -propargylthio-4 Н -1,2,4-triazoles is reported. Stereoselectivity of electrophilic heterocyclization depends on the nature of the electrophilic reagent: bromination is better than iodobromination and iodination. The heterocyclization with tellurium tetrahalogenides leads to the formation of a mixture of geometric isomers of the salts. Their structure was confirmed by 1 H NMR, 13 C NMR, НМВС and single crystal X-ray diffraction analysis.

A single crystal of Ni(II)bis(3,4 dimethoxybenzoate)bis(nicotinamide) dihydrate, formulated as C 30 H 34 N 4 NiO 12 (I), was characterized in the solid state by infra-red (IR), ultra-violet (UV) and single crystal X-ray diffraction analysis at 296 K as mononuclear with a distorted octahedral stereochemistry. The complex consists of a six-coordinate Nickel atom in a distorted octahedral environment constructed from two N atoms and four O atoms and crystallizes in the monoclinic space group C 2/c with a =27.7680(16) Å, b =8.5748(3) Å, c =17.8018(9) Å, α=90°, β =108.154(4)°, γ=90°, Z =4. The molecular structure and geometry was also optimized using the B3LYP density functional theory method employing the 6-31G(d) basis set. The molecular electrostatic potential (MEP), frontier molecular orbitals (FMO) analysis, nonlinear optical properties (NLO) and natural bond analysis (NBO), Mulliken population analyis, natural population analysis (NPA) and Fukui function analysis were also described.

A series of chalcones 1–12 were converted to pyrazolines ( 1Pi–12Pi ) by reaction with phenylhydrazine followed by DDQ oxidation to produce the corresponding pyrazoles ( 1Pz–12Pz ). Three 1-phenyl-3- t -butyl-5-arylpyrazoles ( 13Pz–15Pz ) were synthesized using an analogous approach. Molecular modeling studies predicted the 5-aryl group of the pyrazoles for both series to have a torsion angle of 52°–54° whereas the 1-phenyl group was predicted to have 35°–37° torsion angles. The 3-aryl group was predicted to be essentially coplanar (−3°) with the pyrazole system in the first series. 13 C NMR data for both series, 1Pz–12Pz and 13Pz–15Pz , were collected in DMSO- d 6 at 50°C. A plot of the C4 chemical shifts for 1Pz–12Pz versus Hammet constants for 5-aryl substituents yielded a very good linear correlation (R 2 =0.96) with a slope of 1.5. The chemical shift data for C4 showed little or no dependence on 3-aryl substituents. The result for 13Pz–15Pz , despite only three points, was consistent with the first series results and yielded a ρ value of 2.0. Distal transmission of substituent effects (5-aryl groups) to C4 of the pyrazole system was reduced by roughly 50–60% of that of the analogous planar isoxazole system, but are not consistent with results for the similarly twisted 4-bromoisoxazoles.