Letters in Organic Chemistry - Volume 11, Issue 4, 2014

Sixteen substituted curcumin analogs are synthesized in one pot by iodine impregnated nano neutral alumina catalyst under microwave irradiation. This catalyst shows higher reactivity by which it offered the reaction with higher yields and less reaction time. The prepared catalyst was characterized by FE-SEM, EDX and BET isotherm surface area. Also, the synthesized products were characterized by FT-IR, 1H NMR, 13C NMR, mass and elemental analysis.

A simple and efficient catalytic method has been designed for the synthesis of a series of novel β-aminoketones using 3-aryl-4-formylsydnone, primary aromatic amine and cyclohexanone in the presence of ceric ammonium nitrate (CAN). The percentages of syn and anti isomers formed were elucidated using 1H NMR spectral studies. The anti isomer was the major product.

A new aromaticity index has been proposed based on the energy of π orbital {-[π1+Σ2n(π1-πn)]x103} where n is the number of occupied π orbitals. Calculations have been performed on aromatic and heteroaromatic compounds using DFT method at B3LYP/6-311G+(d,p) level. This index has been tested on 6π electron compounds, on bicyclic and polycyclic aromatic compounds and compared with HOMA, the molar magnetic susceptibility (XM), and the aromatic stabilization energy (ASE). In all the cases, a good correlation has been found.

A novel analogue of unit A of cryptophycin-1 was prepared starting from commercial trans-cinnamaldehyde. The modifications introduced into the new structure related to the replacement of the epoxide with an aziridine moiety, and the inclusion of the 1,3-enone moiety into an aromatic ester frame through the synthesis of a key aromatic ketone. Asymmetry was induced during the later steps of the synthetic pathway. The optical purity of compounds was monitored by chiral HPLC and polarimetric measurements.

Xylose was found as a natural, cheap and efficient organocatalyst for the one-pot synthesis of substituted dihydropyrrol- 2-ones via a four-component domino reaction between amines, dialkyl acetylenedicarboxilates and formaldehyde. This protocol includes some important aspects like mild reaction conditions, good yields, short reaction times, affordable procedure, simple work-up and lack of need for column chromatography.

Dehydroacetic acid (DHA) and its simple derivatives find many interesting applications in the synthesis of various heterocyclic compounds of potential biological interest. A variety of DHA based chemical reactions were found to be useful in the synthesis of 3-cinnamoyl-4-hydroxy-6-methyl-2-oxo-2H-pyrans i.e. Chalcone analogues of DHA, pyranopyrazoles, substituted pyrones, 2H-Pyran and 2H-pyridine-2-ones, pyrimidines, pyrazoles, thiazoles, and pyridazines etc. The present review focuses on the synthetic and biological potential of DHA and provides update on the literature survey upto 2013.

A one-pot efficient procedure for the synthesis of 2, 4, 5-triaryl-1H-imidazole derivatives by the reactions of hexamethyldisilazane and arylaldehydes in the presence of N-bromosaccharin (NBSa) is studied. This new method offers several advantages, such as excellent yields, easy workup, short reaction times, and simple procedure.

A series of novel 2-((1-substituted-1H-1,2,3-triazol-4-yl/3-substitutedisoxazol-5-yl)methoxy) substituted pyridine, 1-((1-substituted-1H-1,2,3-triazol-4-yl/3-substitutedisoxazol-5-yl)methyl)substituted pyridin-2(1H)-one was prepared from 2-oxo-6-phenyl/methyl-4-(trifluoromethyl)-1,2-dihydropyridine-3-carbonitrile 3 via propargylation followed by 1,3- dipolar cycloaddition of the propargyl derivatives 4 and 5. These triazole/isoxazole tagged pyridine derivatives were evaluated for antitumor activity against breast cancer cell lines such as MDA-MB-231, MCF-7 etc. The results indicated that compounds 6e, 6f, 8e and 8f were found to be active on MDA-MB-231, while 6h and 8h were active on MCF-7.

Green synthesis of novel compounds 4-(2-carboxybenzamido)-2-hydroxybenzoic acids 3a-3e, 4-(1, 3- dioxoisoindolin-2-yl)-2-hydroxybenzoic acids 4a-4e, 2-acetoxy-4-(2-carboxybenzoylamino)benzoic acids 6a-6e and 2- acetoxy-4-(1, 3-dioxo-1, 3-dihydroisoindol-2-yl)-benzoic acids 8a-8e has been developed which were analogs of aspirin (used as analgesic, anti-pyretic and cardiovascular drug) and para-aminosalicylic acid ( used as anti-tuberculosis agent).

The synthesis and thermocyclization of linear Gramicidin S precursor analogues (LGSA) were presented. CD spectra suggested that synthesized LGSA adopt a pleated β-sheet structure that is stabilized by intramolecular hydrogen bonds. Both Dphe6 and Pro7 residues were found to play an important role in maintaining the β-sheet conformation of LGSA. Our results indicate that unactivited LGSA, with the preorganized β-sheet structure, can be efficiently cyclized into the corresponding head-to-tail cyclic products in high yield after being heated under solvent-free conditions.