Water-mediated,green, and efficient synthesis of bisquinolones under catalyst-free conditions

Water-mediated, green, and efficient synthesis involving condensation of 4-hydroxy-1-methylquinoline-2(1H)-one (3) with different aromatic and heterocyclic aldehydes (4a–n) leading to 3,3′-(arylmethylene)-bis-(4-hydroxy-1-methylquinolin-2(1H)-one) 5(a–n) under catalyst-free conditions is described. This reaction has an easy workup without using column chromatography and provides excellent yields of the products in shorter reaction times. It does not require any catalyst and uses water as the medium which is the greenest solvent. 3 required in this work was itself obtained by condensation of N-methylaniline (1) with malonic acid (2) in the presence of POCl₃ using a previously reported procedure.     

Total synthesis of (±)-sacidumlignan D

The first total synthesis of (±)-sacidumlignan D featuring a Zn-mediated Barbier reaction and reverse Wacker oxidation to form the key γ-lactone, its diastereoselective α-methylation followed by reduction cyclization, was documented.     

Divergent Pd(II) and Au(III) mediated nitroalkynol cycloisomerizations

A new cycloisomerization reaction comprising the simultaneous addition of nitro and alcohol groups across C≡C leading to skeletally diverse small molecules is documented.     

Titanium(IV)-promoted regioselective nucleophilic ring-opening reaction of chiral epoxyallyl alcohols with acids as a tool for ready access to chiral 1,2,3-triol monoesters: application to stereoselective total synthesis of macrolides

Titanium(IV)-promoted regioselective ring-opening reaction of chiral epoxy-allyl alcohols (Sharpless conditions as the key strategic step) is developed as a tool for ready access to chiral 5,6-dihydroxyoct-7-en-4-yl alkoxylates. Later, the synthetic utility of products thereof was demonstrated through the RCM based stereoselective synthesis of various natural products.     

Total synthesis of (-)-sacidumlignans B and D

The first total synthesis of naturally occurring sacidumlignans A (1), B (2), and D (4) was executed and the absolute configuration of 2 and 4 was determined. A diastereoselective α- methylation of a lactone was used as the key step for the control of the chiral centers of the central lignan core. An acid mediated dehydrative cyclization of an aldehyde to construct the dihydronaphthalene unit of 2 and the aromatization of the intermediate dihydronaphthalene derivative to synthesize 1 are the key reactions employed in this regard.     

Low-temperature synthesis of morphology controlled metastable hexagonal molybdenum trioxide (MoO3)

We demonstrate a simple low-temperature chemical method to produce metastable hexagonal MoO₃ phase nanorods. The structure, chemical purity, thermal stability and optical properties of hexagonal MoO₃ are reported. Our results provide a more direct method to produce high quality and stable hexagonal MoO₃, which exhibits phase stability up to 400 ^°C at which point an irreversible phase transition occurs to form orthorhombic MoO₃.     

Glycal-ruthenium carbonyl clusters: Syntheses, characterization, and anticancer activity

Four new chiral ruthenium carbonyl cluster complexes Ru₃(μ-H)₂(CO)₉(L-2H) (1), Ru₃(μ-H)₂(CO)₇(L-2H)(dppm) (2), Ru₃(μ-H)₂(CO)₇(L-2H)(PPh₃)₂ (3), Ru₃(μ-H)₂(CO)₇(L-2H)(dppe) (4) containing a dehydrogenated form (L-2H) of 3,4,6-tri-O-benzyl-d-galactal (L) as a chiral ligand have been prepared and characterized. The anticancer activity of five compounds 1-4 and Ru₃(μ-H)₂(CO)₉(L-2H) 5 (L = tribenzyl glucal) against six types of human cancer cell lines was studied and compared to cisplatin. Compound 1 was chosen to produce more detailed growth curves based on overall highest activity profile. The structure of compound 2 was established by a single-crystal X-ray diffraction analysis. The structure based on triangular metal framework contains a bridging dehydrogenated tribenzyl galactal ligand bonded in a parallel μ₃-η²-bonding mode and a bridging dppm ligand. Variable-temperature NMR studies show that the two hydride ligands in compounds 1 and 2 are dynamically active on the NMR time scale at room temperature.     

Halogen-substituted amides. VI—vibrational spectra of some fluoro- and iodo-substituted acetamides

The Raman spectra of 2-fluoroacetamide, trifluoroacetamide and 2-iodoacetamide were recorded and their infrared spectra as mulls were measured in the range 4000–200 cm⁻¹. The Fourier transform far-infrared spectra of the same samples, in the region 500–50 cm⁻¹, were also obtained. The frequencies were assigned to various fundamental modes of the molecules on the basis of qualitative considerations.     

Silica gel catalyzed α-bromination of ketones using N-bromosuccinimide: An easy and rapid method

An easy and rapid method for the a-bromination of ketones using N-bromosuccinimide(NBS) catalyzed by silica gel in methanol under reflux conditions was developed. The expected products were formed in excellent isolated yields within a short period of time(5–20 min). Major advantages of the present procedure include use of inexpensive and readily available catalyst, exclusion of pre- and post-chemical treatment of catalyst and use of methanol as solvent instead of ethers and chlorinated solvents.